Successful treatment of a cat with primary hypoadrenocorticism and severe hyponatremia with desoxycorticosterone pivalate (DOCP)

A 6-year-old, castrated male Siamese cat was diagnosed with primary hypoadrenocorticism, confirmed by an adrenocorticotopic hormone (ACTH) stimulation test documenting both hypocortisolism and hypoaldosteronism. The cat was successfully treated using a combination of prednisolone and desoxycorticosterone pivalate (DOCP). This case demonstrates that DOCP can be used successfully as mineralocorticoid supplementation in cats with hypoadrenocorticism and may have a longer therapeutic duration than that in dogs.

First evidence of the possible implication of the 11-deoxycorticosterone (DOC) in immune activity of Eurasian perch (Perca fluviatilis, L.): comparison with cortisol

Cortisol, the main corticosteroid in fish, is frequently described as a modulator of fish immune system. Moreover, 11-deoxycorticosterone (DOC) was shown to bind and transcriptionally activate the mineralocorticoid receptor and may act as a mineralocorticoid in fish. Immune modulations induced by intraperitoneal injections of these two corticosteroids were assessed in Eurasian perch juveniles. Cortisol and DOC were injected at 0.8 mg kg(-1) and 0.08 mg kg(-1) body weight respectively. Cortisol increased plasma lysozyme activity 72 h post-injection, C-type lysozyme expression in spleen from 1 to 72 h post-injection, and favoured blood neutrophils at the expense of a mixture of lymphocytes and thrombocytes. Moreover, 6 h after injection, cortisol reduced expression levels of the pro-inflammatory cytokine TNF-α in spleen. DOC had no effects on the immune variables measured in plasma, but increased expression levels of C-type lysozyme and apolipoprotein A1 mRNA in both gills and spleen. Meanwhile, DOC stimulated its putative signalling pathway by increasing expression of mineralocorticoid receptor and 11β-hydroxysteroid dehydrogenase-2 in spleen. These results confirmed the role of cortisol as an innate, short term immune stimulator. For the first time, DOC is described as a possible immune stimulator in fish.

Does glucocorticoid receptor blockade exacerbate tissue damage after mineralocorticoid/salt administration?

Mineralocorticoid receptor (MR) antagonism reverses established inflammation, oxidative stress, and cardiac fibrosis in the mineralocorticoid/salt-treated rat, whereas withdrawal of the mineralocorticoid deoxycorticosterone (DOC) alone does not. Glucocorticoid receptors (GRs) play a central role in regulating inflammatory responses but are also involved in cardiovascular homeostasis. Physiological glucocorticoids bind MR with high affinity, equivalent to that for aldosterone, but are normally prevented from activating MR by pre-receptor metabolism by 11beta-hydroxysteroid dehydrogenase 2. We have previously shown a continuing fibrotic and hypertrophic effect after DOC withdrawal, putatively mediated by activation of glucocorticoid/MR complexes; the present study investigates whether this effect is moderated by antiinflammatory effects mediated via GR. Uninephrectomized rats, drinking 0.9% saline solution, were treated as follows: control; DOC (20 mg/wk) for 4 wk; DOC for 4 wk and no steroid wk 5-8; DOC for 4 wk plus the MR antagonist eplerenone (50 mg/kg.d) wk 5-8; DOC for 4 wk plus the GR antagonist RU486 (2 mg/d) wk 5-8; and DOC for 4 wk plus RU486 and eplerenone for wk 5-8. After steroid withdrawal, mineralocorticoid/salt-induced cardiac hypertrophy is sustained, but not hypertension. Inflammation and fibrosis persist after DOC withdrawal, and GR blockade with RU486 has no effect on these responses. Rats receiving RU486 for wk 5-8 after DOC withdrawal showed marginal blood pressure elevation, whereas eplerenone alone or coadministered with RU486 reversed all DOC/salt-induced circulatory and cardiac pathology. Thus, sustained responses after mineralocorticoid withdrawal appear to be independent of GR signaling, in that blockade of endogenous antiinflammatory effects via GR does not lead to an increase in the severity of responses in the mineralocorticoid/salt-treated rat after steroid withdrawal.

Acute effects of neurosteroids in a rodent model of primary paroxysmal dystonia

The pathophysiology of various types of dyskinesias, including dystonias, is poorly understood. Clinical and epidemiological studies in humans revealed that the severity of dyskinesias and the frequency of paroxysmal forms of the disease are altered by factors such as the onset of puberty, pregnancy, cyclical changes and stress, indicating an underlying hormonal component. The dystonic phenotype in the dt(sz) hamster, a genetic animal model of paroxysmal dystonia, has been suggested to be based on a deficit of striatal gamma-aminobutyric acid (GABA)ergic interneurons and changes in the GABA(A) receptor complex. In this animal model, hormonal influences seem to be also involved in the pathophysiology, but an influence of peripheral sex hormones has already been excluded. Possibly, neurosteroids as endogenous regulators of the GABA(A) receptor may be critically involved in the pathophysiology of dystonia in this animal model. Therefore, in the present study, the effects of the neurosteroids allopregnanolone acetate and allotetrahydrodeoxycorticosterone (THDOC), representing positive modulators of the GABA(A) receptor, as well as of the negative GABA(A) receptor modulators pregnenolone sulfate and dehydroepiandrosterone (DHEA), on severity of dystonia were examined in dt(sz) hamsters after acute intraperitoneal injections. Allopregnanolone acetate and THDOC exerted a moderate reduction of dystonia, whereas pregnenolone sulfate and DHEA had no significant effects. Although the effects of allopregnanolone acetate and THDOC were moderate and short-lasting, the present results suggest that changes in neurosteroid levels might be involved in the initiation of dystonic episodes. Future studies have to include measurements of brain neurosteroid levels as well as of chronic neurosteroid administrations to clarify the pathophysiological role and therapeutic potential of neurosteroids in dystonia.

Involvement of the endothelin ET(B) receptor in gender differences in deoxycorticosterone acetate-salt-induced hypertension

1. In the present study, we investigated the role of endothelin ET(B) receptors in gender differences in the development of deoxycorticosterone acetate (DOCA)-salt-induced hypertension by using the spotting-lethal (sl) rat, which carries a naturally occurring deletion in the ET(B) receptor gene. 2. In wild-type rats, the elevation of systolic blood pressure (SBP) by DOCA-salt treatment for 4 weeks was extremely lower in females than in males, but this gender difference was partially attenuated in ovariectomized (OVX) animals. These alterations of SBP corresponded with vascular superoxide () production. 3. In homozygous (sl/sl) group, the SBP of male, intact female and OVX rats was markedly elevated by DOCA-salt treatment to the same extent, indicating that the gender difference in DOCA-salt-induced hypertension was abolished by the genetic ET(B) receptor deficiency. There were similar increases in the vascular endothelin (ET)-1 content in the three DOCA-salt-treated animal groups, but vascular production in male and OVX rats was much higher than that in intact females. 4. Daily oral administration of ABT-627, an ET(A) receptor antagonist, to sl/sl rats for 2 weeks suppressed the DOCA-salt-induced hypertension more efficiently in intact female rats than in male animals. 5. Thus, vascular oxidative stress is related, at least in part, to differences in the development of DOCA-salt-induced hypertension between male and female rats, but this gender difference is abolished by the genetic ET(B) receptor deficiency, suggesting that ET(B) receptor-mediated vasoprotective actions contribute to the gender differences seen. In addition, in both sexes, vascular ET-1 overproduction and the ET(A) receptor-mediated action seem to be responsible for the enhanced susceptibility to DOCA-salt hypertension in genetic ET(B) receptor deficiency.

Time course of synergistic interaction between DOCA and salt on blood pressure: roles of vasopressin and hepatic osmoreceptors

In DOCA-salt rats, the time course of the synergistic interaction between osmolality and DOCA to produce hypertension is unknown. Therefore, in rats 2 wk after implantation of subcutaneous silicone pellets containing DOCA (65 mg) or no drug (sham), we determined blood pressure (BP) and heart rate (HR) responses, using telemetric pressure transducers, during 2 wk of excess salt ingestion (1% NaCl in drinking water). BP was unaltered in sham rats after increased salt, but in DOCA rats BP increased within 4 h. The initial hypertension of 30–35 mmHg stabilized within 2 days, followed ∼5 days later by a further increment of ∼30 mmHg. HR first decreased during the dark phase; the second phase was linked to an abrupt increase in HR and BP variability and decreased HR variability. Pressor responses to acute intravenous hypertonic saline infusion were doubled in DOCA-treated rats via vasopressin and nonvasopressin mechanisms. Only in DOCA-treated rats, portal vein hypertonic saline infusion increased BP, which was prevented by V1 vasopressin blockade. After 2 wk of DOCA-salt, oral ingestion of water rapidly decreased BP. Intraportal infusion of water did not lower BP in DOCA-salt rats, suggesting that hepatic osmoreceptors were not involved. In summary, the hypertension of DOCA-treated rats consuming excess salt exhibits multiple phases and can be rapidly reversed. Hypertonicity-induced vasopressin and nonvasopressin pressor mechanisms that are augmented by DOCA, and hepatic osmoreceptors may contribute to the initial developmental phase. With time, combined DOCA-salt induces marked changes in the regulation of the autonomic nervous system, which may favor hypertension development.

Role of gp91phox-containing NADPH oxidase in the deoxycorticosterone acetate-salt-induced hypertension

NADPH oxidase plays an important role in vascular oxidative stress in hypertensive diseases. We evaluated whether NADPH oxidase-dependent superoxide (O(2)(-)) production is involved in the deoxycorticosterone acetate (DOCA)-salt-induced hypertension, using mice which are genetically deficient in gp91phox, an NADPH oxidase subunit protein (gp91(-/-) mice). Two weeks after the DOCA-salt treatment, systolic blood pressure was significantly elevated in wild-type mice, but not in gp91(-/-) mice. After a 5-week treatment period, wild-type mice developed high blood pressure, with a systolic blood pressure of 127 +/- 3 mm Hg, compared with 107 +/- 4 mm Hg in gp91(-/-) mice. Aortic O(2)(-) production in wild-type DOCA-salt-treated mice was significantly higher than that in wild-type sham mice, whereas there were no significant differences in aortic O(2)(-) production between gp91(-/-) DOCA-salt-treated and sham mice. These findings suggest that vascular O(2)(-) overproduction via gp91phox-containing NADPH oxidase is one of the crucial factors in the development of DOCA-salt-induced hypertension.

Down-regulation of adrenal neuronal nitric oxide synthase mRNAs and proteins after deoxycorticosterone acetate-salt treatment in rats

The aim of this study was to evaluate the possible changes of adrenal neuronal nitrite oxide synthase (nNOS) messenger RNA (mRNA) and protein of rats after deoxycorticosterone acetate (DOCA)-salt treatment. We determined adrenal nNOS expression in 12 vehicle-treated and 13 DOCA-salt-treated rats by in situ hybridization, immunohistochemistry, and multiplex RT-PCR methods. Adrenal nNOS was also detected by Western blot in five vehicle-treated and five DOCA-salt-treated rats. The results showed that adrenal nNOS mRNA and nNOS immunoreactivities were mainly localized in the medulla and some in the regions of zona glomerulosa. DOCA-salt treatment inactivated nNOS mRNA and peptide expression prominent in the adrenal medulla and slight in the zona glomerulosa. The relative quantities of nNOS mRNA in the adrenals of the DOCA-salt-treated group was 8.8-fold decreased. At the same time, the relative quantities of steroid acute regulatory protein mRNA and phenylethanolamine N-methyltransferase mRNA in the adrenals of the DOCA-salt-treated group were significantly decreased. Western blots showed that total adrenal nNOS were 3.7-fold down-regulated after DOCA-salt treatment. Our results indicated that the down-regulation of adrenal nNOS synthesis might be associated with the inactivation of adrenal function in face of volume expansion.

In the ventral tegmental area, progestins have actions at D1 receptors for lordosis of hamsters and rats that involve GABA A receptors

In the ventral tegmental area (VTA), progestins facilitate lordosis via actions at gamma-aminobutyric acid (GABA)(A)/benzodiazepine receptor complexes (GBRs) and dopamine type 1 receptors (D1). The relationship between progestins' actions at GBRs and D1 in the VTA for facilitating sexual behavior of hamsters and rats was examined. Ovariectomized (ovx), estradiol (E(2); 10 microg)+progesterone (P; 250 microg; SC)-primed hamsters, with bilateral guide cannulae to the VTA, were pre-tested for sexual and motor behavior and infused with the GBR antagonist bicuculline (100 ng/side) or vehicle. Thirty minutes later, hamsters were re-tested and then infused with the D1 agonist SKF38393 (100 ng/side) or vehicle. Hamsters were post-tested 30 min later. Ovx, E(2) (10 microg)-primed rats were pre-tested, infused first with bicuculline or vehicle, second with SKF38393 or vehicle, third with 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP; 0, 100, or 200 ng) and were post-tested 10 and 60 min after 3alpha,5alpha-THP infusions. VTA infusions of SKF38393 increased lordosis of hamsters or rats. Bicuculline pretreatment reduced SKF38393- and/or progesterone-mediated increases in lordosis of E2-primed hamsters. In E2-primed rats, bicuculline blocked SKF38393- and/or 3alpha,5alpha-THP-mediated increases in lordosis. There were no effects on motor behavior. Thus, in the VTA, GBR activity modulates D1-mediated actions for lordosis of hamsters and rats.

Epidermal growth factor induces vasoconstriction through the phosphatidylinositol 3-kinase-mediated mitogen-activated protein kinase pathway in hypertensive rats

We investigated whether increased contractile responsiveness to epidermal growth factor (EGF) is associated with altered activation of mitogen-activated protein kinase (MAPK) in the aortic smooth muscle of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. EGF induced contraction and MAPK activity in aortic smooth muscle strips, which were significantly increased in tissues from the DOCA-salt hypertensive rats compared with those from sham-operated rats. AG1478, PD98059, and LY294002, inhibitors of EGF receptor (EGFR) tyrosine kinase, MAPK/extracellular signal-regulated kinase (ERK) kinase, and phosphatidylinositol 3-kinase (PI3K), respectively, inhibited the contraction and the activity of ERK1/2 that were elevated by EGF. Y27632 and GF109203X, inhibitors of Rho kinase and protein kinase C, respectively, attenuated EGF-induced contraction, with no diminution of ERK1/2 activity. Although EGF also elevated the activity of EGFR tyrosine kinase in both sham-operated and DOCA-salt hypertensive rats, the expression and the magnitude of activation did not differ between strips. These results strongly suggest that EGF induces contraction by the activation of ERK1/2, which is regulated by the PI3K pathway in the aortic smooth muscle of DOCA-salt hypertensive rats.

Blood pressure variability, cardiac baroreflex sensitivity and organ damage in experimentally hypertensive rats

1. The present study was designed to investigate the haemodynamic features and morphological changes in experimentally hypertensive rat models. 2. Sprague-Dawley rats were used to prepare the experimentally hypertensive models, including two-kidney, one-clip renovascular hypertensive (2K1C) rats, deoxycorticosterone acetate salt hypertensive (DOCA) rats and N(G)-nitro-l-arginine methyl ester-induced hypertensive (l-NAME) rats. Six weeks after the induction of hypertension, 24 h blood pressure was recorded and blood pressure variability (BPV) expressed by 24 h (or 12 h in the daytime and night-time study) standard deviation of the variables was calculated. Then, cardiac baroreflex sensitivity (BRS) was determined and four endogenous factors (tumour necrosis factor-alpha, interleukin-1beta, angiotensin II and endothelin-1) were measured. Finally, morphological changes were examined. 3. It was found that an increase in BPV and a decrease in BRS were accompanied by an elevation of blood pressure in all three hypertensive models. The DOCA rats had the highest BPV, whereas the l-NAME rats had the lowest BRS. 4. Morphological changes were similar in DOCA and l-NAME rats and the cardiac changes were relatively slight in 2K1C rats. Tumour necrosis factor-alpha was increased in all the three models, especially in DOCA rats. Endothelin-1 was higher in DOCA rats and angiotensin II was increased in 2K1C rats and decreased in DOCA rats. 5. In conclusion, increased BPV and decreased BRS accompanied the elevation of blood pressure in all three hypertensive models. The DOCA rats had the highest BPV and the l-NAME rats had the lowest BRS. Obvious organ damage was seen in all three hypertensive models 6 weeks after the induction of hypertension.

The effect of hypertension on serum nitric oxide and vascular endothelial growth factor concentrations. A study in DOCA-Salt hypertensive ovariectomized rats

CardioVascular Disease (CVD) accounts for considerable mortality and morbidity in developed countries. Most of the common forms of CVD, such as hypertension, are caused by functional and structural changes in endothelial function. This study was designed to study the effect of hypertension on serum Nitric Oxide (NO) and Vascular Endothelial Growth Factor (VEGF) concentrations in DOCA-Salt hypertensive ovariectomized rats. Thirty female rats were ovariectomized. Blood samples were taken and the animals were divided into hypertensive and control groups. Hypertension was induced by DOCA-Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the experiment. The control group received normal saline injection with usual drinking water. Results showed that serum NO concentration in DOCA-Salt hypertensive rats was lower than the control group (18.35 +/- 5.31, 45.01 +/- 12.54 micromol/l, respectively) (p < 0.05). Also, the mean serum VEGF concentration was raised after induced hypertension (120.55 +/- 8.11 vs. 88.58 +/- 2.24 pg/ml) (p < 0.05). In conclusion, reduced serum NO and increased serum VEGF concentrations in hypertensive animals support the concept of endothelial dysfunction in hypertensive subjects.

Mid-aged and aged wild-type and progestin receptor knockout (PRKO) mice demonstrate rapid progesterone and 3alpha,5alpha-THP-facilitated lordosis

RATIONALE

Progesterone (P) and its 5alpha-reduced metabolite, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP), facilitate sexual behavior of rodents via agonist-like actions at intracellular progestin receptors (PRs) and membrane GABA(A)/benzodiazepine receptor complexes (GBRs), respectively.

OBJECTIVE

Given that ovarian secretion of progestins declines with aging, whether or not senescent mice are responsive to progestins was of interest.

METHODS

Homozygous PR knockout (PRKO) or wild-type mice that were between 10-12 (mid-aged) or 20-24 (aged) months of age were administered P or 3alpha,5alpha-THP, and the effect on lordosis were examined. Effects of a progestin-priming regimen that enhances PR-mediated (experiment 1) or more rapid, PR-independent effects of progestins (experiments 2 and 3) on sexual behavior were examined. Levels of P, 3alpha,5alpha-THP, and muscimol binding were examined in tissues from aged mice (experiment 4).

RESULTS

Wild-type, but not PRKO, mice were responsive when primed with 17beta-estradiol (E(2); 0.5 microg) and administered P (500 microg, subcutaneously). Mid-aged wild-type mice demonstrated greater increases in lordosis 6 h later compared to their pre-P, baseline test than did aged wild-type mice (experiment 1). Lordosis of younger and older wild-type, but not PRKO, mice was significantly increased within 5 min of intravenous (IV) administration of P (100 ng), compared with E(2)-priming alone (experiment 2). However, wild-type and PRKO mice demonstrated significant increases in lordosis 5 min after IV administration of 3alpha,5alpha-THP, an effect which was more pronounced in mid-aged than in aged animals (100 ng-experiment 3). In tissues from aged wild-type and PRKO mice, levels of P, 3alpha,5alpha-THP, and muscimol binding were increased by P administration (experiment 4). PR binding was lower in the cortex of PRKO than that of wild-type mice.

CONCLUSIONS

Mid-aged and aged PRKO and wild-type mice demonstrated rapid P or 3alpha,5alpha-THP-facilitated lordosis that may be, in part, independent of activity at PRs.

Detection of serum autoantibodies against AT₁A-receptor during the development of the four types of hypertensive rat models

Using two-kidney one-clip renal hypertensive (2K1C group), stress-induced hypertensive (neural group), DOCA-salt treated hypertensive (DOCA group) and spontaneously hypertensive rats (SHR group), to investigate the change in AT(1A)-receptor autoantibodies (AT(1A)-AAs) during the development of the four types of hypertension. The biological activities of AT(1A)-AAs were examined. It was shown that the frequency of occurrence and titres of AT(1A)-AAs increased significantly during the development of hypertension. In the four hypertensive groups studied, the occurrence of AT(1A)-AAs was most prominent in SHR, 2K1C and neural groups. The biological effects of AT(1A)-AAs were shown to increase the beating frequency of cultured neonatal myocardial and vascular contractile tension. It is suggested that autoimmune mechanisms are involved the pathogenesis of different types of hypertension and the AT(1A)-AAs may be one of the mechanisms leading to cardiac hypertrophy.

Exaggerated liver injury induced by ischemia-reperfusion in spontaneously hypertensive rats

BACKGROUND

The functions of polymorphonuclear leukocytes (PMNs), which play a critical role in organ damage, are primed in patients with essential hypertension and spontaneously hypertensive rats (SHR). Hepatic ischemia-reperfusion (I/R) injury is shown to be caused and aggravated by the PMNs. We examined whether the hepatic I/R injury was exaggerated in SHR.

METHODS

The portal vein and artery were partially occluded for 60 min. Blood samples were obtained to determine the degree of liver damage during 48 h after reperfusion.

RESULTS

The increase in serum transaminase concentration and hepatic myeloperoxidase content, which reflects the number of PMNs in liver tissue, in SHR were significantly greater than those of their control rats, Wistar-Kyoto rat (WKY). However, the elevations in hepatic transaminases induced by I/R did not differ between other hypertensive animal models (N-nitro-L-arginine methyl ester [L-NAME]-treated and deoxycorticosterone acetate [DOCA]/salt-treated rats) and their controls.

CONCLUSIONS

These results suggest that the elevated PMNs, but not high blood pressure per se, contributes to the exaggerated hepatic I/R injury in SHR.

Endothelial progenitor cell senescence is accelerated in both experimental hypertensive rats and patients with essential hypertension

OBJECTIVES

Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cells (EPCs). Although hypertension is an important coronary risk factor, the influence to the EPCs is not fully understood. We investigated the effect of hypertension on EPC senescence.

METHODS

Experimental study We investigated the number and senescence of EPCs in spontaneously hypertensive rats (SHR/Izm) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. EPCs were isolated from peripheral blood of rats and were characterized. EPC senescence was detected by acidic beta-galactosidase staining. In addition, we measured the telomerase activity using polymerase chain reaction-enzyme-linked immunosorbent assay.

CLINICAL STUDY

EPCs were isolated from peripheral blood samples in 37 patients with essential hypertension. After ex-vivo cultivation, we detected senescence and measured the telomerase activity. The total severity index of hypertension-induced organ damage was calculated by the summation of each severity index in the classification of hypertension severity by Tokyo University (1984).

RESULTS

Experimental study The EPC senescence in SHR/Izm and DOCA-salt hypertensive rats was significantly increased compared with that of control rats. The telomerase activities in SHR/Izm and DOCA-salt hypertensive sensitive rats were also significantly lowered compared with those of control rats. Clinical study Compared with the control group, EPCs from hypertensive patients showed accelerated senescence and also showed reduced telomerase activity. In hypertensive patients, the degree of hypertension-induced organ damage was negatively correlated with telomerase activity, and was positively correlated with EPC senescence.

CONCLUSIONS

EPC senescence is accelerated in both experimental hypertensive rats and patients with essential hypertension, which may be related to telomerase inactivation. The hypertension-induced EPC senescence may affect the process of vascular remodeling.

Involvement of marinobufagenin in a rat model of human preeclampsia

BACKGROUND

Preeclampsia is a potentially devastating disorder of hypertension in pregnancy for which there is currently no definitive treatment short of delivery. The bufadienolide, marinobufagenin (MBG), an inhibitor of Na(+)/K(+) ATPase, has been found to be elevated in extracellular fluid volume-expanded hypertensive patients, a condition similar to preeclampsia. Thus, these studies sought to examine the role of MBG in our rat model of preeclampsia.

METHODS AND RESULTS

Pregnant female rats were injected intraperitoneally with deoxycorticosterone acetate (DOCA) and given 0.9% saline as drinking water for the duration of their pregnancy. Urinary MBG was measured using a DELFIA immunoassay. Blood pressure was measured via the tail-cuff method. Injections of anti-MBG antibody were given intraperitoneally or intravenously to hypertensive pregnant rats. MBG was given intraperitoneally to pregnant rats. Uterine arterioles were dissected free and their diameters were measured before and after perfusion of MBG, ouabain, or digoxin. MBG was found to be elevated in the pregnant + DOCA + saline (PDS) rats compared to normal pregnant animals. In addition, when PDS rats were injected with anti-MBG antibody, there was a subsequent reduction in blood pressure. Administration of MBG in normal pregnant rats caused an elevation in blood pressure equivalent to the PDS model. Also, uterine vessel measurements showed an increased vasoconstrictive reactivity to MBG in the PDS animals vs. the normal pregnant controls; while no changes were observed with perfusion of digoxin or ouabain at the same concentration.

CONCLUSION

These results suggest a relationship between MBG and a syndrome in rats resembling preeclampsia. Armed with these promising results, it would seem logical to further examine the role of MBG in human preeclampsia.

Chronic treatment with mianserin prevents DOCA–salt hypertension in rats—evidence for the involvement of central 5-HT2 receptors

Central 5-HT2A receptors have been implicated in central volume control by activating a central angiotensinergic pathway to cause the release of vasopressin. Interestingly, to induce DOCA-salt hypertension in rats vasopressin release is required. Thus the present experiments were carried out to determine whether continuous blockade of these receptors over 20 days, with the non-selective 5-HT2 receptor antagonist mianserin would prevent the development of deoxycorticosterone acetate (DOCA)-salt hypertension. Mianserin, given i.c.v. 90 or 60 microg twice daily for 20 days prevented the development of hypertension in conscious rats receiving DOCA-salt but did not affect blood pressure in rats on salt alone. Further, the dose of 30 microg given i.c.v. twice daily had no effect nor did the vehicle, polyethylene glycol (PEG), on the development of the hypertension. Mianserin 90 microg twice daily i.c.v. was also shown to prevent the increase in fluid intake, urinary flow and sodium excretion caused by DOCA-salt treatment. These data indicate that this action of mianserin is not due to an intrinsic hypotensive action but an action which involves interference with the mechanism by which DOCA-salt treatment causes hypertension. Thus the data overall support the view that to induce hypertension with DOCA-salt a central 5-HT-containing pathway needs to be activated, which then activates 5-HT2 receptors to cause the release of vasopressin which has previously been shown to be responsible for the initiation of DOCA-salt treatment hypertension.

Plasma concentrations of anxiolytic neuroactive steroids in men with panic disorder

Plasma concentrations of neuroactive steroids in men with panic disorder (PD) were measured to evaluate their relations to psychopathology both before and during treatment. Participants comprised 13 men with PD and 10 normal controls. Patients were evaluated while drug-free as well as after 1 and 2 months of paroxetine therapy. Psychopathology was assessed by the State-Trait Anxiety Inventory (STAI), the Panic-Associated Symptom Scale, and the Fear Questionnaire total score. Plasma concentrations of steroids were measured by radioimmunoassay. The plasma concentrations of progesterone and dehydroepiandrosterone were greater in drug-free patients than in controls, whereas those of allopregnanolone and tetrahydrodeoxycorticosterone did not differ between the two groups. Paroxetine treatment for 2 months significantly increased the plasma concentration of allopregnanolone but did not affect those of the other steroids. At 2 months of therapy, allopregnanolone concentrations in patients were significantly greater than those in controls. The plasma concentrations of progesterone and tetrahydrodeoxycorticosterone correlated with the STAI state score in patients before treatment. Our data suggest that neuroactive steroids may play a role in PD in men.

Mitogen-activated protein kinase contributes to elevated basal tone in aortic smooth muscle from hypertensive rats

The role of mitogen-activated protein kinase (MAPK) in increased basal tone -spontaneous resistance in vascular muscle strips- was clarified in aortic smooth muscle from deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The MAPK/extracellular signal-regulated protein kinase (ERK) kinase inhibitor, PD098059 (2'-amino-3'-methoxyflavone), significantly inhibited basal tone in a dose-dependent manner. The basal level of ERK1/2 activation was inhibited by PD098059 and was significantly greater in hypertensive rats than in sham-operated rats. In contrast, inhibition with PD098059 was not observed in sham-operated rats. GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)maleimide), an inhibitor of protein kinase C (PKC), decreased both basal tone and ERK1/2 activity in the hypertensive rats. In contrast, Y27632 ((R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide) and verapamil, inhibitors of Rho kinase and voltage-dependent Ca2+ channels, respectively, significantly inhibited basal tone but not ERK1/2 activity. Thus, basal vascular tone is elevated by the altered activation of MAPK in DOCA-salt hypertensive rats, and this is regulated by PKC, but not by Rho or intracellular Ca2+.

Identification of hypertension-related genes through an integrated genomic-transcriptomic approach

In search for the genetic basis of hypertension, we applied an integrated genomic-transcriptomic approach to identify genes involved in the pathogenesis of hypertension in the Sabra rat model of salt-susceptibility. In the genomic arm of the project, we previously detected in male rats two salt-susceptibility QTLs on chromosome 1, SS1a (D1Mgh2-D1Mit11; span 43.1 cM) and SS1b (D1Mit11-D1Mit4; span 18 cM). In the transcriptomic arm, we studied differential gene expression in kidneys of SBH/y and SBN/y rats that had been fed regular diet or salt-loaded. We used the Affymetrix Rat Genome RAE230 GeneChip and probed >30,000 transcripts. The research algorithm called for an initial genome-wide screen for differentially expressed transcripts between the study groups. This step was followed by cluster analysis based on 2x2 ANOVA to identify transcripts that were of relevance specifically to salt-sensitivity and hypertension and to salt-resistance. The two arms of the project were integrated by identifying those differentially expressed transcripts that showed an allele-specific hypertensive effect on salt-loading and that mapped within the defined boundaries of the salt-susceptibility QTLs on chromosome 1. The differentially expressed transcripts were confirmed by RT-PCR. Of the 2933 genes annotated to rat chromosome 1, 1102 genes were identified within the boundaries of the two blood pressure QTLs. The microarray identified 2470 transcripts that were differentially expressed between the study groups. Cluster analysis identified genome-wide 192 genes that were relevant to salt-susceptibility and/or hypertension, 19 of which mapped to chromosome 1. Eight of these genes mapped within the boundaries of QTLs SS1a and SS1b. RT-PCR confirmed 7 genes, leaving TcTex1, Myadm, Lisch7, Axl-like, Fah, PRC1-like, and Serpinh1. None of these genes has been implicated in hypertension before. These genes become henceforth targets for our continuing search for the genetic basis of hypertension.

Nitric oxide synthase expression in AT2 receptor-deficient mice after DOCA-salt

BACKGROUND

Angiotensin II type 2 receptor-deficient mice (AT(2)-/y) provide an opportunity to study the relationship between the angiotensin II type 1 receptor (AT(1)) and nitric oxide synthase (NOS) isoforms without concomitant AT(2) receptor-related effects. To test this relationship, the expression of renal NOS isoforms (neural, inducible, and endothelial) in AT(2)-/y and AT(2)+/y mice was examined. The mice were challenged with deoxycorticosterone acetate (DOCA)-salt to stimulate NO generation.

METHODS

Gene expression analyses by real-time polymerase chain reaction (PCR) (TaqMan) were performed in kidneys to characterize neuronal nitric oxide synthase (nNOS), epithelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and the AT(1) receptor. Pressure-natriuresis experiments were done to determine the physiologic background.

RESULTS

AT(2)-/y mice showed nNOS and iNOS up-regulation. DOCA-salt increased iNOS expression more in AT(2)-/y mice than in AT(2)+/y mice. Immunohistochemistry localized the iNOS expression with DOCA-salt mainly in the glomeruli. eNOS was not different between the groups, and was not affected by DOCA-salt. DOCA-salt increased mean arterial pressure more in AT(2)-/y mice than in AT(2)+/y mice. Concomitantly, the pressure-natriuresis relationship was shifted to the right in AT(2)-/y and AT(2)+/y mice after DOCA-salt. DOCA-salt decreased renal blood flow (RBF) and glomerular filtration rate (GFR) in both groups. iNOS blockade did not lower blood pressure.

CONCLUSION

We conclude that AT(2) receptor deletion and concomitant up-regulation of the AT(1) receptor is associated with up-regulation of nNOS and iNOS. Under DOCA-salt, renal iNOS expression was further increased. Because iNOS inhibition did not change blood pressure, iNOS may not be involved in the hemodynamics, but may contribute to organ damage.

Effects of chronic quercetin treatment on antioxidant defence system and oxidative status of deoxycorticosterone acetate-salt-hypertensive rats

We investigated the potential of chronic administration of an oral daily dose (10 mg/kg) of the dietary flavonoid quercetin to prevent hypertension and oxidative stress induced by deoxycorticosterone acetate (DOCA)-salt in rats. We have compared its effects to those produced by the well-known anti-hypertensive drug verapamil, administered orally (20 mg/kg/day). Quercetin and verapamil treatments reduced systolic blood pressure of DOCA-salt rats in approximately 67.6 and 63.3% respectively, producing no effect in control animals. Both drugs reduced significantly hepatic and renal hypertrophy induced by DOCA-salt administration, while only quercetin prevented cardiac hypertrophy. Decreased endothelium-dependent relaxation to acetylcholine of aortic rings from DOCA-salt-treated rats was improved by quercetin, but verapamil only enhanced it in the presence of superoxide dismutase (SOD) plus catalase. Increased plasma and heart thiobarbituric acid reactive substances (TBARS) and total glutathione (GSH) levels in liver and heart, decreased liver glutathione peroxidase (GPX) and liver and kidney glutathione transferase (GST) activities were observed in DOCA-salt-treated rats compared to the control animals. The antihypertensive effect of quercetin was accompanied by normalisation of plasma TBARS values, improvement of the antioxidant defences system in heart and liver, restoring total GSH levels in both organs and altered liver GST and GPX activities, and improving kidney GST activity. Verapamil treatment only restored GSH levels in heart, having no effect on other alterations induced by DOCA-salt chronic administration in the antioxidant defences analysed. In conclusion, quercetin shows both antihypertensive and antioxidant properties in this model of mineralocorticoid hypertension, while verapamil exhibits only antihypertensive effects.

Effects of deoxycorticosterone on renal vascular reactivity and flow-pressure curve in spontaneously hypertensive rats

The role of mineralocorticoids as sodium retaining hormones has been recently enlarged to include their function as modulators of cardiovascular function and injury. This study evaluated the contribution of possible functional changes in resistance vessels to the additional BP increase produced by the chronic administration of DOCA to SHR. The flow-pressure curve and renal responses to vasoconstrictors (phenylephrine [Phe] and angiotensin II [AII]) and vasodilators (acetylcholine [ACh] and nitroprusside [NP]) were characterized in isolated kidneys from Wistar Kyoto (WKY) and SHR treated or untreated with DOCA for nine weeks. DOCA increased BP in SHR but did not modify BP in WKY rats. Kidneys from SHR showed enhanced reactivity to Phe and AII that was not increased by DOCA. DOCA reduced sensitivity to AII in SHR. Responsiveness to ACh was increased in SHR and was not attenuated by DOCA in WKY or SHR. Vasodilator response to NP was not significantly affected by DOCA in WKY or SHR. The flow-pressure curve was markedly up-shifted in SHR when compared with kidneys from WKY rats. DOCA administration did not modify the flow-pressure curve in WKY but produced attenuation at low flow levels in SHR. Our results demonstrate that DOCA increases BP in SHR but does not increase the flow-pressure curve or renal vascular reactivity to vasoconstrictors, and does not reduce responsiveness to endothelium-dependent and independent vasodilators in SHR or WKY rats. Therefore, our data suggest that the BP increase produced by DOCA in SHR is not related to abnormalities in vascular function in resistance vessels.

The role of chloride in deoxycorticosterone hypertension: selective sodium loading by diet or drinking fluid

To evaluate the role of chloride in the pathogenesis of salt-dependent deoxycorticosterone (DOC) hypertension, we studied young Wistar rats chronically loaded with sodium bicarbonate (NaHCO(3)) or sodium chloride (NaCl) which were administered either in the diet or in the drinking fluid. Selective sodium loading (without chloride) increased blood pressure (BP) in DOC-treated animals only if NaHCO(3) was provided in the diet. In contrast, no significant blood pressure changes were induced by DOC treatment in rats drinking NaHCO(3) solution. Hypernatremia and high plasma osmolality occurred only in rats drinking NaCl or NaHCO(3) solutions. Compared to great volume expansion in NaCl-loaded DOC-treated rats, the degree of extracellular fluid volume expansion (namely of its interstitial fraction) was substantially lower in both NaHCO(3)-loaded groups in which significant hypokalemia was observed. NaHCO(3)-drinking rats without significant blood pressure response to DOC treatment represented the only experimental group in which blood volume was not expanded. In conclusion, our data confirm previous observations that NaHCO(3) loading is less potent in eliciting DOC hypertension than NaCl loading, but blood pressure rise in rats fed NaHCO(3) diet clearly demonstrated that selective sodium loading could potentiate the development of DOC hypertension if NaHCO(3) is offered within the appropriate dietary regimen. The reasons for the failure of NaHCO(3)-drinking rats to elevate blood pressure in response to chronic mineralocorticoid treatment are not obvious. However, the absence of a significant plasma volume expansion together with hypernatremia and increased plasma osmolality suggest a considerable degree of dehydration in these animals which fail to increase their fluid consumption compared to water drinking rats.

Nephroprotective effects of the endothelin ET(A) receptor antagonist darusentan in salt-sensitive genetic hypertension

We tested the effect of selective endothelin ET(A) receptor blockade on the development renal damage in the Sabra rat model of genetic salt-sensitivity. Animals from the salt-sensitive (SBH/y) and salt-resistant strains (SBN/y) were either salt-loaded with deoxycorticosterone acetate and salt (DOCA) or fed a normal diet. Additional salt-loaded groups were also treated with the selective ET(A) antagonist darusentan (DA). Salt-loading in SBH/y increased systolic blood pressure by 75 mm Hg and urinary albumin excretion 23-fold (P<0.0001). Darusentan attenuated the rise of systolic blood pressure (50%) and urinary albumin excretion (63%, P<0.01, respectively). Salt-loading in SBH/y was associated with significant increased osteopontin mRNA expression as well as glomerulosclerosis and tubulointerstitial damage in the kidney (P<0.05, respectively). This was either significantly reduced or normalized by darusentan (P<0.05, respectively). Thus, darusentan confers a significant renal protection in the Sabra model of salt-sensitive hypertension.

Analysis of differential gene expression in stretched podocytes: osteopontin enhances adaptation of podocytes to mechanical stress

Glomerular hypertension is a major determinant advancing progression to end-stage renal failure. Podocytes, which are thought to counteract pressure-mediated capillary expansion, are increasingly challenged in glomerular hypertension. Studies in animal models of glomerular hypertension indicate that glomerulosclerosis develops from adhesions of the glomerular tuft to Bowman's capsule due to progressive podocyte loss. However, the molecular alterations of podocytes in glomerular hypertension are unknown. In this study, we determined the changes in gene expression in podocytes induced by mechanical stress in vitro (cyclic biaxial stretch, 0.5 Hz, 5% linear strain, 3 days) using cDNA arrays (6144 clones). Sixteen differentially regulated genes were identified, suggesting alterations of cell-matrix interaction, mitochondrial/metabolic function, and protein synthesis/degradation in stretched podocytes. The transcript for the matricellular protein osteopontin (OPN) was most strongly up-regulated by stretch (approximately threefold). By reverse transcriptase-polymer chain reaction, up-regulation of OPN mRNA was also detected in glomeruli of rats treated for 2.5 wk with desoxycorticosterone acetate-salt, an animal model of glomerular hypertension. In cultured podocytes, OPN coating induced a motile phenotype increasing actin nucleation proteins at cell margins and reducing stress fibers and focal adhesions. Intriguingly, additional OPN coating of collagen IV-coated membranes accelerated stretch-induced actin reorganization and markedly diminished podocyte loss at higher strain. This study delineates the molecular response of podocytes to mechanical stress and identifies OPN as a stretch-adapting molecule in podocytes.

Dose-, time-, age-, and sex-response profiles for the anticonvulsant effects of deoxycorticosterone in 15-day-old rats

Recently, we have shown that a single high dose of the adrenal steroid precursor hormone deoxycorticosterone (DOC) has potent anticonvulsant effects in 15-day-old rats. To better define the actions of DOC, the present study established dose-, time-, age-, and sex-response curves for the anticonvulsant actions of DOC. Methods. Dose- and time-response studies were done using two different seizure models: (1) maximal pentylenetetrazol seizures (MMT) and (2) maximal electroconvulsive shock (MES) seizures. Subsequently, age- and sex-response studies were done using MMT seizures and two different DOC doses, one low (nonsedating) and one high (sedating). Results. In dose-response studies, DOC suppressed MMT seizures with an ED(50) of about 5 mg/kg (sc). Higher doses were necessary to suppress MES seizures, where the ED(50) was about 20 mg/kg. In time-response studies, DOC's effects were rapid in onset. Complete suppression of seizures was seen by 5 min in the MES model and by 15 min in the MMT model. In developmental studies, both a low nonsedating and a high sedating dose of DOC suppressed MMT seizures in neonatal, infant, weanling, and juvenile rats of either sex. The suppressive effects of low-dose DOC were lost after puberty, however. The suppressive effects of high-dose DOC also declined after puberty, especially in males. Conclusion. DOC has significant anticonvulsant actions that occur in prepubertal, but not postpubertal subjects. DOC might have clinical importance in the future treatment of childhood seizure disorders.

[Immunomodulation after keratoplasty by CTL4-Ig and anti-CD154 antibodies]

BACKGROUND

The immunoreaction after corneal transplantation is caused by the T cell receptor interacting with the major histocompatibility complex (MHC) receptor of the antigen-presenting cell. The signal is amplified by the CD4 receptor and the costimulatory signal interactions of CD28-B7 and CD40-CD154. We investigated the influence of costimulatory signal blocking on corneal transplant survival in mice.

METHODS

Seven groups of 6 BALB/c mice received an orthotopic corneal transplant from C3H mice differing in minor and major MHC and were postoperatively treated as follows: (1) 80 micrograms of CTLA4 fusion protein intraperitoneally (i.p.) for 6 days; (2) 50 microliters of PBS i.p. for 6 days; (3) 1 mg of Solu-Decortin H i.p. for 5 days + dexamethasone AT 0.1% for 35 days; (4) therapy (3) + 50 micrograms of CTLA4 fusion protein i.p. for 6 days; (5) CTLA4-Ig as in (1) + 15 micrograms of anti-CD154 subconjunctivally (s.c.) on days 0, 2, 4, 6, and 8; (6) CTLA4-Ig as in (1) + 25 micrograms of anti-CD154 s.c. for 9 days; and (7) 25 microliters of PBS s.c. for 9 days.

RESULTS

All animals had an immunoreaction on the following days: (1) day 18 +/- 3.1; (2) day 13.6 +/- 1.6; (3) day 48 +/- 6.6; (4) day 65 +/- 41; (5) day 23.5 +/- 8.5; (6) day 16.2 +/- 3.6; (7) day 13.8 +/- 2.7.

CONCLUSION

The significant prolongation of transplant survival achieved by corticosteroids alone (P < 0.001) is again significantly increased by combining them with CTLA4-Ig (P < 0.001). Specific immunotherapy combined with nonspecific steroid therapy may also improve clinical corneal transplantation results. Compared to the two control groups, CTLA4-Ig and anti-CD154 only influenced transplant survival at a low dosage (P < 0.001).

Effects of brain mineralocorticoid receptor blockade on blood pressure and renal functions in DOCA-salt hypertension

In normotensive rats, we have previously demonstrated a role of brain mineralocorticoid receptors in blood pressure and renal function control. In the present study, the coordinate cardiovascular and renal effects of brain mineralocorticoid receptor blockade were examined by intracerebroventricular (i.c.v.) administration of a selective mineralocorticoid receptor antagonist (RU28318; 3,3-oxo-7 propyl-17-hydroxy-androstan-4-en-17yl-propionic acid lactone) in rats with hypertension induced by deoxycorticosterone acetate (DOCA) and salt. DOCA pellets were implanted s.c. in male Wistar rats given 0.9% NaCl as drinking solution 3 or 5 weeks before assessment of the effects of i.c.v. injection of RU28318 on cardiovascular and renal functions. Changes in expression of brain angiotensinogen, atrial natriuretic peptide (ANP) and mineralocorticoid receptor mRNA in specific brain areas in 3-week DOCA-salt rats were evaluated by in situ hybridization. The rise in systolic blood pressure induced by DOCA-salt treatment was most marked during the first 3 weeks. At 3 and 5 weeks after implantation of the DOCA-pellets a single i.c.v. injection of 10 ng of RU28318 significantly decreased systolic blood pressure during 24 h as assessed at 2, 8 and 24 h, while heart rate was not altered. Increased urinary excretion of water and electrolytes was observed in 3- and 5-week DOCA-salt rats during the period 0-8 h after i.c.v. injection of RU28318 while the suppressed plasma renin activity was not affected. The expression of brain angiotensinogen, ANP and mineralocorticoid receptor mRNA was not altered by 3-week DOCA-salt treatment, but 3 h after i.c.v. injection of RU28318, mineralocorticoid receptor mRNA expression in hippocampal cell fields responded with an increase of about 40%. In conclusion, these results demonstrate that in rats with hypertension induced by DOCA-salt, brain mineralocorticoid receptor blockade affects renal function and blood pressure regulation.

Ovarian hormones modulate endothelin-1 vascular reactivity and mRNA expression in DOCA-salt hypertensive rats

We previously demonstrated a differential activation of the endothelin-1 (ET-1) pathway in male and female deoxycorticosterone (DOCA)-salt hypertensive rats, with the male rats exhibiting marked alterations in vascular and pressor responses to ET-1 and Suc-[Glu,(9)Ala(11,15)]-ET-1(8-21) (IRL-1620), an ET(B) agonist. Mechanisms underlying these gender differences are unclear, and we hypothesized that the ovarian hormones attenuate vascular ET(B) responses in female DOCA-salt rats. Female Wistar rats were randomized in 3 groups: sham-operated, ovariectomized (OVX), and OVX plus hormone replacement with estradiol (E) or estradiol/progesterone (EP). Two weeks later, rats were uninephrectomized and further randomized in DOCA-salt (subcutaneous injections of desoxycorticosterone and drinking water containing NaCl/KCl) and control normotensive (subcutaneous injections of vehicle and tap water). Blood pressure was evaluated both by direct and standard tail-cuff methods. Responses to IRL-1620 were evaluated in vivo/in situ in the mesenteric microcirculation. mRNA expression of ET-1 and ET(A/B) receptors was evaluated in mesenteric arteries by reverse transcription-polymerase chain reaction and expressed relative to GAPDH. OVX-DOCA rats developed a more severe form of hypertension than did DOCA rats. Treatment with E or EP restored blood pressure to levels observed in DOCA rats. In the mesentery, IRL-1620 induced vasodilatation in control rats, a mild vasoconstriction in DOCA rats, and marked vasoconstriction in OVX-DOCA rats. Both E and EP decreased IRL-1620-induced vasoconstriction in the DOCA group. In the normotensive group, OVX did not change blood pressure or IRL-1620-induced vasodilation. Removal of the ovaries increased ET-1 mRNA in arteries from DOCA and control rats, although treatment with E or EP reversed these changes. Vascular ET(B) receptor mRNA levels were greatly enhanced in OVX-DOCA but not OVX-control rats. Hormone replacement with E or EP restored ET(B) receptor expression in the DOCA group. A greater blood pressure-lowering effect of bosentan (ET(A)/ET(B) blocker) was observed in OVX-DOCA rats. The observation that OVX worsens hypertension as well as the altered ET(B) receptor-mediated responses and the effects of bosentan in female DOCA rats supports our suggestion that the ovarian hormones modulate ET-1/ET(B) receptor vascular responses/expression in DOCA-salt hypertension.

Glomerular osteopontin expression and macrophage infiltration in glomerulosclerosis of DOCA-salt rats

Expression of the chemoattractant osteopontin (OPN) may contribute to macrophage infiltration in many types of tubulointerstitial kidney disease, but the role of OPN in chronic glomerulosclerosis is unknown. We hypothesized that glomerular OPN expression and macrophage infiltration occur in deoxycorticosterone acetate (DOCA)-salt glomerulosclerosis in rats. Uninephrectomized rats receiving DOCA pellets and 1% saline were compared with control rats. OPN mRNA was determined by Northern blot, and OPN protein was determined by Western blot. The localization of OPN was studied by in situ hybridization and double immunohistochemistry with glomerular cell markers. Macrophage infiltration was quantified by counting ED-1-positive cells, and semiquantitative glomerulosclerosis scores were obtained. In DOCA-salt rats, OPN mRNA in the kidney was increased 2-fold over control after 9 days and 3 weeks and 20-fold after 6 weeks. Tubulointerstitial OPN staining was apparent after 21 days of DOCA treatment. Glomerular OPN mRNA and protein was detected after 42 days in parietal and visceral epithelial cells, activated myofibroblasts, and occasionally mesangial cells. Progressive glomerular macrophage infiltration occurred during the development of DOCA hypertension, paralleling the degree of glomerulosclerosis. Glomeruli staining positive for osteopontin contained more macrophages (18.4 +/- 3.4 per cross-section) than osteopontin-negative glomeruli (3.6 +/- 0.5; P < 0.05). Glomerular OPN expression occurs in chronic hypertensive glomerulosclerosis and is associated with macrophage infiltration. The data suggest a role for OPN as a chemoattractant in hypertensive glomerulosclerosis.

Central bromocriptine-induced tachycardia is reversed to bradycardia in conscious, deoxycorticosterone acetate-salt hypertensive rats

A central dopaminergic origin has been demonstrated for the bromocriptine-induced tachycardia in conscious, normotensive rats. The present study investigated the effect of bromocriptine on heart rate and the principal site of action of this agonist in conscious, deoxycorticosterone acetate-salt hypertensive rats, in which altered central dopaminergic activity has been previously reported. Intravenous administration of bromocriptine (150 microg/kg) increased heart rate (49+/-5 beats/min.) in uninephrectomized control rats, while it induced a significant bradycardia (50+/-6 beats/min.) in deoxycorticosterone acetate-salt hypertensive rats. In the latter animals, intravenous (500 microg/kg) or intrathecal (40 microg/rat at T9-T10) pretreatment with domperidone, a selective dopamine D2 receptor antagonist that does not cross the blood-brain barrier, reduced partially, but significantly, the bradycardiac responses to bromocriptine (reduction of about 44% and 48% of the maximal effect, respectively). In contrast, the bromocriptine-induced bradycardia was fully abolished by intravenous pretreatment with metoclopramide (300 microg/kg), a dopamine D2 receptor antagonist that crosses the blood-brain barrier, or by combined pretreatment with intravenous and intrathecal domperidone. These results indicate that, in deoxycorticosterone acetate-salt hypertensive rats, bromocriptine decreases rather than increases heart rate, an effect that is mediated partly through a peripheral D2 dopaminergic mechanism and partly through stimulation of spinal dopamine D2 receptors. They further support the concept that, in normotensive, conscious rats, the central tachycardia of bromocriptine appears to predominate and to mask the bradycardia of this agonist at both peripheral and spinal dopamine D2 receptors.

A novel formulation for controlled release of heparin-DOCA conjugate dispersed as nanoparticles in polyurethane film

Heparin is a potent anticoagulant agent that interacts strongly with antithrombin III to prevent the formation of fibrin clot. In this study, we propose a new method for preparing a heparin-releasing system using a simple solvent casting. The heparin-DOCA conjugate, having an amphiphilic property, was homogeneously mixed with polyurethane in the co-solvent of dioxane, propanol and water. After casting the film, heparin-DOCA was homogeneously dispersed as nanoparticles in a polyurethane film. As the loading amount of heparin-DOCA in the film was increased, nanoparticle size, water uptake, and release rate were increased. Moreover, the percentage of released amount of heparin-DOCA was increased with the increase in the loading amount of heparin-DOCA. This was because the size of heparin-DOCA particles increases with the increase in the loading amount of heparin-DOCA, thereby decreasing the distance between particles and the total diffusion length to the surface. The release rate of heparin-DOCA can be controlled by the amount of the drug being loaded and the film thickness. When the heparin-DOCA loaded on the polyurethane films was above 7.5%, the released heparin-DOCA prevented the formation of fibrin clot and the platelet adhesion on the film surface.

Serotonergic mechanisms of the lateral parabrachial nucleus on DOCA-induced sodium intake

It has been shown that the serotonergic mechanisms of the lateral parabrachial nucleus (LPBN) inhibit NaCl intake in different models of angiotensin II (ANG II)-dependent NaCl intake in rats. However, there is no information about the involvement of LPBN serotonergic mechanisms on NaCl intake in a model of NaCl intake not dependent on ANG II like deoxycorticosterone (DOCA)-induced NaCl intake. Therefore, in this study we investigated the effects of bilateral injections of serotonergic agonist and antagonist into the LPBN on DOCA-induced 1.8% NaCl intake in rats. Male Holtzman rats were treated with s.c. DOCA (10 mg/rat each every 3 days). After a period of training, in which the rats had access to 1.8% NaCl during 2 h for several days, the rats were implanted with stainless steel cannulas bilaterally into the LPBN. Bilateral injections of the serotonergic receptor antagonist methysergide (4 microg/0.2 microl each site) in the LPBN increased 1.8% NaCl intake (32.2+/-3.9 versus vehicle: 15.0+/-1.6 ml/2 h, n=10) and water intake (12.5+/-3.5 versus vehicle: 3.2+/-1.0 ml/2 h). Injections of the serotonergic 5HT(2A/2C) receptor agonist DOI (5 microg/0,2 microl each site) in the LPBN reduced 1.8% NaCl intake (6.8+/-1.7 versus saline: 12.4+/-1. 9 ml/2 h, n=10) and water intake (2.2+/-0.8 versus saline: 4.4+/-1.0 ml/2 h). Besides the previously demonstrated importance for the control of ANG II-dependent water and NaCl intake, the data show that the serotonergic inhibitory mechanisms of the LPBN are also involved in the control of DOCA-induced NaCl intake.

Clofibric acid or diethylmaleate supplemented diet decrease blood pressure in DOCA-salt treated male Sprague Dawley rats--relation with liver antioxidant status

The effects of 8-week diethylmaleate (DEM) and clofibric acid (CFA) supplemented diet on blood pressure, body and liver weights, liver antioxidant status and nitric oxide synthase (NOS) activity were investigated in 8-week DOCA-salt treated and untreated Sprague-Dawley male rats. It appeared that DEM and particularly CFA treatments were associated with a significant decrease in blood pressure in DOCA-salt treated rats, and an accentuation of the decreases in body weights in both diet supplemented groups. This was not associated with increases in NO production in the liver. In contrast, hepatic lipid peroxidation was significantly decreased in both DOCA-salt treated and untreated groups on DEM and particularly on CFA supplemented diet. The protective effects of CFA and DEM against hepatic cellular damage could be involved in the decreases in blood pressure in DOCA-salt treated rats, where CFA was more efficient than DEM. In CFA supplemented groups, there was a strong increase in hepatic superoxide dismutase (SOD), glutathione-peroxidase (GSH-Px), and catalase (CAT) activities and in DEM supplemented groups, increases in SOD and CAT activities and in GSH levels were observed. Our data suggest that normalization of blood pressure in DOCA-salt treated rats by CFA was due to an enhancement of the half-life of NO while DEM increased its availability.

Myocardial renin is neither necessary nor sufficient to initiate or maintain ventricular hypertrophy

We tested the hypothesis that the myocardial renin-angiotensin system (RAS) is both necessary and sufficient to initiate and maintain all classes of ventricular hypertrophy. Myocardial and plasma renin and angiotensinogen were measured in rats during initiation and maintenance of ventricular hypertrophy associated with DOCA implants and 1% NaCl drinking water, with and without the AT(1) ANG II receptor blocker losartan. Additional groups of rats were given a low-sodium diet (0.04%) for 3 wk. Ventricular hypertrophy was initiated within 7 days and maintained for 35 days in DOCA-treated rats despite significantly low myocardial and plasma renin, normal or low myocardial and plasma angiotensinogen, or the presence of losartan. Furthermore, there was no ventricular hypertrophy in low-salt diet-fed animals despite increased myocardial and plasma renin levels and normal angiotensinogen levels. Therefore, the myocardial RAS is not necessary to initiate or maintain cardiac hypertrophy in DOCA-treated rats and is not sufficient to initiate cardiac hypertrophy in low-salt diet-fed rats. Additionally, myocardial renin and angiotensinogen were significantly correlated with corresponding plasma levels.

Genetic isolation of a chromosome 1 region affecting susceptibility to hypertension-induced renal damage in the spontaneously hypertensive rat

Linkage studies in the fawn-hooded hypertensive rat have suggested that genes influencing susceptibility to hypertension-associated renal failure may exist on rat chromosome 1q. To investigate this possibility in a widely used model of hypertension, the spontaneously hypertensive rat (SHR), we compared susceptibility to hypertension-induced renal damage between an SHR progenitor strain and an SHR congenic strain that is genetically identical except for a defined region of chromosome 1q. Backcross breeding with selection for the markers D1Mit3 and Igf2 on chromosome 1 was used to create the congenic strain (designated SHR.BN-D1Mit3/Igf2) that carries a 22 cM segment of chromosome 1 transferred from the normotensive Brown Norway rat onto the SHR background. Systolic blood pressure (by radiotelemetry) and urine protein excretion were measured in the SHR progenitor and congenic strains before and after the induction of accelerated hypertension by administration of DOCA-salt. At the same level of DOCA-salt hypertension, the SHR.BN-D1Mit3/Igf2 congenic strain showed significantly greater proteinuria and histologically assessed renal vascular and glomerular injury than the SHR progenitor strain. These findings demonstrate that a gene or genes that influence susceptibility to hypertension-induced renal damage have been trapped in the differential chromosome segment of the SHR.BN-D1Mit3/Igf2 congenic strain. This congenic strain represents an important new model for the fine mapping of gene(s) on chromosome 1 that affect susceptibility to hypertension-induced renal injury in the rat.

Roles of brain angiotensin II and C-type natriuretic peptide in deoxycorticosterone acetate-salt hypertension in rats

OBJECTIVE

To investigate the roles of brain angiotensin II and C-type natriuretic peptide (CNP) in the hypertensive mechanism of deoxycorticosterone acetate (DOCA)-salt hypertension.

METHODS

We injected 50 microg/kg CV-11 974, an angiotensin II type-1 receptors antagonist, 30 nmol/kg CNP-22, or the vehicle (artificial cerebrospinal fluid) into the cerebral ventricle or intravenously 5 min before the intracerebroventricular infusion of 1.5 mol/I NaCl solution for 30 min into either male normotensive Wistar rats or DOCA-salt hypertensive rats anesthetized with urethane, and their arterial pressures and heart rates were continuously recorded. Blood (2 ml) was collected at the end of the infusion for the measurement of plasma concentration of arginine vasopressin. We infused 10 or 50 microg/kg per day CV-11 974, 10 or 50 nmol/kg per day CNP-22, or the vehicle (1 microl/h) into the cerebral ventricles of DOCA-salt hypertensive rats for 7 days by using osmotic minipumps, and measured their systolic arterial pressures, pulse rates, and urinary excretions of vasopressin.

RESULTS

Intracerebroventricular pre-administrations of CV-11 974 and of CNP-22 inhibited increases in mean arterial pressure, heart rate, and plasma vasopressin concentration induced by intracerebroventricular infusion of 1.5 mol/l NaCl into normotensive rats; increases in hemodynamics and plasma level of vasopressin induced by intracerebroventricular infusion of 1.5 mol/l NaCl were suppressed by intracerebroventricular pre-injections of CV-11 974, but not of CNP-22, into DOCA-salt hypertensive rats. Continuous intracerebroventricular infusions of 50 microg/kg per day CV-11 974 attenuated hypertension in DOCA-salt treated rats, accompanied by a reduction in urinary excretion of vasopressin. Continuous intracerebroventricular infusions of 50 nmol/kg per day CNP-22, however, affected neither hypertension nor urinary excretion of vasopressin in DOCA-salt hypertensive rats.

CONCLUSION

Brain angiotensin II could play a role in the pressor mechanism of DOCA-salt hypertension by increasing release of vasopressin via type 1 receptors. That brain CNP has an inhibitory effect on release of vasopressin in acute experiments indicates that the impairment of this inhibitory effect of brain CNP on secretion of vasopressin could be involved in the pathogenesis of DOCA-salt hypertension in rats.

Enhanced blood pressure sensitivity to deoxycorticosterone in mice with disruption of bradykinin B2 receptor gene

The renal kallikrein-kinin system is activated under conditions of mineralocorticoid excess. To evaluate whether endogenous kinins exert a protective role against the development of mineralocorticoid-induced hypertension, we studied the cardiovascular effects induced by long-term administration of deoxycorticosterone (DOC; 0.3 micromol/g body wt s.c. once per week for 6 weeks) or vehicle in transgenic mice (Bk2r-/-) lacking the bradykinin B2 receptor gene and in wild-type controls (Bk2r+/+). Under basal conditions, Bk2r-/- mice showed higher systolic blood pressure (tail-cuff plethysmography) than wild-type Bk2r+/+ and heterozygous Bk2r+/- mice (121+/-2 versus 114+/-2 and 115+/-2 mm Hg, respectively; P<0.05 for both comparisons). Heart rate was higher in Bk2r-/- and Bk2r+/- than in Bk2r+/+ (459+/-12 and 418+/-7 versus 390+/-7 bpm; P<0.05 for both comparisons). Systolic blood pressure was increased by DOC in transgenic as well as in wild-type mice, whereas no change was induced by the vehicle. The pressor response to DOC was more rapid and pronounced in Bk2r-/- than in Bk2r+/+ and Bk2r+/- (30+/-5 versus 15+/-4 and 6+/-3 mm Hg, respectively, at 3 weeks; P<0.01 for both comparisons). The difference in systolic blood pressure was consistent with that detected by direct intra-arterial measurements of mean blood pressure. Neither DOC nor its vehicle altered heart rate or gain in body weight over time. Under basal conditions, urinary sodium excretion did not differ between strains. During DOC administration, cumulative urinary sodium excretion was lower in Bk2r-/- than in Bk2r+/+ (2.59+/-0.15 versus 3.31+/-0.22 mmol, respectively, during the first week; P<0.05). Urinary kinin excretion was increased by DOC in both Bk2r-/- (from 0.65+/-0.17 to 4.27+/-0.80 pmol/24 h; P<0.01) and Bk2r+/+ (from 0.55+/-0.09 to 6.27+/-1.48 pmol/24 h; P<0.05). The increase in urinary kinin excretion was similar between strains. These results show that integrity of the bradykinin B2 receptor is essential for regulation of blood pressure and heart rate under basal conditions. In addition, they indicate that activation of the kallikrein-kinin system represents a compensatory response against the development of hypertension induced by mineralocorticoid excess.

Lower than normal expression of brain nitric oxide synthase gene in the hypothalamus of deoxycorticosterone acetate-salt hypertensive rats

OBJECTIVE

To elucidate the role of brain nitric oxide produced by neuronal constitutive nitric oxide synthase in sodium-induced hypertension.

DESIGN AND METHODS

Diets containing a high (8% NaCl), a medium (2% NaCl), and a low (0.2% NaCl) sodium content were administered to Wistar rats aged 12 weeks for 10 days or 8 weeks until they were killed. Male Wistar rats administered either deoxycorticosterone acetate, 1% NaCl or both and the respective controls were killed 2 weeks (during prehypertensive stage) or 6 weeks (during hypertensive stage) after the start of treatment. The hypothalamus and lower brainstem were excised for extraction of total RNA. Reverse transcription polymerase chain reactions of constitutive nitric oxide synthase messenger RNA and glyceraldehyde-3-phosphate dehydrogenase messenger RNA were performed, and constitutive nitric oxide synthase messenger RNA levels were expressed relative to glyceraldehyde-3-phosphate dehydrogenase messenger RNA levels.

RESULTS

A high sodium intake for 10 days tended to decrease constitutive nitric oxide synthase messenger RNA levels in the hypothalamus, compared with effect of a low sodium intake. Constitutive nitric oxide synthase messenger RNA levels in the hypothalamus of deoxycorticosterone acetate-salt hypertensive rats were lower than those in the control sham-operated rats. Neither alteration of sodium intake nor administration of deoxycorticosterone with and without sodium affected constitutive nitric oxide synthase gene expression in the lower brainstem.

CONCLUSIONS

Expression of neuronal constitutive nitric oxide synthase gene is downregulated in the hypothalamus of deoxycorticosterone acetate-salt hypertensive rats. This lower than normal expression of neuronal constitutive nitric oxide synthase gene in the hypothalamus could be an adaptive response to sodium-induced hypertension, and suggests that nitric oxide produced by hypothalamic constitutive nitric oxide synthase plays a role in maintenance of blood pressure in relation to sodium balance in rats.

Arterial function in mineralocorticoid-NaCl hypertension: influence of angiotensin-converting enzyme inhibition

Angiotensin-converting enzyme inhibitors have been suggested to improve the function of arterial endothelium and smooth muscle not only through inhibition of angiotensin II formation and reduction of blood pressure, but also via additional pathways, e.g. potentiation of endogenous kinins and enhancement of endothelial autacoid formation. Therefore, we investigated whether 10-week-long quinapril therapy (10 mg kg-1 day-1) could beneficially influence the function of mesenteric arterial rings in vitro in deoxycorticosterone-NaCl-treated Wistar-Kyoto rats, a model of hypertension which is known to be resistant to angiotensin-converting enzyme inhibition. The quinapril treatment had no long-term blood pressure-lowering effect nor did it reduce the associated cardiac hypertrophy in deoxycorticosterone-NaCl hypertension. In noradrenaline-precontracted arterial rings the endothelium-dependent relaxations to acetylcholine and adenosine 5'-diphosphate as well as the endothelium-independent relaxations to nitroprusside and isoprenaline were clearly attenuated in the deoxycorticosterone-NaCl-treated rats. However, the quinapril therapy was without significant effect on any of these dilatory responses. In the presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, the relaxations to acetylcholine in untreated and quinapril-treated hypertensive animals were practically absent, whereas in normotensive rats distinct relaxations to higher concentrations of acetylcholine were still present. Interestingly, when endothelium-dependent hyperpolarization was prevented by precontracting the preparations with potassium chloride, no differences were found in relaxations to acetylcholine and adenosine 5'-diphosphate between the study groups. Exogenous bradykinin induced small comparable contractions in endothelium-intact mesenteric arterial rings from all study groups. In conclusion, the 10-week-long quinapril therapy did not have any significant effects on arterial function in deoxycorticosterone-NaCl hypertensive rats. Therefore, the present results stress the roles of reduced blood pressure and diminished angiotensin II formation in the beneficial vascular effects of long-term angiotensin-converting enzyme inhibition in the present model of hypertension. Furthermore, since the relaxations to acetylcholine and adenosine 5'-diphosphate in the deoxycorticosterone-NaCl-treated rats were attenuated in the absence and presence of nitric oxide synthase inhibition but not under conditions which prevented hyperpolarization, impaired endothelium-dependent relaxation to agonists can be attributed to diminished endothelium-dependent hyperpolarization in this model of hypertension.

Renal sodium pump regulation in deoxycorticosterone salt hypertension in the rat

The renal sodium pump participates in sodium homeostasis and has been predicted to have a role in salt dependent forms of hypertension. However, the status of the renal sodium pump in volume-dependent hypertension is unclear. We assessed the renal sodium pump and its activity in the deoxycorticosterone acetate (DOCA)-salt model in rats, a model of volume-dependent hypertension. Sprague-Dawley rats on ad libitum diet were compared with four groups of litter mates receiving high or low salt diets, with or without DOCA administration. The renal sodium pump evaluation included measurement of hydrolytic activity, ouabain binding capacity and affinity, sodium activation, active pump units (determined by phosphoenzyme level), dephosphorylation rate, and isoform specific molecular expression. Intrinsic enzyme properties, including sodium and ouabain affinities, as well as turnover rate per sodium pump, were identical among the five groups. In contrast, the combination of DOCA and high salt intake (DOCA high salt) produced marked, significant increases in hydrolytic activity, ouabain binding capacity, phosphoenzyme level, and alpha1-isoform expression. DOCA low salt animals showed much smaller but significant increases in pump number. We conclude that DOCA and volume expansion may each alter renal sodium pump regulation, but volume expansion is clearly dominant. Increased renal sodium pump activity in DOCA high salt animals would, if unmitigated, favor sodium reabsorption and may contribute to hypertension.

Evaluation of protein and peptide hydrolases in DOCA-salt hypertensive rat treated with chlorthalidone

We have reported that chlorthalidone (Chlor) prevents the development of heart hypertrophy in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The present study was carried out to determine whether Chlor (8 mg/day per animal, added to the food, for 20 days) affects kidney and heart hypertrophy in DOCA-salt (8 mg/kg, sc, twice a week) rats by causing alterations in protein and peptide hydrolysis. Heart (left ventricle) and kidney enzyme activities were measured in tissue homogenates from normal-control, salt-control, DOCA-salt and DOCA-salt-Chlor male Wistar rats (N = 6 for each group), using azocasein as the substrate for proteolytic enzymes and specific peptides for prolylendopeptidase (PEP) and multicatalytic proteinase (MCP). The tissue weight/body weight ratio increased in parallel to elevation of blood pressure. The left ventricular muscle hypertrophy (26%, P < 0.05) present in the DOCA-salt hypertensive group was completely prevented by simultaneous Chlor treatment. Chlor treatment did not change the kidney hypertrophy (+79%, P < 0.;05) observed in the salt-control (+57%, P < 0.05) and DOCA-salt (+74%, P < 0.05) groups. The hydrolysis of peptides by PEP and MCP was similar in the normal and salt-control groups. The heart PEP activity was 24% higher (P < 0.01) in DOCA-salt rats, whereas MCP activity was not different when compared to control groups. DOCA-salt treatment increased MCP activity in the kidney by 44% while PEP activity did not differ from that of control groups. The hydrolysis of proteins by heart enzymes was increased by salt by 47%. Chlor treatment restored the reduction in protein hydrolysis induced by DOCA-salt (a 21% decrease, P < 0.05) to a level similar to that of the normal-control group. Similarly, Chlor coadministration prevented the 30% reduction in renal proteolytic activity elicited by DOCA-salt treatment. Although Chlor treatment prevented the DOCA-salt-induced reduction in protein hydrolysis, this response did not interfere with kidney hypertrophy. The mechanism by which hypertension produces hypertrophy is unclear, but our results suggest that this structural modification is not related to the activities of some peptidases, e.g. protein and peptide hydrolases.

Hypotensive effect of crude root extract of Solanum sisymbriifolium (Solanaceae) in normo- and hypertensive rats

The hypotensive effect of the crude hydroalcoholic extract from root of Solanum sisymbriifolium Lam. (Solanaceae) was investigated both in normotensive and hypertensive rats. The intravenous administration of the extract (50 and 100 mg/kg) produced a significant decrease in blood pressure in anaesthetized hypertensive (adrenal regeneration hypertension + deoxycorticosterone acetate (ARH + DOCA)) rats. Oral administration of the extract (10, 50, 100 and 250 mg/kg) also produced a dose-dependent hypotensive effect in conscious hypertensive animals. In anaesthetized normotensive rats, the extract (50 and 100 mg/kg, i.v.) also induced hypotension in a dose-dependent manner. Lastly, no significant effect on blood pressure was produced by the extract when administered orally (10, 50, 100, 250, 500 and 1000 mg/kg) to conscious normotensive rats.

Effects of central alpha-adrenergic agonists on hormone-induced 3% NaCl and water intake

Male rats received intracerebroventricular (ICV) renin (600 ng) or daily subcutaneous injections of deoxycorticosterone (5 mg) to induce 3% NaCl and water intake. Noradrenaline (NOR; 40-160 nmol) and clonidine (CLO; 5-20 nmol) injected ICV induced 70 to 100% inhibition of the intakes. Phenylephrine (PHE; 40-160 nmol) injected ICV induced 60 to 95% inhibition of the intakes. NOR and PHE induced a stronger inhibition on the 3% NaCl intake induced by renin than on the intake induced by deoxycorticosterone (DOC), and CLO did the opposite. CLO was always more effective than PHE to induce inhibition of the intakes. The results suggest that NOR inhibits hormone (angiotensin II, aldosterone)-induced NaCl intake by acting mainly on alpha 2-adrenergic receptors.