Interleukin-1beta administered intracerebroventricularly stimulates the release of noradrenaline in the hypothalamic paraventricular nucleus via prostaglandin in the rat

We evaluated the effect of intracerebroventricular (i.c.v.) administration of interleukin (IL)-1beta on the rectal temperature and the release of noradrenaline (NA) in the hypothalamic paraventricular nucleus (PVN) of the rat. IL-1beta increased rectal temperature at doses ranging from 300 pg to 300 ng, whereas it, at doses ranging from 3 ng to 300 ng, significantly stimulated the release of NA in the PVN measured by intracerebral microdialysis. The stimulatory effect of IL-1beta on the release of NA was blocked by the subcutaneous injection of indomethacin. These findings suggest that IL-1beta stimulates the release of NA in the PVN via prostaglandin, and that the release of NA in the PVN is not necessarily related to the increase in body temperature.

Potentiation of natriuretic peptide action by the beta-adrenergic blocker carvedilol in hypertensive rats: a new antihypertensive mechanism

Treatment with a beta-adrenergic blocker (beta-blocker) in hypertension is associated with increased plasma atrial natriuretic peptide (ANP) levels despite a decrease in cardiac overload. The mechanism and pathophysiological significance of the phenomenon remain unclear. To clarify the role of the ANP system in the antihypertensive effects of the beta-blocker, we investigated the effects of carvedilol (30 mg/kg x day, orally, for 4 weeks) on the ANP system in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm). Plasma ANP levels showed a significant increase despite a significant decrease in blood pressure and heart rate in the carvedilol group. Although ANP messenger RNA levels in the heart did not change, messenger RNA levels of the natriuretic peptide-C (NP-C) receptor as a clearance receptor showed a significant decrease in both the aorta and lung in the carvedilol group. NP-C receptor densities were also significantly decreased in the lung in this group. The biological half-life of exogenous ANP in circulating blood was prolonged in the carvedilol group compared with that in the control group. Administration of the ANP receptor antagonist, HS-142-1, resulted in a greater increase in systolic blood pressure in the carvedilol group than in the control group. In addition, both basal and ANP-stimulated cGMP contents in the aorta were significantly higher in the carvedilol group. These results suggest that carvedilol potentiates the hypotensive action of ANP by increasing plasma ANP levels and enhancing the vascular response to ANP. These effects were closely related to the down-regulation of the NP-C receptor. The newly found mechanism seems to account for a sizable portion of the antihypertensive effects of carvedilol and could be of potential importance in the treatment of cardiovascular disease with beta-blockers.

Roles of heme oxygenase/carbon monoxide system in genetically hypertensive rats

Although carbon monoxide (CO) has been suggested to be involved in the regulation of cardiovascular function through activation of soluble guanylyl cyclase, the pathophysiological significance in hypertension remains unknown. We therefore examined the effects of heme oxygenase (HO) inhibitor zinc protoporphyrin IX (ZnPP-IX) on blood pressure and determined HO mRNA expression level in various tissues in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm) and Wistar Kyoto rats (WKY/Izm). Although ZnPP-IX significantly increased systolic blood pressure in both strains, the increment of blood pressure was larger in SHR-SP/Izm than in WKY/Izm. An essentially similar increase of blood pressure was demonstrated even in the ganglion blocker-pretreated rats. Constitutive type HO-2 mRNA levels in the aorta and kidney and inducible type HO-1 mRNA levels in the cardiac ventricle were significantly increased in SHR-SP/Izm compared with WKY/Izm. Clearly these results indicate the importance of the endogenous HO/CO system in the peripheral tissues in genetically hypertensive rats.

Nitric oxide synthase I immunoreactivity in the macula densa of the kidney is angiotensin II dependent

The present study was undertaken to clarify the mechanism of the regulation of nitric oxide synthase (NOS)-I in the macula densa of the kidney. We determined the changes in NOS-I immunoreactivity of the macula densa relevant to the changes in systemic blood pressure (BP) and the renin-angiotensin system. Rats received four different types of treatment, and kidney sections were immunohistochemically stained for renin, NOS-I, and NOS-III. Plasma renin activity (PRA) and angiotensin II (Ang II) concentration were determined by radioimmunoassay. In the low-salt group, PRA, plasma Ang II, and the number of renin and NOS-I positively stained areas in the juxtaglomerular apparatus (JGA) were all increased, while BP and NOS-III in the glomerular capillaries did not change. In the desoxycorticosterone acetate (DOCA)-salt group, in contrast to the elevation of BP, PRA, plasma Ang II, and all immunohistochemical parameters were decreased. In the Ang II infusion group, BP, plasma Ang II, and the number of NOS-I positive glomeruli were increased, while PRA and renin staining were decreased. Administration of Ang II type 1 receptor (AT-1) antagonist TCV-116 significantly increased PRA, plasma Ang II, and the number of renin-positive glomeruli. However, BP, and NOS-I and NOS-III staining did not show any difference. These results clearly suggest that NOS-I in the macula densa changes in parallel with plasma Ang II, but not renin or systemic BP.

Brain beta-endorphin and other opioids are involved in restraint stress-induced stimulation of the hypothalamic-pituitary-adrenal axis, the sympathetic nervous system, and the adrenal medulla in the rat

Opiates and opioids have complex effects on the hypothalamic-pituitary-adrenal axis, and they stimulate the sympathetic nervous system. This study was designed to clarify the role of brain beta-endorphin in the mechanism by which stress increases plasma concentrations of adrenocorticotropin (ACTH), epinephrine (E), and norepinephrine (NE). Intracerebroventricular (i.c.v.) administration of beta-endorphin to rats significantly increased plasma ACTH levels at doses of 0.09, 0.3, and 1.5 nmol, and plasma E and NE levels at doses of 0.3 and 1.5 nmol. The rise of plasma ACTH, E, and NE levels by 0.3 nmol beta-endorphin was inhibited by intravenous (i.v.) administration of 2 mg/kg b.wt. naloxone. I.v. administration of anti-rat corticotropin-releasing hormone (CRH) rabbit serum completely blocked the beta-endorphin-induced ACTH secretion without affecting the secretion of E and NE. I.c.v. administration of anti-beta-endorphin rabbit gamma-globulin attenuated a 30-min restraint stress-induced rise of plasma ACTH levels without significant influence on the rise of E and NE levels, whereas i.v. administration of naloxone attenuated the restraint stress-induced rise of plasma ACTH, E and NE levels. These results suggest that i.c.v. administration of beta-endorphin stimulates the secretion of ACTH, E, and NE through opiate receptor, and that brain CRH mediates the beta-endorphin-induced secretion of ACTH. The results also suggest that brain beta-endorphin is, at least in part, involved in the restraint stress-induced stimulation of the hypothalamic-pituitary-adrenal axis, and that some opioids other than beta-endorphin are involved in the stimulatory mechanism of the autonomic nervous system and the adrenal medulla in the rat.

Desmopressin stimulation test for diagnosis of ACTH-dependent Cushing's syndrome

We evaluated the usefulness of a desmopressin (DDAVP) test in the diagnosis of ACTH-dependent Cushing's syndrome. After an intravenous injection of 5 microg DDAVP, plasma ACTH levels increased to more than 200% of the basal levels in 10 of 10 patients with Cushing's disease, but remained less than 150% in all of 11 normal subjects, 3 patients with Addison's disease, 5 cases of Cushing's disease in remission, and 3 patients with ectopic ACTH syndrome. Peak levels of plasma cortisol after the DDAVP stimulation were 159 +/- 14% in the patients with Cushing's disease, and less than 150% of the basal levels in the other 5 groups. We also found a case of Cushing's disease with periodicity which responded to DDAVP only in the active stage. In vitro studies revealed that DDAVP directly stimulates ACTH release from corticotropic adenoma cells through V1b but not V2 vasopressin receptors. In conclusion, the DDAVP stimulation test, i.e., determination of plasma ACTH levels after 5 microg DDAVP injection, seems useful for discriminating Cushing's disease from normality, and may serve to facilitate the differentiation between Cushing's disease and ectopic ACTH syndrome.

Interrelation between nitric oxide synthase and heme oxygenase in rat endothelial cells

The gene expression and interrelation of the constitutive type nitric oxide (NO) synthase-III as a NO-forming enzyme and heme oxygenase-2 as a carbon monoxide-forming enzyme were studied in cultured rat aortic endothelial cells. Both NO synthase-III and heme oxygenase-2 mRNAs were demonstrated in the endothelial cells by RNAase protection analysis. NO synthase-III mRNA was upregulated in the presence of the heme oxygenase inhibitor, zinc protoporphyrin IX, but not in the presence of the NO synthase inhibitor, N(G)-nitro-L-arginine. Although heme oxygenase-2 mRNA was significantly upregulated in the presence of both NO synthase inhibitor and heme oxygenase inhibitor, the increase was greater with the NO synthase inhibitor. These results provide the first evidence for the concomitant gene expression of NO synthase-III and heme oxygenase-2, and their compensatory interrelation in endothelial cells.

Anabolic effects of 1,25-dihydroxyvitamin D3 on osteoblasts are enhanced by vascular endothelial growth factor produced by osteoblasts and by growth factors produced by endothelial cells

Human osteoblast-like cells (HOB) produce vascular endothelial growth factor (VEGF), the steady state level of which is stimulated by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. As osteoblasts and endothelial cells are proximally located in skeletal tissue, we investigated the anabolic effects of 1,25-(OH)2D3 and VEGF on HOB cocultured with endothelial cells. When HOB with high alkaline phosphatase (Al-P) activity and human umbilical vein endothelial cells (HUVEC) with little activity were cultured together, Al-P activity increased, accompanied by an increase in cell number. When HOB and HUVEC were cultured separately, 1,25-(OH)2D3 did not directly stimulate [3H]thymidine incorporation into HUVEC, but stimulated it in the presence of HOB. VEGF did not directly stimulate the Al-P activity of HOB but stimulated it in the presence of HUVEC. The conditioned medium of HOB stimulated the proliferation of HUVEC, and this was partially blocked by anti-VEGF antibody. Conversely, the conditioned medium of HUVEC increased Al-P activity and [3H]thymidine incorporation into HOB, and this was partially blocked by antiinsulin-like growth factor I antibody and BQ-123, a specific antagonist of the endothelin-1 (ET-1) receptor. 1,25-(OH)2D3 stimulated the release of VEGF and ET-1 from HOB and HUVEC, respectively. Furthermore, the 1,25-(OH)2D3-induced release of VEGF was enhanced in HOB cocultured with HUVEC. A quantitative reverse transcription-PCR study revealed that genes for VEGF receptors (Flt-1 and KDR) were expressed in HUVEC, but not in HOB, and that 1,25-(OH)2D3 increased the levels of expression of VEGF receptor genes in endothelial cells only when cocultured with HOB. In summary, we demonstrated that 1,25-(OH)2D3 exerts an anabolic effect on osteoblasts by enhancing their production of VEGF, which stimulates its receptors on endothelial cells, followed by increased production of osteotropic growth factors, such as insulin-like growth factor I and ET-1. These in vitro findings suggest that the VEGF/VEGF receptor system may be involved in both bone formation and bone remodeling in vivo.

Saccharated ferric oxide (SFO)-induced osteomalacia: in vitro inhibition by SFO of bone formation and 1,25-dihydroxy-vitamin D production in renal tubules

A 60-year-old man with portal hypertensive gastropathy due to type C liver cirrhosis developed severe bone pains, marked hypophosphatemia with inappropriately increased urinary excretion of phosphate (%TRP; 9.6%), and hyperalkaline phosphatasia, after intravenous administration of saccharated ferric oxide (SFO) at a dose of 80-240 mg/week over a period of more than 5 years. The total iron infused was estimated to be more than 25 g. On a diagnosis of SFO-induced osteomalacia, the infusion of iron was immediately discontinued, and phosphate and vitamin D2 (1000 IU/day) were administered. Serum levels of 25-OHD2 increased after 1 week, whereas levels of 1,25-(OH)2D2 did not increase until 3 months later, accompanied by improvement of renal tubular reabsorption of phosphate and gradual improvement of the bone pains. The patient has been doing well for the last 2 years, with normal serum levels of phosphate, calcium, and alkaline phosphatase, without any supplementation of phosphate, vitamin D, or iron-containing agents. In primary culture of neonatal mouse renal tubules, in which 1,25-(OH)2D3 was produced from 25-OHD3 in response to PTH, SFO significantly inhibited PTH-induced production of 1,25-(OH)2D3 at 30 mumol/L, which is attainable in the urine of patients receiving a therapeutic intravenous dose of SFO. Furthermore, SFO decreased the calcium content and inhibited 45Ca incorporation in cultured fetal mouse parietal bones at 3 mumol/L. Such SFO concentration may be transiently observed in the plasma of patients receiving excessive intravenous doses of SFO for a prolonged period. These in vitro findings together with the clinical observations suggest that SFO, after filtration through the glomerulus and reabsorption in the proximal renal tubules, impaired proximal renal tubular function, such as tubular reabsorption of phosphate and 1 alpha-hydroxylase activity, leading to hypophosphatemic osteomalacia. Furthermore, it is highly likely that SFO in the peripheral blood, when transferrin is saturated with iron, may impair bone formation and aggravate osteomalacia. Although SFO-induced osteomalacia is reversible simply by discontinuation of the agent, excessive and prolonged administration of SFO should be avoided.

Left ventricular hypertrophy is more prominent in patients with primary aldosteronism than in patients with other types of secondary hypertension

We determined functional and morphological changes of the heart by 2-dimensional and pulse Doppler echocardiography in 20 patients with primary aldosteronism and compared the results with those in 50 healthy normotensive subjects, 12 patients with Cushing's syndrome, 9 patients with pheochromocytoma, and 47 patients with essential hypertension. All hypertensive groups had greater left ventricular mass indexes than did the normotensive group (76.9 +/- 17.2 g/m2). Despite similar age distribution, blood pressure during antihypertensive treatment, and duration of hypertension, the primary aldosteronism group had a significantly greater left ventricular mass index (152.5 +/- 42.5 g/m2) than did the Cushing's syndrome (103.4 +/- 37.5 g/m2), pheochromocytoma (122.4 +/- 28.5 g/m2), and essential hypertension (101.4 +/- 32.8 g/m2) groups. The left ventricular posterior wall thickness and interventricular septal wall thickness were significantly greater in the hypertensive groups than in the normotensive group and also significantly greater in the primary aldosteronism group than in any of the other hypertensive groups. By contrast, there were no significant differences among the four hypertensive groups in any variable of systolic or diastolic function of the heart. The results suggest that left ventricular hypertrophy is more pronounced in patients with primary aldosteronism than in patients with other forms of hypertension. It is therefore important to echocardiographically evaluate cardiac hypertrophy as a risk factor of morbidity and mortality in patients with this low renin hypertension.

Antihypertensive and vasculo- and renoprotective effects of pioglitazone in genetically obese diabetic rats

Although an improvement of insulin sensitivity has been shown to be a new therapeutic approach for treating diabetes mellitus, details of effects of this treatment on the cardiovascular system and possible renal complications remain unknown. In the present study, we investigated the effects of a thiazolidine derivative, pioglitazone, and examined the insulin-sensitizing action on blood pressure, nephropathy, and vascular changes in genetically obese diabetic Wistar fatty (WF) rats. Pioglitazone (3 mg.kg-1.day-1) was orally administered for 13 wk starting at the age of 5 wk, and the results were compared with those of vehicle-treated WF rats. At the age of 18 wk, vehicle-treated WF rats were associated with mild hypertension, nephropathy with proteinuria histological glomerular injury, and renal arteriolosclerosis in addition to hyperglycemia, hyperinsulinemia, and hyperlipidemia. Treatment with pioglitazone significantly improved glucose and lipid metabolism. In addition, it lowered blood pressure, decreased proteinuria, and prevented glomerular injury, renal arteriolosclerosis, and aortic medial wall thickening, whereas body weight, food intake, sodium balance, and urinary norepinephrine excretion were significantly increased. These results suggest that the insulin-sensitizing agent pioglitazone is effective in correcting not only glucose and lipid metabolism but also cardiovascular and renal complications in non-insulin-dependent diabetes mellitus.

Increased concentration of vascular endothelial growth factor/vascular permeability factor in cyst fluid of enlarging and recurrent thyroid nodules

Human thyrocytes produce vascular endothelial growth factor (VEGF), a potent angiogenic factor, also known as vascular permeability factor (VPF), which increases vascular permeability. Based on the assumption that VEGF/VPF is involved in fluid accumulation in thyroid cysts, we determined the VEGF/VPF concentration in cyst fluids of thyroid nodules from 79 patients. VEGF/VPF was found to be abundantly present in the cyst fluids (0.02-183 ng/mL). There was no significant difference of VEGF/VPF concentration in the cyst fluid obtained from thyroid adenoma or from adenomotous goiter with cystic degeneration. Immunoreactive VEGF/VPF in cyst fluid was eluted mainly at 45 kDa, and stimulated endothelial cell proliferation, which was partially blocked by anti-VEGF/VPF antibody. The VEGF/ VPF concentration in the cyst fluid obtained from patients who required repeated aspiration or underwent surgical resection because of recurrent accumulation (84.8 +/- 58.3 ng/mL, mean +/- SD, n = 18) was significantly higher than that in the cysts that regressed or disappeared after a single aspiration (4.3 +/- 4.4 ng/mL, n = 12, P < 0.001). These in vitro and clinical findings suggest that VEGF/VPF is at least partly involved in the accumulation of cyst fluid in thyroid nodules, and that a high VEGF/VPF concentration predicts rapid accumulation of the cyst fluid, possibly necessitating interventional treatment.

Corticotropin-releasing factor up-regulates its own receptor gene expression in corticotropic adenoma cells in vitro

To investigate the expression of CRF receptor (CRF-R) in human corticotropic adenoma (hCA) cells, we analyzed messenger RNA (mRNA) levels of type-1 CRF-R (CRF-R1). Adenomas were obtained from 10 patients with Cushing's disease. Northern blot analysis using a rat CRF-R1 complementary RNA probe revealed a main hybridization band of 2.7 kilobases in all the hCAs. The CRF-R1 mRNA level significantly increased after 1 h, reached 15-fold the basal level at 8 h, and remained elevated 24 h after the addition of 10 nmol/L CRF in vitro. Dose dependency of the stimulatory effect of CRF was also demonstrated in hCA cells, whereas CRF down-regulated CRF-R1 mRNA levels in rat anterior pituitary (AP) cells. Treatment with dexamethasone or vasopressin decreased the CRF-R1 mRNA level in hCA cells, as observed in rat AP cells. In conclusion, we detected CRF-R1 mRNA in all hCAs tested. The CRF-R1 mRNA level was up-regulated by CRF itself in cultured hCA cells, in contrast to the down-regulation in rat AP cells.

Gene expression of endothelial type isoform of nitric oxide synthase in various tissues of stroke-prone spontaneously hypertensive rats

Nitric oxide (NO) has been suggested to play important roles in the pathophysiology of various cardiovascular diseases. This study tested the hypothesis that an attenuated biological action of NO in hypertension is attributed to a change in the gene expression of NO synthase (NOS), a key enzyme involved in NO formation. The expression level of mRNA of endothelial type NOS (NOS-III) was determined in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm) and Wistar Kyoto rats (WKY/Izm) by ribonuclease protection assay using a partial clone as probe. NOS-III mRNA was expressed ubiquitously in various tissues of WKY/Izm and SHR-SP/Izm either at 5 wk or 13 wk of age. There was no significant difference in the tissue expression of NOS-III mRNA between the two strains at either age. The intensity and localization of the hybridization signal for NOS-III mRNA in the heart of SHR-SP/Izm did not differ from those in the heart of WKY/Izm. These results suggest that the attenuated biological action of NO implied in genetically hypertensive rats is not attributed to an abnormality at the level of NOS-III mRNA expression in the tissues, although lack of an increase in NOS-III gene expression, despite the hypertensive hemodynamic stress, may modify the blood pressure in hypertension.

Oncostatin M: a new potent inhibitor of iodine metabolism inhibits thyroid peroxidase gene expression but not DNA synthesis in porcine thyroid cells in culture

The functions of thyroid cells are regulated by a number of cytokines and growth factors in addition to TSH. Recent studies have revealed that several cytokines including interleukin (IL)-6 are involved in thyroid dysfunction. Oncostatin M (OSM) is a glycoprotein belonging to the same family of cytokines as IL-6, to which it is related by sequence and structural homology and the use of the signal-transducing receptor component gp130. We, therefore, studied the effect of OSM on iodide uptake and DNA synthesis by porcine thyroid cells in culture. OSM increased c-fos and c-jun mRNA levels but did not stimulate DNA synthesis. OSM inhibited iodide uptake stimulated by TSH; while IL-6 also inhibited iodide uptake, it was only about one-tenth as potent. IL-6 had about the same potency as OSM when it was added with soluble IL-6 receptor. OSM had no effect on cAMP production but inhibited iodide uptake stimulated by 8-bromo-cAMP and forskolin. These findings suggest that OSM exerts its inhibitory effects at the post-cAMP production step(s). OSM also inhibited thyroid peroxidase mRNA levels but had little effect on thyroglobulin mRNA levels. Investigations of the signal transduction system showed that gp130 and leukemia inhibitory factor (LIF) receptor beta subunit mRNA were detectable in porcine thyroid cells by reverse transcription (RT)-polymerase chain reaction (PCR). Together with the report that serum OSM and IL-6 concentrations are elevated to the same levels in patients with sepsis, these results suggest that OSM may contribute to the thyroid dysfunction in this condition.

Different expression of immediate-early genes in the rat paraventricular nucleus induced by stress: relation to corticotropin-releasing factor gene transcription

Stressful stimuli induce the transcriptional activation of the corticotropin-releasing factor (CRF) gene as well as that of various immediate-early genes (IEGs). Among them, members of the fos/jun families play an important role in the regulation of gene expression. The possible relation between stress-induced IEG expression and CRF gene transcription was investigated by analysis of stress-induced changes in the abundance of c-fos, c-jun, jun-B, jun-D, and NGFI-B mRNA as well as CRF heteronuclear RNA (hnRNA), which reflects gene transcription, in the rat paraventricular nucleus (PVN) by in situ hybridization. Restraint stress induced rapid (within 5 min) and transient increases in the level of c-fos mRNA and CRF hnRNA in the PVN, with peak expression apparent 30 min after the onset of stress. The induction of jun-B and NGFI-B gene expression was also rapid and transient, but was delayed relative to that of c-fos mRNA and the CRF hnRNA. In contrast, both jun-D and c-jun were constitutively expressed in the PVN, and the amount of the corresponding transcripts increased only slightly in response to stress. These results reveal differential patterns of expression of IEGs in the PVN in response to stress. The observation that the level of mRNAs corresponding to these IEGs did not increase before that of CRF hnRNA may suggest that the products of these genes do not seem to directly mediate the stress-induced increase in CRF gene transcription in the PVN.

Carboxy-terminal propeptide of type 1 procollagen (P1CP) and carboxy-terminal telopeptide of type 1 collagen (1CTP) as sensitive markers of bone metabolism in thyroid disease

We measured serum levels of the carboxy-terminal propeptide of type 1 procollagen (P1CP) as a marker of bone formation and the carboxy-terminal telopeptide of type 1 collagen (1CTP) as a marker of bone resorption by RIA in sera from 40 Graves' disease patients and 14 Hashimoto's disease patients before and during treatment. The serum P1CP levels of the untreated Graves' disease were significantly higher than in the controls (176.8 +/- 93.5 vs. 107 +/- 35 ng/ml, P < 0.01), and these levels decreased significantly during treatment with antithyroid drugs. There was a significant statistical correlation between serum P1CP levels and serum total alkaline-phosphatase activity (r = 0.61, P < 0.01) in the patients with Graves' disease and Hashimoto's disease as a whole. 1CTP levels were also significantly increased in untreated Graves' patients (6.5 +/- 2.8 compared with 2.7 +/- 1.1 ng/ml in normal subjects, P < 0.01). The P1CP/1CTP ratio, which reflects the relative ratio of bone formation to bone resorption, was lower than normal in untreated Graves' disease, but increased following the normalization of thyroid function. The results of this study suggest that the measurement of serum P1CP and 1CTP levels may be useful in evaluating bone metabolism in thyroid disease.

Vascular action of circulating and local natriuretic peptide systems is potentiated in obese/hyperglycemic and hypertensive rats

Hypertension is commonly associated with diabetes mellitus. The aim of the present study was to explore the pathophysiological significance of the natriuretic peptide (NP) system in hypertension associated with genetically obese/hyperglycemic Wistar fatty rats. The messenger RNA (mRNA) levels of the two biologically active NP receptors, NP-A receptor [more specific for atrial natriuretic peptide (ANP)] and NP-B receptor [more specific for C-type natriuretic peptide (CNP)], and CNP mRNA levels were determined in the aorta and kidney by ribonuclease protection assay. Plasma ANP levels were determined by RIA. Both NP-A and NP-B receptor mRNA levels in the aortae of Wistar fatty rats were double those in Wistar lean rats. Plasma ANP levels and CNP mRNA levels in the aorta of Wistar fatty rats were also significantly higher than those in Wistar lean rats. In contrast, there was no significant difference in renal levels of the mRNA for both NP receptors and CNP between the two strains. Administration of a NP-A and -B receptor antagonist, HS-142-1, to Wistar fatty rats resulted in a significant increase in systolic blood pressure and a larger decrease in plasma cGMP level than that in Wistar lean rats, with no difference in the extents of decrease in urine volume and urinary sodium excretion between the two strains. These results suggest that both the ANP/NP-A system and the CNP/NP-B system in vessels are up-regulated at the level of gene expression and may, thus, play an important role in counteracting the hypertension associated with diabetes mellitus.

Acutely exacerbated hypertension and increased inflammatory signs due to radiation treatment for metastatic pheochromocytoma

Hypertension and norepinephrine hypersecretion in a 59-year-old woman suffering from malignant pheochromocytoma with multiple metastases were appropriately controlled with alpha- and beta- blockers, and alpha-methyltyrosine (alpha-MT), a catecholamine-synthesis inhibitor. Metastasized vertebrae were treated with external radiation to relieve pain, but this treatment had to be interrupted at a total dose of 20 Gy because the patient suffered acutely exacerbated hypertension (200/110 mmHg), tachycardia (160 beats/min) and a low-grade fever. Simultaneously her serum levels of LDH, potassium, urea nitrogen, creatinine, white blood cell count, CRP and norepinephrine were significantly increased, suggesting that this episode was due to radiation-induced tissue destruction and the leakage of catecholamines and possibly interleukin-6, a cytokine mediating inflammation which is reportedly present in pheochromocytoma. The marked hypertension was controlled by continuous i.v. administration of phentolamine and propranolol. Although radiation therapy effectively relieves pain due to neoplasmic metastasis to the bone, physicians should be aware that life-threatening complications such as the above occur in malignant pheochromocytoma. Sufficient pretreatment with adrenergic blocking agents and/or alpha-MT and careful monitoring of the patient's general condition during radiation therapy, even at a low dose, are highly recommended.