The effects of central administration of angiotensin II type-1 receptor antagonist, CV-11974, in nephrectomized spontaneously hypertensive rats

1. The role of the brain renin-angiotensin system in the pathogenesis of genetic hypertension was evaluated using a specific non-peptide angiotensin II type-1 receptor antagonist, TCV-116. 2. CV-11974 (active metabolite of TCV-116) was acutely injected either intravenously (i.v.) or intracerebroventricularly (i.c.v) in male spontaneously hypertensive rats (SHR; 12 week old). In separate groups of nephrectomized and sham-operated SHR, graded doses of CV-11974 were administered either i.v. or i.c.v. for 2 days using an osmotic minipump. In another group, the effects of nephrectomy on the depressor effect of chronic treatment with CV-11974 were investigated. Haemodynamics at three points: before infusion, before nephrectomy and 48 h after nephrectomy, were monitored. 3. Acute i.c.v. injection of CV-11974 decreased blood pressure in the presence of the kidney. Prolonged i.c.v. administration of the drug for 2 days decreased blood pressure even at the lowest dosage, which had no hypotensive effects when given i.v. The hypotensive effect of centrally administered CV-11974 was noted even 48 h after bilateral nephrectomy. 4. These results suggest that the brain renin-angiotensin system has a primary role in the maintenance of hypertension after eliminating the circulating renin-angiotensin system in SHR.

[Risk factors related to the wall thickness of carotid artery assessed by ultrasonography]

Progression of atherosclerotic lesion of the carotid artery is suggested to induce the development of cerebrovascular events. We evaluate the risk factors related to carotid artery, wall thickness by ultrasonography. A total of 159 patients, who had received no medication for hypertension or hyperlipidemia were enrolled in this study. The wall thickness of carotid artery was evaluated as an intima-media (IM) complex measured by B-mode ultrasonography with a 7.5 MHz probe. Simple regression analysis demonstrated significant correlation between the IM complex and both age and systolic blood pressure, but not with fasting levels of plasma glucose, hemoglobin A1c, total and HDL cholesterol, triglyceride or gender. Stepwise regression analysis showed age and systolic blood pressure contribute to IM thickness (r = 0.623). However, in patients aged 60 or over, blood pressure did not contribute to the IM wall thickness. Smoking was not a risk factor for IM thickness, but the Brinkman Index (daily consumption of cigarettes x years smoking) was significantly higher in patients with plaques in the carotid artery than those without it. These results suggest that high blood pressure is a risk factor for mild atherosclerotic lesions of the carotid artery for those aged under 60. Smoking may contribute to the formation of plaque, which may consequently lead to the ischemic cerebrovascular disease.

[Effects of pravastatin administration for 12 months on serum lipid levels in aged patients with hypercholesterolemia]

To evaluate long-term efficacy of pravastatin, we administered this HMG-CoA reductase inhibitor at a mean dose of 9.9 mg/day to 208 aged patients with serum levels of total cholesterol (TC) over 220 mg/dl (mean +/- SD aged of 70 +/- 7 years; 62 males and 146 females) for 12 months. The mean serum value of TC significantly decreased from the basal level of 265 mg/dl to 216 mg/dl in the 3rd month, and this decrease was maintained throughout the observation period. Similar change was observed in the serum level of low density lipoprotein-cholesterol (LDL-C). Although the mean serum level of high density lipoprotein-cholesterol (HLC-C) in all patients did not change significantly, the HDL-C level in 34 patients with a HDL-C level below 40 mg/dl significantly increased from the 3rd month. The mean serum level of triglyceride (TG) in all patients significantly decreased from the 3rd month, and this decrease in the TG was more prominent in 101 aged patients with TG levels higher than 150 mg/dl. In 168 aged patients on 10 mg/day of pravastatin throughout the period, there were significant negative correlations between the ratio of the decrease in TC in basal serum and each of the basal serum TC levels (r = -0.345, p < 0.001) and age of the subjects (r = -0.208, p = 0.007). These results indicate that long-term administration of pravastatin is effective treatment for lipid metabolism even in aged patients.

Long-term therapy with terazosin may improve glucose and lipid metabolism in hypertensives: a multicenter prospective study

The effects of long-term monotherapy with terazosin, an alpha-1 blocker, on blood pressure, glucose tolerance, and serum lipid profiles were prospectively investigated in 53 hypertensive patients: 19 with normal glucose tolerance (NGT) and 34 with impaired glucose tolerance (IGT). The plasma glucose, serum lipids, fructosamine, and glycosylated hemoglobin A1c (HbA1c) levels were determined before and during long-term (6 months) therapy with terazosin. A 75-g oral glucose tolerance test was performed before and during long-term terazosin therapy. Significant falls in both systolic and diastolic blood pressure in both patient groups were maintained during the long-term therapy with terazosin. Neither fasting nor postglucose-load venous plasma glucose levels were altered in either group of patients, and diabetes mellitus did not develop in any patient with NGT during the study. There was no significant change in the insulinogenic index (delta IRI/delta BS at 30 minutes after glucose load) in either patient group. In patients with IGT, glucose intolerance was slightly improved with significant reductions in HbA1c and fructosamine during terazosin therapy. Serum total cholesterol (TC) and triglyceride levels were significantly decreased in patients with IGT. In addition, TC and low density lipoprotein (LDL) cholesterol were significantly decreased in patients with hypercholesterolemia (TC > 220 mg/dL). These results suggest that long-term therapy with terazosin may improve glucose and lipid metabolism in hypertensive patients and terazosin seems to be an antihypertensive agent with beneficial effects for hypertensive patients with either dyslipidemia or impaired glucose metabolism.

Effects of the angiotensin II receptor antagonist, TCV-116, on blood pressure and the renin-angiotensin system in healthy subjects

TCV-116 is a new, nonpeptide, angiotensin II type-1 receptor antagonist that acts as a specific inhibitor of the renin-angiotensin system. In this study, 36 healthy male volunteers were administered single and repeated oral doses of TCV-116 to investigate its effects on blood pressure and heart rate, and to evaluate the safety and pharmacokinetics of the drug. At single doses of 2.5 mg and greater, TCV-116 significantly lowered blood pressure even in normotensive subjects. This hypotensive effect was maintained during repeated administration on a once-daily regimen over an 8-day period. Serum concentration of M-1, an active metabolite of TCV-116, increased in a dose-dependent manner, reaching a peak 3 to 4 hours after administration. An amount of M-1 equivalent to approximately 10% of the administered dose of TCV-116 was excreted in the urine during the first 24 hours following administration. No accumulation of M-1 was observed in subjects receiving repeated administration of TCV-116. No adverse effects were observed except for mild headache in three subjects. These results suggest that the renin-angiotensin system plays a role in the regulation of blood pressure, even in normotensive subjects, and that TCV-116 may prove to be useful in the treatment of hypertension.

Role of the renin-angiotensin system in hypertension in the elderly

Although the activity of the renin-angiotensin system is known to decrease with age, the antihypertensive efficacy of angiotensin-converting enzyme (ACE) inhibitors has been demonstrated in the elderly. To examine the role of the renin-angiotensin system in hypertension in the elderly, we evaluated the antihypertensive response to enalapril and to TCV-116, an angiotensin II type-1 receptor antagonist, in elderly patients with essential hypertension. A single oral dose of enalapril (10 mg) increased plasma renin activity (PRA) and reduced the angiotensin II concentration, whereas a single oral dose of TCV-116 (4 mg) increased both PRA and the angiotensin II concentration. Blood pressure was significantly reduced by these drugs from 4 h after administration. Basal levels of PRA and angiotensin II declined with age. However, the changes in blood pressure produced by either TCV-116 or enalapril did not correlate with age. These results suggest that the activity of the renin-angiotensin system in plasma declines with age, and that the extrarenal renin-angiotensin system may play a role in hypertension in the elderly.

Effects of age and hypertension on autonomic nervous regulation during passive head-up tilt

To study the effects of age and hypertension on autonomic nervous function with passive postural change, we examined 31 normotensive subjects (25 to 85 years old) and 31 hypertensive patients (21 to 71 years old) without any cardiac disease, diabetes mellitus, or neurological disorders. Subjects were passively placed in a 60 degrees head-up tilting position after 15 minutes in the supine position. Autonomic nervous function was evaluated by frequency domain analysis of heart rate with the autoregressive method. Using low-frequency (0.1 Hz) and high-frequency (0.25 Hz) peaks, the ratio of low- to high-frequency power (L/H) was calculated as an index of sympathetic activity and the ratio of high to total power (%HF) as that of parasympathetic activity. With the patient in the supine position, total power spectral density declined logarithmically with age in normotensive subjects and hypertensive patients, but %HF and L/H showed no changes. In response to passive tilting, L/H was increased and %HF was decreased in the normotensive subjects, and these responses declined with age logarithmically. In contrast, hypertensive patients exhibited less autonomic response to postural change regardless of age. These results suggest that autonomic neural response to tilt is decreased with age; however, attenuation of the response by hypertension is not associated with an increase in age.

Immunoreactivity to M2 proteins in antimitochondrial antibody-negative patients with primary biliary cirrhosis

Although antimitochondrial auto-antibodies are characteristically present in the serum of patients with primary biliary cirrhosis (PBC), there is a discrepancy between the positivity for antimitochondrial antibody (AMA) and that for anti-M2 auto-antibody. In an attempt to explain the discrepancy, this study investigates the relationship between the AMA titre, determined by indirect immunofluorescence, and immunoreactivity to four inner mitochondrial membrane proteins (M2 proteins) with molecular weights of 70, 50, 47, and 40 kDa in 129 patients with PBC. Antimitochondrial antibody positivity was identified in 114 (88%) of 129 patients with clinically and histologically confirmed PBC. There were no significant differences between the AMA-negative and AMA-positive groups in clinical characteristics or histologically determined disease stage. Immunoblot analysis showed that all patients had anti-M2 auto-antibodies to one or more of the four M2 proteins. Nine (60%) of the 15 AMA-negative patients had antibodies to only one M2 protein (either 70 or 47 kDa). In contrast, 34 (53%) of the 64 patients with high AMA titres (> or = 1:320) had antibodies to all four M2 proteins. There was a significant rank correlation between the AMA titre and the number of antibodies to M2 proteins (P < 0.01). These findings indicate that the AMA titre is not influenced by the immunogenicity of M2 proteins but by the number of M2 proteins that elicit an antibody response and that decreased immunoreactivity to M2 proteins may induce AMA negativity in PBC serum samples.

Estimation of time of death by quantification of melatonin in corpses

A method for the estimation of time of death (TOD), was evaluated by measuring the melatonin (MT) content of pineal bodies (PBs), sera and urine samples from 85 cadavers. A total of 44 cadavers were investigated in Sapporo (geographical coordinates N 43 degrees 4', E 141 degrees 21') and 41 in Tokyo (N 35 degrees 39', E 139 degrees 44'). MT contents were measured by radioimmunoassay (RIA) in 75 PBs, 27 sera and 14 urine samples. Exponential differences of pineal MT content were recognized between peaks in nighttime and nadirs in daytime, ranging from 0.099 to 63.2 ng/PB. Circadian rhythms were also observed for the concentrations of MT in serum (11-205 pg/ml), and in urine (7.5-137.5 pg/ml). Consequently, criteria for the TOD estimation are proposed as follows. 1) Pineal MT contents--(1) 0-0.2 ng/PB: TOD 1100-1700 hours, (2) 0.2-0.3 ng/PB: TOD 0700-2000 hours, (3) 0.3-1 ng/PB: inconclusive, (4) 1-4 ng/PB: TOD 1600-1000 hours, (5) 4-8 ng/PB: TOD 2000-0800 hours, (6) over 8 ng/PB: TOD 2000-0500 hours, 2) Serum MT concentration--(1) 0-100 pg/ml: inconclusive, (2) over 100 pg/ml: TOD 2200-0100 hours, and 3) Urinary MT concentration--(1) 0-35 pg/ml: inconclusive, (2) over 35 pg/ml: TOD 1800-0600 hours. The range of the estimation can be limited by a combination of these 3 criteria. The present method can be combined with other methods for estimating the TOD to decrease the range.

The role of activated vascular angiotensin II generation in vascular hypertrophy in one-kidney, one clip hypertensive rats

OBJECTIVE

To investigate the role of vascular angiotensin II (Ang II) in the vascular thickening of one-kidney, one clip (1-K, 1C) hypertensive rats, which show normal plasma renin activity.

METHODS

The type 1 Ang II receptor antagonist TCV-116 (1 mg/kg per day), the angiotensin converting enzyme (ACE) inhibitor delapril (20 mg/kg per day), hydralazine (20 mg/kg per day) or vehicle were administered to four groups of 1-K, 1C rats aged 6-10 weeks. Vehicle was also given to uninephrectomized rats.

RESULTS

The aortae of 1-K, 1C rats contained significantly higher levels of Ang II than those of uninephrectomized rats and showed hypertrophy, but not hyperplasia of their medial smooth muscle cells. Hypertrophy was estimated by immunohistochemical staining of alpha-actin. Hyperplasia was estimated by DNA content and incorporation of 5-bromo-2'-deoxyuridine. The blood pressure of the 1-K, 1C rats was not affected by either TCV-116 or delapril, even at doses sufficient to induce depressor effects in spontaneously hypertensive rats. However, subdepressor doses of TCV-116 and delapril both significantly reduced the alpha-actin-stained area to 78 and 73%, respectively, of that in the 1-K, 1C rats, whereas a depressor dose of hydralazine did not affect the alpha-actin-stained area. The level of Ang II in the aorta, but not in plasma, was suppressed by delapril but not by hydralazine.

CONCLUSIONS

These results suggest strongly that vascular Ang II plays a major role in the development of vascular hypertrophy, independently of plasma Ang II, bradykinin and ACE-independent pathways of Ang II generation, and in the regulation of blood pressure in this normoreninaemic hypertensive model.

Hypertensive rats produced by in vivo introduction of the human renin gene

We established an efficient and nontoxic in vivo gene transfer method mediated by the Sendai virus (hemagglutinating virus of Japan [HVJ]), liposomes, and nuclear protein. In this study, to produce a hypertensive model rat that is dependent on human renin, the human renin gene was introduced into adult rat liver by our efficient in vivo gene transfer method using HVJ and liposomes (HVJ-liposomes). The rats treated with HVJ-liposomes containing the human renin gene showed a significant elevation of blood pressure for 6 days compared with control rats, which received injections of HVJ-liposomes without the human renin gene. On day 5 after the transfer, human active renin as well as angiotensin II were found in the plasma of rats in which the human renin gene was introduced. Moreover, the blood pressure of these rats was significantly correlated with the plasma levels of human active renin and angiotensin II. To confirm that the elevated blood pressure was due to the expression of the human renin gene, we administered a newly developed specific human renin inhibitor, FK 906. The elevated blood pressure was normalized by the intravenous administration of this drug. These data indicate that this hypertensive rat was produced by the in vivo transfer of the human renin gene into rat liver and that the expressed human renin cleaved rat substrate (angiotensinogen). This hypertensive rat produced by in vivo gene transfer should be useful in further studies on hypertension.

Pilot study of a new angiotensin II receptor antagonist, TCV-116: effects of a single oral dose on blood pressure in patients with essential hypertension

After a 1-week placebo control period, six hypertensive patients (mean age, 67 years) each received single doses of 1, 2.5, and 5 mg of TCV-116 at 2- to 3- day intervals. Systolic and diastolic blood pressures were significantly lower after the final dose (5 mg) of TCV-116 than on the last day of the placebo period. Blood pressures were decreased after each dose of TCV-116 in a dose-dependent fashion from 2 hours after administration and reached a nadir at 4 to 6 hours. After 2.5 and 5 mg of TCV-116, the hypotensive effect was sustained for 24 hours. Pulse rate did not change significantly. Plasma renin activity and angiotensin I levels increased in a dose-dependent fashion after TCV-116, but the changes were not significant. No changes were noted in plasma aldosterone or angiotensin II levels. One patient reported mild light-headedness after 5 mg of TCV-116. No other side effects or abnormal laboratory tests results were noted. It appears that TCV-116 is a safe and effective antihypertensive agent.

Angiotensin blockade and the progression of renal damage in the spontaneously hypertensive rat

The pathophysiological role of angiotensin II in the development of renal sclerosis was investigated in 5/6-nephrectomized, 12-week-old male spontaneously hypertensive rats. After 1 week of a control period, nephrectomized rats received one of the following treatments for 4 weeks: the selective nonpeptide angiotensin II type 1 receptor antagonist TCV-116 (1 mg/kg per day), the angiotensin converting enzyme inhibitor delapril (30 mg/kg per day), hydralazine (15 mg/kg per day), or vehicle. Urinary protein and albumin excretions and systolic blood pressure were determined every week. Rats with reduced renal mass treated with vehicle had a poor survival rate (30%). Although TCV-116, delapril, and hydralazine treatment significantly improved the survival rate for 4 weeks, hydralazine failed to improve proteinuria and albuminuria as well as the decline in renal function compared with delapril or TCV-116. Histological examination revealed that both TCV-116 and delapril protected glomeruli from sclerosis, whereas hydralazine did not improve histological findings (5%, 7%, and 30% of glomeruli were affected, respectively). These results indicate that angiotensin II plays a dominant role through its type 1 receptor in the pathogenesis of renal deterioration by hypertension.

Role of angiotensin II in high fructose-induced left ventricular hypertrophy in rats

Recent studies suggest the linkage of hypertension and insulin resistance. High fructose diet is known to induce hyperinsulinemia and hypertension in rats. In a previous study, however, high fructose (66%) diet failed to elevate blood pressure but increased left ventricular weight in Sprague-Dawley rats. In the present study, we investigated the precise mechanism of high fructose diet-induced changes in the cardiovascular system in rats. Intake of fructose-enriched diet for 2 weeks increased serum insulin and plasma angiotensin II levels. Urinary excretion of sodium and norepinephrine was not changed. Blood pressure measured directly through an indwelling catheter was not increased, but left ventricular weight and protein content were increased by high fructose diet. To further elucidate the role of the renin-angiotensin system, an angiotensin II type 1 receptor antagonist, TCV-116, was given orally at 1 mg/kg per day with either normal or high fructose diet. Concomitant administration of TCV-116 did not affect plasma glucose or serum insulin levels. Plasma angiotensin II was increased, but neither urinary sodium nor norepinephrine was changed by TCV-116. TCV-116 similarly decreased blood pressure in rats on normal and high fructose diets. Increase in left ventricular weight induced by high fructose diet was prevented by the concomitant administration of TCV-116. On the other hand, left ventricular weight in control rats was not changed by TCV-116. In conclusion, increased plasma angiotensin II may account for the left ventricular hypertrophy induced by high fructose diet, whereas hemodynamic change, sodium retention, and the sympathetic nervous system do not play an important role.

[Estimation of death time by measurement of circadian melatonin rhythm]

In order to establish a method for the estimation of death time (DT) from measuring melatonin (MT) contents in pineal bodies (PBs) and biological fluids, 85 cadavers were investigated--44 dead in Sapporo (N 43 degrees 4', E 141 degrees 21') and 41 in Tokyo (N 35 degrees 39', E 139 degrees 44'). MT contents were measured by radioimmunoassay in 76 PBs, 27 sera and 14 urines. Exponential differences were recognized between peaks in nighttime and nadirs in daytime of pineal MT contents, i. e., ranging 0.099-63.158 ng per PB and 1.2-609.6 pg/mg. Circadian rhythms were also observed on the concentrations of MT in serum (11-205 pg/ml), and in urine (7.5-137.5 pg/ml). Consequently, criteria of the DT estimation were proposed as follows. 1) Pineal MT contents--(1) 0-0.2 ng/PB:DT 11:00-17:00, (2) 0.2-0.3 ng/PB:DT 7:00-20:00, (3) 0.3-1 ng/PB: incapable of DT estimation, (4) 1-4 ng/PB:DT 16:00-10:00, (5) 4-8 ng/PB:DT 20:00-8:00, (6) 8 ng/PB over: DT 20:00-5:00, 2) Serum MT concentration--(1) 0-100 pg/ml: incapable of DT estimation, (2) 100pg/ml over: DT 22:00-1:00, and 3) Urinary MT concentration--(1) 0-35pg/ml: incapable of DT estimation, (2) 35 g/ml over: DT 18:00-6:00. Furthermore, width of the estimation is able to be narrowed by the combination of these three criteria. The present method is very useful in narrowing the width of DT estimation which has been usually carried out by observing the progress of cadaveric phenomena on and in dead bodies.

Antihypertensive efficacy of FK906, a novel human renin inhibitor

The antihypertensive efficacy of a newly developed orally active human renin inhibitor (FK906) was evaluated in 14 patients with essential hypertension aged 40 to 83 years (mean, 64 years). After a 1-week placebo run-in period, 25 mg of FK906 was given twice daily; this was increased up to 100 mg twice daily until sufficient blood pressure reduction was obtained. No adverse effects were observed in any patients. Supine blood pressure was decreased from 169 +/- 3/97 +/- 1 mmHg to 153 +/- 5/87 +/- 3 mmHg at 25 mg twice daily (n = 14), to 142 +/- 5/78 +/- 3 mmHg at 50 mg twice daily (n = 12), P < 0.01), and to 137 +/- 10/77 +/- 8 mmHg at 100 mg twice daily (n = 6, P < 0.01). The hypotensive effect was sustained over 24 hours. Pulse rate did not change. Plasma renin activity and angiotensin I were decreased after FK906 administration only in patients with increased plasma renin activity. The hypotensive effects of FK906 were not correlated with baseline plasma renin activity. Suppression of the noncirculating tissue renin-angiotensin system may account for the hypotensive action of FK906. The results suggest that FK906 is a promising antihypertensive drug in patients of all ages and with different plasma renin levels.

Dahl's salt-resistant normotensive rat has mutations in cytochrome P450(11 beta), but the salt-sensitive hypertensive rat does not

Molecular cloning of cytochrome P450(11 beta) cDNAs from the adrenal glands of Dahl's salt-sensitive hypertensive (DS) and salt-resistant normotensive (DR) rats was performed using a combined technique of the first strand cDNA synthesis by reverse transcriptase followed by polymerase chain reaction. The cDNA sequence of P450(11 beta)-DS was identical to that of wild type P450(11 beta). In contrast, the clone obtained from the DR rat contained six nucleotide substitutions causing five amino acid alterations (Arg-127-->Cys, Val-351-->Ala, Val-381-->Leu, Ile-384-->Leu, and Val-443-->Met). When the two cDNAs were expressed in COS-7 cells and steroid conversion rates of the transformed cells were determined, a ratio of 18-hydroxylation to 11 beta-hydroxylation of 11-deoxycorticosterone by P450(11 beta)-DS-expressed cells was 0.58, whereas that by P450(11 beta)-DR-expressed cells was 0.23. Plasma levels of 18-hydroxy-11-deoxycorticosterone and corticosterone (the 11 beta-hydroxylation product of 11-deoxycorticosterone) in DS and DR rats well reflected the steroidogenic activities of the two P450s. These results suggest that the characteristic plasma steroid level of the DR rat is caused by the mutations in P450(11 beta) gene and may act to maintain the normotensive blood pressure in this rat strain during sodium loading.

A neuropeptide Y locus on chromosome 4 cosegregates with blood pressure in the spontaneously hypertensive rat

Recent advances in molecular biology have allowed the study of the candidate genes for essential hypertension. To identify the genes responsible for basal blood pressure in the spontaneously hypertensive rat strain, the rat model of genetic hypertension, we performed a cosegregation analysis between the genotype and blood pressure in a set of male F2 progeny obtained from SHR and Wistar-Kyoto rats, a reference normotensive strain. Our investigation revealed that a locus on the chromosome 4 cosegregates with the blood pressure in SHR, especially at neuropeptide Y locus. The degree of cosegregation with all values of blood pressure without sodium loading was moderate but consistent. We propose that neuropeptide Y locus on chromosome 4 is a new candidate for the hypertensive effect in original SHR.

Association analysis of a polymorphism of the angiotensin converting enzyme gene with essential hypertension in the Japanese population

An association study of the insertion/deletion (I/D) polymorphism located in intron 16 of the ACE gene with essential hypertension in the Japanese population was performed. The 287 bp I/D polymorphism was detected by polymerase chain reaction. Derived allele frequencies for insertion and deletion were not significantly different between 133 hypertensive and 104 normotensive subjects. A significant relationship between I/D polymorphism and plasma ACE activity was observed in the normotensive group, but not in hypertensives. These results suggest that I/D polymorphism of the gene is not implicated in Japanese hypertensive subjects, and that studies involving various ethnic groups are important.

Evaluation of orthostatic hypotension using power spectral analysis

To evaluate the pathogenesis of orthostatic hypotension, we studied the autonomic regulation system by measuring heart rate variability during 60 degrees passive head-up tilt using power spectral analysis in 21 patients with orthostatic hypotension (mean age 62 +/- 2 years, five with histories of cerebrovascular accidents, five with Parkinsonism, five with diabetes mellitus, three with pheochromocytoma, and three with unknown causes) and 15 normal healthy subjects as a control (mean age 63 +/- 2 years). We also assessed plasma epinephrine and norepinephrine response to tilt. During tilt, control subjects showed an increase in heart rate with no change in blood pressure. Spectral analysis of heart rate variability demonstrated increases in the low frequency band (LFB, mainly sympathetic) and low frequency band/high frequency band ratio (LFB/HFB, sympatho-vagal balance). All patients with orthostatic hypotension showed a significant reduction in blood pressure with an increase in heart rate. In patients with histories of cerebrovascular accidents and with Parkinsonism, LFB and the LFB/HFB ratio did not increase. However, in other patients with orthostatic hypotension, LFB and the LFB/HFB ratio increased during tilt. Norepinephrine increased in control subjects and in patients with diabetes mellitus, pheochromocytoma, and unknown causes. In contrast, patients with histories of cerebrovascular accidents and patients with Parkinsonism showed no increase in norepinephrine. Epinephrine responses paralleled those of norepinephrine, but the changes were not significant. Thus, neurological response to tilt is not uniform in patients with orthostatic hypotension. Patients with histories of cerebrovascular accidents and patients with Parkinsonism may have impaired function of central neural mechanisms controlling blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of tissue renin angiotensin system in two-kidney, one-clip hypertensive rats

To investigate the molecular pathology of two-kidney, one-clip (2K-1C) rats, we examined the gene expressions of the renin-angiotensin system (RAS) and angiotensin II (ANG II) concentration in various tissues in the early (4 wk) and chronic (16 wk) phases of hypertension. Four weeks after clipping, the brain renin mRNA level was lower in 2K-1C rats than in control rats (P < 0.05). On the other hand, the levels of brain and renal angiotensinogen mRNA were not significantly different in the two groups. The brain and adrenal ANG II concentrations were significantly higher in 2K-1C rats than in control rats. Sixteen weeks after clipping, there was no significant difference in the brain renin mRNA levels in the two groups, and renal and brain angiotensinogen mRNA levels were normal. Moreover, the ANG II concentrations in the adrenals and brain (except the cortex) of 2K-1C rats were not significantly higher than those in control rats. These results show a differential pattern of tissue RAS gene expression in rats during the development of 2K-1C hypertension, which is regulated in a tissue-specific manner. Furthermore, the data suggest that brain ANG II may be affected by circulating ANG II, but not by the brain renin angiotensin system, and may regulate brain renin, probably by negative feedback through its own receptor.

The angiotensin-converting enzyme inhibitor, perindopril, prevents cardiac hypertrophy in low-renin hypertensive rats

1. To examine whether an angiotensin-converting enzyme (ACE) inhibitor prevents left ventricular (LV) hypertrophy even in low-renin hypertension, we studied the effect of the administration of perindopril on cardiac hypertrophy induced by partial renal ablation in hypertensive rats. 2. Rats that had undergone partial nephrectomy were randomly divided into four groups that received the following as drinking water: Group A, tap water; Group B, 1% sodium chloride (NaCl); Group C, NaCl + perindopril 3 mg/kg per day; and Group D, NaCl + perindopril 1 mg/kg per day. Plasma renin activity (PRA), angiotensin-II (AII) concentration and cardiac tissue AII were measured. 3. Supplementation of NaCl following nephrectomy increased the blood pressure and cardiac weight compared with rats that had undergone nephrectomy alone (P < 0.05). Treatment with perindopril (3 mg/kg per day) did not affect the blood pressure and plasma AII but inhibited the increase of cardiac weight (P < 0.05). Left ventricular AII was decreased in cases of reduced renal mass hypertension, but was not changed by treatment with perindopril. 4. These results demonstrate that perindopril may be able to prevent LV hypertrophy even in low-renin hypertension, which was not mediated by a reduction of blood pressure or suppression of the circulating and cardiac renin-angiotensin systems. Other mechanisms of ACE inhibitors may contribute to the cardioprotective effects.