Effects of the endothelin ETA-receptor antagonist FR139317 on development of hypertension and cardiovascular hypertrophy in deoxycorticosterone acetate-salt hypertensive rats

We investigated the role of endothelin-1 (ET-1) in the development of hypertension and cardiovascular hypertrophy in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Two weeks after the start of DOCA-salt treatment, the rats were divided into two groups and were given FR139317 [(R)2-[(R)-2-[(S)-2-[[1-(hexahydro-1H-azepinyl)]- carbonyl]amino-4-methyl-pentanoyl]amino-3-[3-(1-methyl-1H-indolyl)] propionyl]amino-3-(2-pyridyl) propionic acid], a specific ETA-receptor antagonist, or its vehicle for 2 weeks. Uninephrectomized rats without DOCA-salt treatment served as controls. Vehicle-treated DOCA-salt rats developed marked hypertension after 4 weeks. FR139317 significantly suppressed the increase in systolic blood pressure with values averaging 163 +/- 8 mmHg (P < 0.05 vs DOCA-salt rats receiving vehicle, 195 +/- 9 mmHg). Morphological studies in the rats given the vehicle showed vascular medial hypertrophy, with a significant increase in the wall area and wall-to-lumen ratio. A marked decrease in vascular wall hypertrophy was observed in the FR139317-treated DOCA-salt rats. The cardiac hypertrophy in DOCA-salt hypertensive rats was also significantly reduced by FR139317. Therefore, these results suggest that ET-1 plays an important role in the development of DOCA-salt hypertension presumably by stimulating the ETA receptor. In addition, we found that an ETA-receptor antagonist effectively reduced cardiovascular hypertrophy in the rats, so the cardiovascular hypertrophy noted in DOCA-salt hypertensive rats may be related to ET-1.

Increased responsiveness and decreased expression of G proteins in deoxycorticosterone hypertension

Deoxycorticosterone-salt (DOCA-salt) hypertension is characterized by elevated vasoconstriction to agonists that stimulate G protein-mediated activation of phospholipase C. However, the mechanisms responsible for the augmented responsiveness are unknown. This study tested the hypothesis that this augmented vascular responsiveness is due to elevated content of G(alpha)q, the G protein alpha-subunit that activates phospholipase C. Thoracic aortae from DOCA-salt hypertensive rats (systolic blood pressure 183 +/- 7 mm Hg) and normotensive controls (systolic blood pressure 115 +/- 2 mm Hg) were homogenized and G protein content determined. Western analysis revealed that G(alpha)i content was decreased in DOCA compared with control rats (1364 +/- 196 versus 2343 +/- 188 densitometry units, P < or = .05) with no differences observed for G(alpha)q or G(alpha)s. In addition, contractile responses in denuded femoral artery strips revealed a significant decrease in EC50 values in DOCA arteries to all of the agonists examined: aluminum fluoride (DOCA = 1.42, control = 2.34 mmol/L), mastoparan (DOCA = 0.51, control = 35 micromol/L), phenylephrine (DOCA = 0.08, control = 0.53 micromol/L), and serotonin (DOCA = 0.014, control = 0.04 micromol/L, EC20 values). Finally, arteries from DOCA rats contracted with aluminum fluoride had increased sensitivity to G protein antagonists but not to a phospholipase C inhibitor. The enhanced contractile responsiveness in the DOCA arteries may be mediated in part through decreased G(alpha)i levels. However, it is not caused by increased concentrations of G(alpha)q in the cell membrane or by increased phospholipase C sensitivity, and the increased constrictor response to G protein stimulators of phospholipase C appears to depend primarily on increased G protein sensitivity.

Adult height in women with early-treated congenital adrenal hyperplasia (21-hydroxylase type): relation to body mass index in earlier childhood

To investigate if obesity, as judged by increased body mass index (BMI), during childhood is associated with impaired adult stature in patients with 21-hydroxylase-type congenital adrenal hyperplasia (CAH), a retrospective analysis was carried out on outpatient records of 30 girls with CAH who had reached adult height. Height SD score for age (HtSDS(ca)), HtSDS for bone age (HtSDS(ba)), BMI and steroid dosage in early childhood (3.2-4.6 years) and later childhood (7.2-9.1 years), were compared with adult HtSDS (HtSDS(adlt)), adult HtSDS less mid-parental HtSDS (HtSDS(adlt)-HtSDS(mp)), predicted adult height SDS (HtSDS(pdct)), adult height SDS less predicted adult HtSDS (HtSDS(adlt)-HtSDS(pdct)) and age at menarche. Mean (SD) for HtSDS(adlt) was -1.13 (1.05), mean HtSDS(pdct) -0.12 (0.9) and mean age at menarche 13.5 (1.9) years. BMI in childhood was not correlated with HtSDS(adlt) but showed negative correlations with HtSDS(adlt)-HtSDS(mp) (r = -0.43; p < 0.02) and HtSDS(adlt)-HtSDS(pdct) (r-0.45; p < 0.02). BMI in later childhood showed negative correlations with HtSDS(adlt)-HtSDS(pdct) (r = -0.61; p < 0.001) and age at menarche (r = -0.63; p < 0.001). We conclude that in girls with early-treated CAH, a high BMI during early childhood is associated with loss of genetic height potential, and in later childhood with over-prediction of adult height and early menarche.

Role of endothelin-1 in hypertension induced by long-term inhibition of nitric oxide synthase

We examined the effect of long-term nitric oxide (NO) synthase inhibition on vascular and renal endothelin-1 levels and evaluated the antihypertensive effect of endothelin ETA receptor antagonist FR139317 ((R)2(-)[(R)-2(-)[(S)-2(-)[[1-(hexahydro-1H-azepinyl)]- carbonyl]amino-4-methyl-pentanoyl]amino-3(-)[3-(1-methyl-1H- indolyl)]propionyl]amino-3-(2-pyridyl) proprionic acid] on rats in which NO synthase was blocked. Chronic NO blockade was produced by oral administration of the NO synthase inhibitor NG-nitro-L-arginine for 4 weeks, which produced sustained hypertension. At the end of this time, there were no significant changes in aortic and renal immunoreactive-endothelin levels between NG-nitro-L-arginine-treated hypertensive rats and normotensive control rats. Intravenous injection of FR139317 (10 mg/kg), which had a sufficient hypotensive effect on deoxycorticosterone acetate-salt hypertensive rats, to NG-nitro-L-arginine-treated hypertensive rats produced only a moderate hypotensive effect, to the same degree as seen in normotensive rats. The results indicate that long-term NO synthase inhibition did not affect vascular and renal endothelin-1 levels in these rats. It seems likely that endothelin-1 and ETA receptors do not contribute to the sustained hypertension induced by NO synthesis blockade.

Calpain activity of hypertrophic hearts from hypertensive rats

Heart tissue contains large amounts of the Ca(2+)-activated proteinase calpain which has been assigned a specific function in the turnover of muscle protein. The objective of the present study was to determine calpain (E.C. 3.4.22.17)-like activity in homogenates of left ventricle from hypertensive rats that developed ventricular hypertrophy. Calpain activity was assayed using heat-denatured azocasein as a substrate in the presence of 1 mM calcium and corrected by subtraction of the Ca(2+)-independent activities. The latter were measured in the presence of 1 mM EGTA and the products read at 440 nm. Male Wistar rats (225 g) were assigned to control (N = 8, normal drinking water), salt (N = 6, drinking water containing 1% NaCl) and DOCA-salt (N = 6, deoxycorticosterone acetate, 8 mg/kg, sc, twice a week for 20 days plus drinking water containing 1% NaCl) groups. SHR (N = 6, spontaneously hypertensive rats) were also used. The calpain activity of the control group was at 3.90 +/- 0.22 mU/g wet weight tissue. Hypertension induced significant left ventricular hypertrophy in DOCA-salt rats (26%) and in SHR (54%) and a 30% decrease in calpain activity in both groups (P < 0.01). In the high salt load (salt group) calpain activity was also decreased, but this was not accompanied by hypertrophy. In the present indirect measurement of protein degradation capacity of heart tissue homogenates the proteolytic activity was activated (221%) by 1 mM calcium and inhibited (84%) by 1 mM EGTA after a 48-h incubation period, indicating the destruction of the calpain inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of tetrandrine on left ventricle hypertrophy in deoxycorticosterone acetate-salt hypertensive rats

The effect of regression of left ventricular hypertrophy was studied in deoxycorticosterone-acetate-salt hypertensive rats (DOCA-salt hypertensive rats) treated with tetrandrine. Treatment with tetrandrine (by gastric intubation, 50 mg/kg per day for 9 weeks) lowered systolic blood pressure, left ventricular weight, Ca2+ of mitochondria, and markedly decreased the density (Bmax) and total number of dihydropyridine binding sites in hypertrophic left ventricle (P < 0.001). There was no difference between groups in dissociation constant (Kd) values of dihydropyridine binding sites. These facts indicate that tetrandrine decreased cardiac mass in DOCA-salt hypertensive rats through mechanisms that may be associated with the density and the total number of dihydropyridine binding sites, Ca2+ and blood pressure control.

Subcutaneous administration of desoxycorticosterone pivalate for the treatment of canine hypoadrenocorticism

Twelve dogs with hypoadrenocorticism were treated with subcutaneous desoxycorticosterone pivalate (DOCP). Eight of these dogs were recently diagnosed and had not yet been treated. Four dogs previously had been diagnosed and treated (three with intramuscular DOCP, one with oral fludrocortisone acetate). History, physical examination, serum electrolytes, and blood urea nitrogen (BUN) were evaluated. Desoxycorticosterone pivalate (2.2 mg/kg body weight) was administered every 25 days. On day 0, recently diagnosed dogs had a median serum sodium concentration of 131.5 mEq/L, median serum potassium concentration of 6.6 mEq/L, and median BUN of 41.5 mg/dl. All subsequent median serum electrolyte and BUN concentrations were normal. All previously treated dogs had normal blood values which were maintained throughout the study.

19-Acetylenic-deoxycorticosterone inhibits 19-hydroxylase and 11 beta-hydroxylase activities in dispersed bovine zona fasciculata cells

19-Acetylenic-deoxycorticosterone (19-A-DOC) is believed to be a competitive irreversible inhibitor of the synthesis of 19-nor-deoxycorticosterone (19-nor-DOC), a potent mineralocorticoid implicated in some forms of human and animal hypertension. It has been shown to inactivate 11 beta/19-hydroxylase in hamster adrenal mitochondria. Dispersed bovine zona fasciculata cells were incubated for one hour with 1.5 x 10(-8) M ACTH and 0, 1, 10, or 100 microM 19-A-DOC and tritiated deoxycorticosterone (DOC) substrate. Steroids were separated using two sequential thin-layer chromatography systems and their tritium content was counted and corrected for recovery. The 19-A-DOC decreased synthesis of 19-hydroxydeoxycorticosterone, the precursor of 19-nor-DOC. The inhibitor also impaired 11-hydroxylation of DOC to form corticosterone. The data suggest that 19-A-DOC is an effective inhibitor of 11 beta/19-hydroxylase activity in dispersed bovine adrenal cells.

Desoxycorticosterone pivalate in the management of canine primary hypoadrenocorticism

Primary hypoadrenocorticism in dogs may be poorly responsive to oral fluorocortisone treatment. Desoxycorticosterone pivalate is a suggested alternative treatment in these and all other cases of hypoadrenocorticism. Primary hypoadrenocorticism was diagnosed in a 3-year-old Cocker Spaniel bitch. Treatment with oral fluorocortisone at a dose rate of 0.13 mg 5 kg-1 d-1 was ineffective at maintaining serum electrolyte concentrations within normal limits. Administration of DOCP at a dose of 1.6-2.2 mg kg-1 intramuscularly every 28 d over a 5-year period, successfully maintained normal serum sodium and potassium concentrations. Side-effects encountered were minimal and were dose- or disease-related.

Enhanced vascular responsiveness to Bay K 8644 in mineralocorticoid- and N-nitro arginine-induced hypertension

The present study evaluates the response to the L-type voltage gated calcium channel agonist Bay K 8644 in two forms of experimental hypertension (mineralocorticoid- and hypertension induced by the nitric oxide synthase inhibitor N omega-nitro-L-arginine (N-Nitro arginine)) and under conditions of acute stretch. These studies test the hypothesis that increased L-type calcium channel activity in vasculature is a hallmark or general characteristic of hypertension. Male Sprague-Dawley rats were made hypertensive by subcutaneous implantation of deoxycorticosterone acetate (200 mg/kg DOCA) and given normal or high salt water (1% NaCl + 0.2% KCl); other rats were made hypertensive by ingestion of N-Nitro arginine (2% in water). Systolic blood pressures (SBP) were taken by the standard tail cuff method. Following development of hypertension, rats were anesthetized, and aortae or mesenteric arteries were isolated for measurement of isometric contractile force. Cumulative concentration response curves to Bay K 8644 (10(-10) to 10(-6) M), KCl (6 to 100 mM), or phenylephrine (10(-10)-3 x 10(-7) M) were evaluated. Isolated mesenteric arteries from rats given both DOCA and salt were most sensitive to Bay K 8644 (SBP = 191 +/- 6 mmHg, -log EC50 = 7.78 +/- 0.13), followed by rats receiving high salt alone (SBP = 118 +/- 6 mmHg, -log EC50 = 7.30 +/- 0.17), DOCA alone (SBP = 152 +/- 2 mmHg, -log EC50 = 7.25 +/- 0.15), and finally normal sham rats (SBP = 111 +/- 5 mm Hg, -log EC50 > or = 6.80 +/- 0.10). These data indicate that both DOCA and salt intake can independently influence responsiveness to Bay K 8644.(ABSTRACT TRUNCATED AT 250 WORDS)

[Diffuse xanthogranuloma as a cause of infantile heterochromia]

A 7-month-old female infant presented with a heterochromia and an anisocoria. A spontaneous hyphema and a secondary glaucoma had developed. Under topical and systemic steroid therapy the eye improved continuously. At the time of the last ocular examination the hyphema had resorbed, and the intraocular pressure was normal. Heterochromia had almost completely vanished, and dilation of the pupil was much better. Since even a massive juvenile xanthogranuloma of the iris responds well to steroids, operative and radiation treatment should be limited to cases refractory to antiinflammatory drug therapy.

Induction of hypertension and cardiac hypertrophy in guinea pig by DOCA salt

Experimental hypertension can be induced in rats by uninephrectomy, administration of deoxycorticosterone acetate (DOCA) and sodium chloride. We developed this model in the guinea pig, because it presents an isoenzymic myosin pattern and calcium-induced calcium release similar to those of humans. Unilateral nephrectomy was performed in 33 guinea pigs, after which they were given DOCA (300 mg/kg pellets, s.c.; n = 11, or 10 mg, i.m.; n = 12, 5 days a week for 5 weeks). One week after surgery, drinking water was supplemented with NaCl 9 g/l and KCl 2 g/l for 5 weeks. Control guinea pigs (n = 10) were nephrectomized but not treated. Five weeks after surgery, hemodynamic measurements were recorded and the animals sacrificed to assess the degree of left ventricular hypertrophy. Left ventricular hypertrophy was considered significant if the ratio of left ventricular weight/body weight was > 2.3 and if the thickness of the left ventricle free wall was > 3.5 mm. Results showed that the systolic, diastolic and mean blood pressures of the treated groups were 36% higher than in the control group. Cardiac hypertrophy occurred within 5 weeks, and resulted in an increase in left ventricle weight and in left ventricular hypertrophy. The possibility of using the DOCA salt model of experimental hypertension in the guinea pig could help to elucidate the mechanisms responsible for hypertension and induced left ventricular hypertrophy, and thus improve prevention and treatment.

Administration time-dependent change in the effect of spironolactone in rats

The present study was undertaken to examine whether the natriuretic effect of spironolactone, a competitive antagonist of mineralocorticoid, varies with its time of administration. Wistar rat maintained under the condition of light from 7 hr to 19 hr were divided into two groups. The first group had a bilateral adrenalectomy and received a 50-mg deoxycorticosterone acetate (DOCA) tablet intraperitoneally (DOCA group). The second group had a sham operation (control group). Spironolactone (50 mg/kg) was given orally at 12 hr or 24 hr, and the 8-hr urine was collected. At the end of the experiment, the blood sample for measurement of aldosterone was obtained at 12 hr and 24 hr in the control group. The natriuretic effect of spironolactone in the 24 hr-trial was significantly greater than that of the 12 hr-trial in the control group. However, such a time-dependent difference was diminished and did not reach statistical significance in the DOCA group. The plasma aldosterone concentration at 24 hr was significantly higher than that at 12 hr in the control group. These results suggest that the natriuretic effect of spironolactone varies with its time of administration. Daily variation in mineralocorticoid activity might be involved in this chronopharmacological phenomenon of spironolactone.

[Microsurgery of the nose and paranasal sinuses; concept, technique and result]

1. The close relationship between an impaired nasal air passage or chronic diseases of the paranasal sinuses and the bronchial system seems to be generally accepted. 2. Any improvement of the nasal respiration and chronic infections of the sinuses obviously have a positive effect on pathologic lung function, bronchitis and asthma. Even though a causal connection between the treatment of the chronic nasal and paranasal infection and the decrease of pulmonary symptoms in chronic bronchitis and asthma could not be verified yet by valuable statistics, the transnasal surgery reduces heavy nasal symptoms in more that 90% of our cases. 3. We consider endonasal microsurgery to be the safest and most convenient technique in the treatment of chronic nasal and paranasal diseases. This minimal invasive surgery therefore is suitable as well for the treatment of recurrent diseases which unfortunately cannot be avoided in this area.

Long-term mineralocorticoid-induced changes in rat neuron properties plus interaction of aldosterone and ANG II

The central site of action and the neuronal mechanism of the robust sodium appetite initiated in rats by the synergistic action of a peripheral priming with mineralocorticoid [deoxycorticosterone acetate (DOCA)] and subsequent central angiotensin II (ANG II) were investigated using iontophoretic and electrophysiological techniques in urethan-anesthetized, DOCA-pretreated (0.5 mg/day sc for 3 days) or nonpretreated male Wistar rats. A significantly greater number of spontaneously active neurons were recorded in the medial septum and median preoptic area, but not in the cortex, in rats pretreated with DOCA than found in the nonpretreated animals (9.3 +/- 1.2 per electrode descent; n = 19 vs. 6.1 +/- 0.7 per descent; n = 21; P < 0.001). The firing rate of the spontaneously active neurons was also significantly increased in the DOCA-pretreated animals. A greatly increased neuronal sensitivity (increased activity lasting up to 10 min after the end of the application) to iontophoretically applied ANG II was found in 32% of the ANG II-sensitive neurons in pretreated animals. This prolonged response was never observed in the nonpretreated animals. Iontophoretically applied aldosterone produces rapid neuronal excitation in both groups of rats and renders previously insensitive neurons sensitive to iontophoretically applied ANG II only in the DOCA-pretreated animals. This forebrain region, therefore, contains neurons that undergo a mineralocorticoid pretreatment-induced and/or a rapid aldosterone-induced sensitization to ANG II, which may be the neuronal mechanism whereby a persistent sodium appetite, induced by the synergistic action of these two hormones, is stimulated.

Toxicity of desoxycorticosterone pivalate given at high dosages to clinically normal beagles for six months

Desoxycorticosterone pivalate was administered IM to juvenile Beagles at 0, 2.2, 6.6, or 11 mg/kg of body weight daily over a consecutive 3-day period every 28 days (equivalent to a cumulative monthly dosage of 0, 6.6, 19.8, or 33 mg/kg) for 6 months. Polyuria, polydipsia, and decreases in serum potassium and BUN concentrations were detected while the dogs were being treated. Transient increases in serum sodium concentrations also were detected. The treated males had significant decreases in body weight gain, resulting in an 18% decrease in body weight in the 11-mg/kg dosage group, compared with the controls. The weights of the adrenal glands, epididymides, and testes also were lower in the treated males. Organ weights for the 2.2, 6.6, and 11-mg/kg dosage groups were: 86, 79, and 69%, respectively, of the controls (adrenal glands); 80, 70, and 68%, respectively, of the controls (epididymides); and, 79, 75, and 67%, respectively, of the controls (testes). When normalized to body weight, these decreases in organ weight were still dosage-dependent, but the differences were less remarkable. In contrast, the relative weight (to body weight) of the kidneys (males and females) and of the thyroid and parathyroid glands (males) were higher dosage-dependently. All of the treatment-related effects, other than organ and body weight changes, appeared to be reversible following the cessation of treatment. On the basis of these results, it was concluded that treatment with desoxycorticosterone pivalate could be tolerated, even when given at dosage 15-fold the therapeutic dosage of 2.2 mg/kg every 25 days.

[Plasma renin activity and angiotensin converting enzyme of renal brush borders]

The present experiment was undertaken to examine the relationship between plasma renin activity and the concentration of angiotensin converting enzyme (ACE) in plasma and renal brush border of Wistar Kyoto rats. Different experimental models known to have opposite effects on plasma renin activity were used: changes in salt intake, the deoxycorticosterone acetate (DOCA) and DOCA-salt models and the two-kidneys one clip (2K1C) model. Two weeks after the start of these experimental series, the rats were killed. At this time, blood pressure did not differ from control group, even in the 2K1C and DOCA-salt groups. As expected, PRAs were highest in the 2K1C and depleted salt groups and lowest in the DOCA, DOCA-salt and high salt groups. No relationship between this wide variation in PRA and change of ACE activity in both plasma and renal brush border could be observed. In the plasma, ACE activity in sodium-depleted rats was slightly decreased whereas no change occurred in the other models. In the kidney, DOCA treatment led to increased ACE activity in the brush border only if the animals were maintained on a high salt intake. DOCA or NaCl alone failed to have this effect. In the 2K1C model, the clipped kidneys exhibited increased brush border ACE activity whereas the unclipped kidneys did not show any significant variation in ACE activity, when compared to sham operated rats. In summary, on one hand these findings show that variations in ACE activity were linked neither to hypertension nor to changes in PRA.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of estrogen and adrenocorticoids on adenocarcinoma induction by 1,2-dimethylhydrazine in male rats

Groups of male Sprague-Dawley rats at 39 days of age, were injected s.c. with estradiol benzoate (15 micrograms/kg), cortisone acetate (2.5 mg/kg) and deoxycorticosterone acetate (10.0 mg/kg) in peanut oil, the controls receiving the oil vehicle on days 1 and 3 and weekly thereafter for a total of 32 injections. 1,2-Dimethylhydrazine was administered s.c. weekly after the 1st 2 drug doses, the dosage as base being 9.0 mg/kg for the 1st 7 injections, then 19.4 mg/kg for the last 13 dosages. The rats were killed 31 weeks after the 1st DMH injection. The changes in animal condition at necropsy were moderate to extreme in half of the rats and all survived the 20 DMH injection-schedule; mortality was low per group but elevated with the deoxycorticosterone acetate treatment (40%). Essentially all rats displayed colon adenocarcinomas and the total frequency and the number in the proximal and distal portions were in the control ranges except for the statistically significant decrements in overall and distal colon numbers for the estrogen-treated group and possibly, near-significance in case of the cortisone acetate-injected rats. Small intestinal adenocarcinomas which were more prevalent in the upper areas occurred among the groups. As based on the current findings with estrogen, the trend was in the direction of an inhibiting effect on DMH tumorigenesis in contrast to a stimulatory response reported for androgenized males.

[Intracochlear placement of cochlear implant electrodes in soft surgery technique]

It is commonly accepted that the intracochlear placement of the cochlear implant electrode is potentially damaging to the hearing rests which may exist. Consequently, cochlear implants have been recommended for totally deaf ears only. The question has been raised whether or not it is possible to preserve residual hearing during intracochlear implantation through extremely careful surgical techniques. Experience has shown, that the cochleotomy of the scala tympani anterior to the round window niche, careful preservation of the fibrine endost layer and the use of Healon are amongst the surgical procedures described which may assist in retaining the rest function of the inner ear. These observations which are discussed in detail suggest that the experienced surgeon can effect preservation of residual hearing for patients who cannot derive significant benefits from conventional acoustic amplifiers.

Metabolic studies of uridine in rats with DOCA-salt hypertension and on high sodium diet

1. The steady-state metabolic clearance and calculated secretion rate of the pyrimidine nucleoside uridine were studied by equilibrium infusion in normal rats, rats on a high sodium diet, rats made hypertensive by subcutaneous injection of deoxycorticosterone acetate (DOCA), unilateral nephrectomy and high sodium drinking fluid, and two control groups of rats for the hypertensive group. 2. Basal plasma uridine concentration in DOCA-salt hypertension rats was found to be significantly reduced to 3.99 +/- 0.31 mumol/L (mean +/- s.e.m.) compared with control rats (11.98 +/- 1.64 mumol/L). Metabolic clearance (MCR) in DOCA-salt hypertensive rats was significantly raised (200.54 +/- 10.77 mL/kg per min) compared with control rats (65.17 +/- 1.99 mL/kg per min). No difference was found in plasma uridine concentration and MCR among the other two control groups and high sodium diet rats. Calculated secretion rate was unchanged in all animals. No significant differences were found between different groups of rats in blood pressure responses to uridine. 3. The raised metabolic clearance and reduced plasma uridine concentration in DOCA-salt hypertension may be consistent with increased intracellular transport and phosphorylation of uridine to the physiologically active compound uridine monophosphate (UMP) which would lead to arteriolar constriction, hypertension and natriuresis. The results contrast with those in humans with extracellular fluid (ECF) expansion from endstage renal failure and rats with one-kidney, one-clip (1K1C) hypertension but are not due to the pharmacological effects of deoxycorticosterone. The difference may be due to the haemodynamic consequences of reduced renal perfusion pressure or reduced renal mass compared with DOCA-salt model.

Efficacy of microcrystalline desoxycorticosterone pivalate for treatment of hypoadrenocorticism in dogs. DOCP Clinical Study Group

The efficacy of microcrystalline desoxycorticosterone pivalate (DOCP) therapy was evaluated in 60 dogs with hypoadrenocorticism. Fifty-one of the dogs were being treated with either DOCP or fludrocortisone acetate prior to entering the study. The disease had been recently diagnosed in 9 dogs that were not under maintenance treatment prior to entering the study. Desoxycorticosterone pivalate (2.2 mg/kg of body weight, IM) was administered on days 0, 25, and 50. Physical examination was performed, and blood samples were obtained for serum biochemical analysis (Na+, K+, and BUN concentrations) on days 0, 14, 25, 39, 50, 64, and 75. On day 75 of the study, a final physical examination was performed and the course of treatment was evaluated. Sixty-eight percent (41/60) of the dogs had normal physical findings on day 0 vs 87% (52/60) on day 75. Mean (+/- SD) body weight increased from 24.8 +/- 12.7 kg on day 0 to 26.2 +/- 13.7 kg on day 75. Mean serum Na+ (137.7 +/- 8.5 mEq/L) and K+ (5.6 1.0 mEq/L) concentrations and Na(+)-to-K+ ratio (25.4 +/- 5.0:1) were outside normal reference limits on day 0. By day 75, serum Na+ (144.3 +/- 4.8 mEq/L) and K+ (4.9 +/- 0.8 mEq/L) concentrations and Na(+)-to-K+ ratio (30.4 +/- 5.1:1) were normal and were significantly (P < 0.01) improved, compared with the corresponding values on day 0. Of the 60 dogs, 58 (97%) regained the loss in body weight, appetite, and muscular strength while given DOCP; once achieved, these improvements were maintained. These 58 dogs did not vomit or have diarrhea, common problems in dogs with hypoadrenocorticism.(ABSTRACT TRUNCATED AT 250 WORDS)

Ouabain as an amplifier of mineralocorticoid-induced hypertension

Ouabain has recently been reported to be an endogenous Na, K-ATPase inhibitor. To evaluate whether it exerts hypertensive action itself or amplifies the hypertensive action of small doses of mineralocorticoids, 5 mg deoxycorticosterone acetate (DOCA), 1 mg ouabain, or a combination of both were injected into mononephrectomized rats weekly for 6 weeks, and changes in blood pressure were evaluated. The blood pressures of control, DOCA-treated, ouabain-treated, and the combination treatment group at the sixth week were 138 +/- 3 (SE), 160 +/- 6, 144 +/- 6, and 201 +/- 14 mmHg, respectively. The blood pressure of rats given DOCA or ouabain alone was not significantly different from that of controls. In contrast, the blood pressure of rats given the combination of DOCA and ouabain was significantly higher than that of control rats and those given DOCA or ouabain separately. Cardionephromegaly and histopathological changes found in rats given the combination of DOCA and ouabain were consistent with the effects of an elevation of blood pressure. Further evaluation revealed that the amplification effect of ouabain on the hypertensive action of DOCA was dose dependent, with the minimum dose that caused the amplification effect being 0.25 mg/week. These results indicate that ouabain, although devoid of hypertensive action itself, amplifies the hypertensive action of small doses of DOCA and can cause a hypertensive state similar to that induced by larger doses of DOCA. It is inferred that the amplification effect of ouabain on mineralocorticoids is important in the genesis of hypertension.

The influence of high salt intake and/or chronic blood volume expansion on renin-angiotensin system in Brattleboro rats

The influence of chronic saline drinking and/or DOCA-salt treatment on plasma renin activity and renal renin concentration was studied in vasopressin-deficient homozygous (DI) Brattleboro rats and their vasopressin-secreting heterozygous (non-DI) littermates. The activity of renin-angiotensin system (RAS) can be suppressed even in the absence of vasopressin under the conditions of a sufficiently high salt intake that is achieved in DI rats by consumption of 0.6% saline instead of water. An almost complete RAS suppression in both plasma and kidney was observed in young animals in which high salt intake induced not only blood volume expansion but also blood pressure elevation, i.e. in mildly hypertensive unilaterally nephrectomized saline drinking DI rats as well as in moderately hypertensive DOCA-salt treated DI rats and in non-DI rats with a severe DOCA-salt hypertension. Our results indicate that intravascular expansion and blood pressure changes are important factors for the modulation of plasma and renal renin activity even in the absence of vasopressin.

The pathogenesis of DOCA-salt hypertension

Deoxycorticosterone acetate (DOCA) is an agent commonly used to induce hypertension in experimental animals. This form of hypertension is dependent on altered regulation of central pressor mechanisms including the brain renin-angiotensin system. Additionally, there are characteristic changes involving the cardiovascular system and baroreflex responses. This review will discuss aspects of the pathogenesis of DOCA hypertension and the effect of various antihypertensive agents on the development of this form of hypertension.