Renin, angiotensin and aldosterone system in pathogenesis and management of hypertensive vascular disease

Association of the renin-sodium profile with the risk of myocardial infarction in patients with hypertension

BACKGROUND

To test the prognostic value of plasma renin activity prospectively, we determined the pretreatment renin-sodium profile of 1717 subjects with mild-to-moderate hypertension (mean age, 53 years; 36 percent white; 67 percent men) in a systematic work-site treatment program.

METHODS

Renin profiles, obtained by plotting plasma renin activity against the urinary excretion of sodium, were classified as high (12 percent of the subjects), normal (56 percent), and low (32 percent), and there were expected variations according to age, sex, and race. Modified stepped-care treatment for hypertension, prescribed without reference to the renin profile, was similar in the three renin groups.

RESULTS

Mean (+/- SD) blood pressure at entry was 151 +/- 19/100 +/- 10 mm Hg in the subjects with a high renin profile, 151 +/- 19/97 +/- 10 mm Hg in those with a normal profile, and 151 +/- 20/96 +/- 11 mm Hg in those with a low profile. During 8.3 years of follow-up, there were 27 myocardial infarctions. As adjusted for age, sex, and race, the incidence of myocardial infarction per 1000 person-years was 14.7 among the subjects with a high renin profile, 5.6 among those with a normal profile, and 2.8 among those with a low profile (rate ratio for high vs. low, 5.3; 95 percent confidence interval, 3.4 to 8.3). The rate of mortality from all causes was 9.3 in the high-profile group, 5.3 in the normal-profile group, and 3.9 in the low-profile group. The independent association of a high renin profile with myocardial infarction (but not with stroke or noncardiovascular events) was affirmed by Cox analyses (rate ratio for high vs. normal plus low, 3.2; 95 percent confidence interval, 1.2 to 8.4) after adjustment for race, sex, age at entry, serum cholesterol level, smoking status, electrocardiographic evidence of left ventricular hypertrophy, blood glucose level, body-mass index, history of cardiovascular disease or treatment, blood pressure, and use of beta-blockers.

CONCLUSIONS

In the study population, whose blood pressure before and during treatment was in a narrow range, and after other cardiovascular risk factors had been considered, the renin profile before treatment remained independently associated with the subsequent risk of myocardial infarction.

Interventions in renal scintigraphy

Physiological and pharmacological intervention for the purpose of determining organ functional reserve is a familiar concept in medical testing and in nuclear medicine. Nephrourologic applications include established procedures such as diuretic scintigraphy for determination of urinary outflow obstruction and captopril scintigraphy for determination of renovascular hypertension. Subtle renal dysfunction may exist among some individuals with essential hypertension, induced by provocative exercise renography, and not observed at rest. The strength of nuclear medicine resides in its ability to assess disorders of organ function for the diagnostic, prognostic, or pathophysiological information provided. Nephrourologic interventions are reviewed with an emphasis on the functional changes caused by the intervention.

Donor gender does not affect liver transplantation outcome in children

The liver is recognized as a sex hormone-responsive organ. Gender-specific differences in liver function are known to exist. Recently, a higher failure rate for organs transplanted in adults from female donors to male recipients has been reported. This increased failure rate of livers obtained from adult females and transplanted into adult males is thought to occur, at least in part, as a result of intrinsic gender-specific differences in hepatocyte cell surface expression and to alterations in the hormonal milieu of the donor liver in the recipient. To determine whether the same graft-recipient gender-determined failure rates pertain in the pediatric liver transplant population, the outcome of 335 primary liver transplants performed in children at the University of Pittsburgh Medical Center was examined. No difference in transplant outcome was demonstrated in children based on the gender pairings between the donor and recipient whether or not variables such as the age, etiology of the liver disease, and the blood group of the recipient were included in the data analysis. Thus, in contrast, to the situation in adults, the gender of the donor does not influence the outcome of liver transplantation in children and should not be used as a criterion for donor selection. This difference between adults and children may be due, at least in part, to gender differences in hepatocyte phenotypic expression induced as a consequence of puberty.

Relation of obesity, high sodium intake, and eccentric left ventricular hypertrophy to left ventricular exercise dysfunction in essential hypertension

PURPOSE

To elucidate determinants of abnormal left ventricular functional responses to exercise in hypertensive patients.

PATIENTS AND METHODS

One hundred twenty-seven patients with uncomplicated essential hypertension were studied by rest and exercise radionuclide angiography and by echocardiography at rest.

RESULTS

The 24 patients with subnormal left ventricular ejection fraction at peak exercise (less than 54%) were similar in age and rest and exercise blood pressures to the 103 with normal exercise ejection fraction, but were more obese (p less than 0.005) and had greater left ventricular mass (p less than 0.03) and internal dimensions (p less than 0.001). The parallel increase in left ventricular chamber size and mass (eccentric hypertrophy) in the group of patients with exercise dysfunction was associated with higher resting end-systolic wall stress (p less than 0.001) and abnormal increases of end-systolic left ventricular volume from rest to peak exercise (p less than 0.001). Multivariate analysis revealed that exercise left ventricular dysfunction was independently associated with higher left ventricular mass (p less than 0.0005), end-systolic wall stress (p less than 0.001), dietary sodium intake (p less than 0.01), and body mass index (p less than 0.03).

CONCLUSION

Among patients with uncomplicated essential hypertension, abnormal functional responses to exercise are strongly associated with eccentric ventricular hypertrophy, obesity, and high sodium intake.

Transtubular potassium concentration gradient: a useful test to estimate renal aldosterone bio-activity in infants and children

The present investigation was designed to validate the usefulness of transtubular potassium (K) concentration gradient (TTKG) as an indicator of aldosterone bio-activity in infants and children. TTKG was calculated by the formula: [K]urine: (urine/plasma)osmolality/[K]venous blood. We compared this index with fractional K excretion (FEK) and urine K concentration to urine sodium (Na) concentration ratio (UK/UNa) in 473 normal children aged 1 month-15 years. Values of TTKG followed a non-gaussian distribution (median, 6.3; 3rd centile, 4.1; 97th centile, 13.4). TTKG in infants (n = 108; median, 7.8) was significantly higher than in children (n = 365; median, 6.0). TTKG correlated directly with FEK and UK/UNa. Indices of K excretion were also assessed in 13 patients with hypo- and pseudohypoaldosteronism. TTKG values varied between 1.6 and 4.1 and were all below the 3rd percentile established for the age of the subject. We conclude that calculation of TTKG is an easy and sensitive method for the evaluation of mineralocorticoid action in distal and collecting tubules.

Diethylstilbestrol potentiates and testosterone antagonizes the action of 3-methylcholanthrene on benzo(a)pyrene metabolism in Hep G2 cells

We have used the human hepatoma cell line, Hep G2, to examine the ability of hormones and xenobiotics to modulate the hepatic induction of benzo(a)pyrene hydroxylase and epoxide hydrolase. Hep G2 cells were cultured in Eagle's Minimum Essential Medium supplemented with 10% fetal calf serum. 3-Methylcholanthrene, diethylstilbestrol, testosterone propionate, and combinations of 3-methylcholanthrene, and each of the hormones were added directly to the culture media. We subsequently studied the metabolism of benzo(a)pyrene using cell lysates of the Hep G2 cells. Metabolites were quantitated by high-performance liquid chromatography (HPLC) using fluorodetection. Exposure to 3-methylcholanthrene alone resulted in an eightfold increase in total benzo(a)pyrene metabolites with a change of the predominant metabolite from the 3-hydroxybenzo(a)pyrene to the carcinogenic pathway of the benzo(a)pyrene-7,8-diol. Diethylstilbestrol and testosterone propionate resulted in small, but significant, decreases in metabolism of benzo(a)pyrene. When exposed in combination with 3-methylcholanthrene, testosterone propionate antagonized and diethylstilbestrol potentiated the metabolism of benzo(a)pyrene. 3-Methylcholanthrene, diethylstilbestrol, and combinations of 3-methylcholanthrene and diethylstilbestrol or testosterone propionate resulted in increased epoxide hydrolase activity as compared to controls. These results, carried out in a human hepatoma cell line, lend support to a concern for potentiated toxicity and carcinogenicity following exposure to complex chemical mixtures.

Comparison of the vascular and glomerular changes in aortic-ligature and DOCA-salt hypertension

1. Animals and histology from two previous investigations were used to test the hypothesis that a similar elevation in blood pressure may result in a different sequence of pathological changes in different experimental models of hypertension, DOCA-salt and aortic-ligature hypertension. 2. To asses differences in morphological parameters, individual animals in the two groups were paired (n = 12) for the same level of blood pressure at sacrifice. 3. Vascular damage was significantly less in the DOCA-salt group (P less than 0.01). Glomerular lesions however were more severe in the DOCA-salt group. In rats with aortic-ligature hypertension significantly fewer glomeruli had fibrinoid and/or crescents than in DOCA-salt rats (P less than 0.001). There were fewer glomeruli with epithelial cell droplets (ECD) and fewer ECD per glomerulus in aortic-ligature when compared with DOCA-salt hypertension (P less than 0.001, P less than 0.001, respectively). 4. This study highlights the significance of factors other than blood pressure per se in producing vessel and glomerular lesions in experimental hypertension.

Estradiol and testosterone levels in patients undergoing partial hepatectomy. A possible signal for hepatic regeneration?

In five adult male patients undergoing a 40-60% partial hepatectomy, serum sex hormone levels before and after hepatic resection were determined. Blood was drawn immediately prior to each surgical procedure and at specified time points postoperatively. Compared to hormone levels found prior to surgery, following major hepatic resection, estradiol levels increase at 24 and 48 hr, while testosterone levels decline, being significantly reduced at 96 and 144 hr. These data demonstrate that adult males who undergo a 40-60% partial hepatectomy experience alterations in their sex hormone levels similar to those observed in male rats following a 70% hepatectomy. These changes in sex hormone levels have been associated in animals with an alteration of the sex hormone receptor status of the liver that is thought to participate in the initiation of the regenerative response. These studies suggest, but do not prove, that in man, as in the case of the rat, sex hormones may participate in the initiation of or at least modulate in part the regenerative response that occurs following a major hepatic resection.

Characterization of estrogen receptor from human liver

Characterization of the estrogen receptor in cytosol from human male liver was undertaken to further understanding of the molecular basis of estrogen action in this tissue. By analysis of estrogen binding data of crude cytosol, saturable estrogen binding showed a Kd = 4.7 X 10(-10) M. High levels of nonsaturable binding were also detected. The estrogen-binding activities detected could be distinguished by their steroid specificity, hydrodynamic parameters, ionic properties, and sensitivity to proteolytic attack. Our findings also confirmed that the moderate-affinity estrogen binders found in rodent liver cannot be detected in human tissue. We concluded that the properties of estrogen receptor of human liver cytosol allow its separation from nonsaturable estrogen-binding components.

Has plasma renin activity a prognostic significance in subarachnoid haemorrhage?

The possible relationship between plasma renin activity and neurological deficits was examined in ten patients with spontaneous subarachnoid haemorrhage in a prospective clinical study. The patients were examined daily, particular attention being given to signs of brain stem dysfunction. The degree of impaired consciousness was assessed using the Glasgow Coma Score. Plasma renin activity was determined on days 1-5, 7, 9, 11, 13, 15 and 21 after the initial bleeding episode using an Angiotensin-I-radioimmunoassay. Six of seven patients with signs of brain stem dysfunction displayed a marked increase in plasma renin activity. Thus a significant negative correlation between the degree of consciousness and the plasma renin activity resulted. An explanation for this correlation may be found in the localization of the autonomous centres and the high concentrations of renin in the hypothalamus and brain stem. The individual changes in plasma renin activity have prognostic significance, whereas single estimated plasma renin activities show great inter-individual differences and have only limited prognostic value.

Inhibition of angiotensin converting enzyme by (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo-2,3,4,5-tetra- hydro-1,5-benzothiazepine-6-acetic acid (CV-5975), a non-sulfhydryl compound

CV-5975, (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo- 2,3,4,5-tetrahydro-1,5-benzothiazepine-5-acetic acid, was found to inhibit rabbit lung angiotensin converting enzyme (ACE) activity with an IC50 of 3.1 x 10(-9) M and a Ki of 2.6 x 10(-9) M, inhibit the angiotensin I (A-I)-induced contraction of the guinea pig ileum with an IC50 of 1.3 x 10(-8) M, and augment the bradykinin (BK)-induced contraction of the ileum with an AC50 of 9.2 x 10(-10) M. The activity of CV-5975 was comparable to or slightly more potent than that of enalaprilat. The overall inhibition constant (Ki*), calculated from a steady-state analysis of enzyme reactions, was 4.4 x 10(-12) M for CV-5975; this indicates that the inhibition was about 5 times more potent than that of enalaprilat (2.0 x 10(-11) M). In rats, CV-5975 (0.03 and 0.3 mg/kg, i.v. and 3 and 10 mg/kg, p.o.) inhibited the A-I-induced pressor action more potently and for a longer period than did the corresponding doses of enalaprilat and enalapril. CV-5975 and enalapril (3 mg/kg, p.o.) augmented the BK-induced depressor action to a similar extent. In dogs, CV-5975 (0.3 and 1 mg/kg, p.o.) markedly inhibited the A-I-induced pressor action in a dose related manner, and the duration of this inhibitory activity was longer than with the corresponding doses of enalapril. These data provide evidence for the proposal that CV-5975 is a highly potent and long lasting ACE inhibitor.

Efficacy and safety of lisinopril in older patients with essential hypertension

Angiotensin-converting enzyme inhibitor therapy has been thought to be more effective in hypertensive patients with normal or elevated levels of renin in the plasma. However, several studies have challenged this concept by demonstrating the efficacy of angiotensin-converting enzyme inhibitors (captopril and enalapril) in older patients, among whom a low level of renin activity in the plasma is common, and in other patients with low-renin essential hypertension. Lisinopril, a new long-acting angiotensin-converting enzyme inhibitor, also has been shown to be an effective antihypertensive agent in older patients. This report examines data from 97 older and 710 younger hypertensive patients enrolled in four multicenter trials of eight to 12 weeks' duration. In these trials, the dose of lisinopril was titrated until a diastolic pressure of less than 90 mm Hg was reached, or to a maximal dose of 80 mg per day. In general, the antihypertensive effect achieved in older patients with lisinopril was equal to or greater than that achieved in younger patients. The drug was generally well tolerated. Lisinopril can be expected to be used frequently in older patients.

Relation of concentric left ventricular hypertrophy and extracardiac target organ damage to supranormal left ventricular performance in established essential hypertension

Increased cardiac performance has been documented in patients with early systemic hypertension, but its prevalence and determinants in patients with uncomplicated sustained essential hypertension have not been characterized. Radionuclide cineangiography in 116 patients with uncomplicated essential hypertension showed that 12 of 116 (10%) had supranormal resting left ventricular (LV) ejection fraction (greater than 70%, above the highest value in normal subjects), while 104 patients had a normal resting ejection fraction (45 to 70%). Patients with a high resting ejection fraction had higher systolic and diastolic blood pressure compared with patients with normal resting ejection fraction (182 mm Hg vs 169, p less than 0.01, and 110 vs 103, p less than 0.05, respectively), markedly greater echocardiographic LV mass (136 vs 94 g/m2, p less than 0.01), smaller ventricular dimensions in systole (2.5 vs 3.1, p less than 0.01) and diastole (4.4 vs 4.9, p less than 0.05), and higher relative wall thickness (0.61 +/- 0.20 vs 0.39 +/- 0.98, p less than 0.001). Patients with supranormal resting ventricular performance had lower end-systolic wall stress than normal volunteers or patients with normal resting LV function (48 vs 64 vs 74 X 10(3) dynes/cm2, respectively). Patients with an elevated LV ejection fraction also had significantly more abnormal funduscopic examinations and greater proteinuria. Thus, a subset of essential hypertensive patients with moderately to severely elevated blood pressure developed marked concentric LV hypertrophy associated with subnormal end-systolic stress and supranormal LV performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac arrhythmias in subarachnoid haemorrhage

In this prospective study 52 patients with spontaneous subarachnoid haemorrhage were examined with respect to cardiac arrhythmias and their relationship to cerebral lesions. A continuous ECG was registered over an average of five days. Sinus tachycardia was the most frequently recorded arrhythmia, followed by multifocal ventricular extrasystoles, couplets, frequent supraventricular extrasystoles, non-sustained ventricular tachycardia, asystolia and sinus arrhythmia. A significant correlation was found between the clinical manifestation of a midbrain syndrome and sinus arrhythmia, and multifocal ventricular extrasystoles. This correlation points to the autonomic cardiovascular centres as the structures involved.

Two forms of vasoconstriction in systemic hypertension

Clinical, pharmacologic and biochemical evidence characterizes essential hypertension as a heterogeneous spectrum of pathophysiologic substances rather than the single entity it has long been presumed to be. Although the causes of essential hypertension remain obscure, 2 different mechanisms for long-term vasoconstriction that sustain diastolic hypertension in the experimental and clinical forms of primary aldosteronism and renovascular hypertension can also be identified and quantified among patients with essential hypertension. The first mechanism is renin independent, requires antecedent sodium retention and appears related to abnormal membrane transport of calcium. This vasoconstriction is identified by low plasma renin and ionized calcium and is correctable by sodium depletion or calcium channel or alpha blockade. The second vasoconstrictor mechanism is renin mediated and involves an increase in cytosolic calcium. This mechanism is quantifiable by the plasma renin level or the hypotensive response to an antirenin-system drug (converting enzyme inhibitor, beta blocker or saralasin). Depending on the state of sodium balance, these 2 mechanisms contribute reciprocally to maintenance of arteriolar tone in experimental models, in both normal and hypertensive people, and in patients with congestive heart failure. In these situations, at the extremes of the range of plasma renin values, one or the other mechanism predominates, whereas in the medium range of renin values both mechanisms can be operative. These interrelations provide a basis for applying more precisely tailored therapy and for stratifying patients pathophysiologically for further study.

Hepatic estrogen receptor in human liver disease

Human liver contains estrogen receptors which render it sensitive to estrogen. Specific hormone binding to cytosol and nuclei from normal liver containing such receptors is of high affinity, low capacity, saturable, and specific for steroidal and nonsteroidal estrogens. Although estrogens alter metabolism and may produce disease, little data is available concerning estrogen receptor levels found in diseased liver. Herein we report estrogen receptor levels in human female liver containing diseases associated with oral contraceptives. Binding studies demonstrated cytosolic and nuclear estrogen receptors in human hepatic adenoma and focal nodular hyperplasia. Nuclear estrogen receptor levels in neoplastic tissue were greater than those in normal tissue. In addition, one hepatic adenoma resected from a patient taking tamoxifen contained no cytosolic estrogen receptor, and nuclear estrogen receptor levels were significantly lower than those found in normal tissue. These differences in binding capacity suggest a potential for greater hormone responsiveness in neoplastic liver tissue.

Endothelium-dependent vascular responses in normotensive and hypertensive Dahl rats

Experiments were designed to study endothelium-dependent responses in salt-sensitive (DS) and salt-resistant Dahl rats (DR). The rats were fed a low sodium (0.1% NaCl) or high sodium (8% NaCl) diet for 8 weeks. Blood pressure in DS fed a high sodium diet was higher than that in the remaining animals. Aortic rings with and without endothelium were suspended for isometric tension recording. Acetylcholine, adenosine 5'-diphosphate, and thrombin induced endothelium-dependent relaxations that were significantly depressed in the aorta of DS fed a high sodium diet. The relaxations in response to sodium nitroprusside were only slightly, but significantly, depressed in DS fed a high sodium diet. Removal of the endothelium greatly enhanced the response to serotonin and norepinephrine. In rings with, but not without, endothelium taken from rats fed a high sodium diet, the tension developed in response to serotonin and norepinephrine was significantly greater than that in animals fed a low sodium diet. These experiments indicate that endothelium-dependent relaxations to acetylcholine, adenosine 5'-diphosphate, and thrombin are depressed in hypertensive Dahl rats; this effect probably reflects a decreased release of endothelium-derived relaxing factor(s), although structural changes might contribute; and the responsiveness to vasoconstrictor agents is increased in DS and DR fed a high sodium diet. These findings may indicate differential effects of blood pressure and dietary salt on endothelial function.

Estrogen receptors and androgen receptors in the mammalian liver

An estrogen receptor and an androgen receptor are present in the mammalian liver. In the liver of the rat, the estrogen receptor concentration increases markedly at puberty and this change correlates with enhanced estrogen stimulation of plasma renin substrate synthesis. High doses of estrogen are required for nuclear binding in liver when compared to doses for the uterus. The high dose requirement appears to be predominantly due to extensive metabolism in the hepatocyte of the estrogen to inactive derivatives. Furthermore, estradiol is much weaker than ethinyl estradiol for promoting nuclear binding in the liver. This is due to extremely rapid and extensive metabolism of estradiol. In human liver the concentration of estrogen receptor is low. An androgen receptor is present in high concentration in rabbit liver and is located predominantly in the nucleus after androgen administration. High concentrations of a putative androgen receptor are also present in human liver cytosol. Preliminary studies indicate that synthetic progestins can attach to the human liver androgen receptor. To date, a progesterone receptor has not been found in the mammalian liver. Thus, it appears that extensive steroid metabolism in liver preferentially diminishes sex steroid interaction with liver receptors and that androgen receptors may mediate progestin effects in liver. These observations provide a scientific basis for improved safety of oral contraceptives. Lowering the estrogen and progestin doses in oral contraceptives will decrease the major side-effects, which are liver mediated, and still maintain the desired effects at the hypothalamic-pituitary axis and uterus. Furthermore, it is likely that by selecting which estrogen, progestin or androgen is administered as well as by utilizing a parenteral route of administration that sex steroid effects on the liver could be minimized.

The role of the sympathetic nervous system in oestrogen-induced hypertension in rats

Albino rats of either sex received chronic ethinyl oestradiol (EO) treatment (1.5 mg kg-1 daily, i.m.) for 3 weeks. Untreated control rats received arachis oil vehicle alone. Chronic EO treatment resulted in elevation of blood pressure in both sexes. Female rats exhibited significantly greater elevation in blood pressure than males. In chronic EO-treated rats pressor responses to low doses (0.5 micrograms kg-1) of noradrenaline were significantly increased, while those to angiotensin II, acetylcholine and isoprenaline were unaltered. Chronic EO treatment also sensitized the vascular bed of the rats' hindquarters to noradrenaline. EO-induced hypertension was associated with significant increase in dopamine-beta-hydroxylase activity of adrenal glands. Complete bilateral adrenalectomy or chemical sympathectomy prevented the development of EO-induced hypertension. It is suggested that chronic treatment of rats with EO induces and maintains hypertension. The peripheral sympathetic system plays an important role in this phenomenon.

Cardiac structure and function in renovascular hypertension produced by unilateral and bilateral renal artery stenosis

To evaluate cardiovascular status in human renovascular hypertension, quantitative echocardiographic findings were compared in 42 patients with arteriographically documented renovascular hypertension and 46 age- and sex-matched patients with essential hypertension. Left ventricular (LV) fractional shortening, a measure of systolic performance at rest, was subnormal (less than 26%) in 8 of 42 renovascular hypertensive patients (19%), 0 of 42 essential hypertensive patients (p less than 0.005) and 1 of 79 normal subjects (1%) (p less than 0.005). Fractional shortening was equally reduced in patients with arteriosclerotic and nonarteriosclerotic causes of renal artery stenosis (32 +/- 9% vs 32 +/- 6%, both p less than 0.025 compared with 36 +/- 5% in patients with essential hypertension). The depressed function in renovascular hypertension appeared to be a result of greater LV dilation (p less than 0.02) and septal but not LV free wall hypertrophy (p less than 0.01) that failed to offset the pressure load, allowing end-systolic stress, a measure of myocardial afterload, to increase to abnormal levels (101 +/- 47 X 10(3) dynes/cm2, p less than 0.001 vs 68 +/- 19 in essential hypertension). These data indicate that human renovascular hypertension is associated with more adverse cardiac involvement than essential hypertension of similar severity. In addition, the 14 patients with bilateral renovascular stenosis had a higher cardiac index (3.9 +/- 1.1 liters/min/m2) than the 28 with unilateral stenosis (3.2 +/- 1.1 liters/min/m2, p less than 0.05). This result supports the proposition that bilateral renovascular disease is analogous to 1-clip 1-kidney experimental renovascular hypertension, while unilateral renovascular disease resembles the 1-clip 2-kidney model.(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian rhythm of hepatic cytosolic and nuclear estrogen and androgen receptors

Mammalian liver is a sex steroid-responsive tissue. The effects of these hormones presumably are mediated by hepatic estrogen receptors (ER) and androgen receptors (AR). Serum levels of sex hormones display circadian rhythms. Further, estrogens and androgens are commonly administered; administration of these agents is associated frequently with liver disease. Therefore, we investigated whether the cytosolic and nuclear sex steroid receptors also display a similar circadian rhythm, and whether variations occurred in the distribution of receptors between cytosolic and nuclear compartments. Animals were killed every 4 h from midnight till the following midnight; cytosolic and nuclear levels of both ER and AR were measured. Cytosolic ER reached a maximum level at 4 AM, and a minimum at 8 PM and midnight of both days. Nuclear ER was highest at 8 AM and lowest at 4 PM and 8 PM, a pattern which parallels variations in serum estradiol levels. Cytosolic AR was highest at 8 PM and lowest at midnight and 4 AM. Nuclear AR was highest at 4 AM and lowest at 4 PM and 8 PM. The highest level of nuclear AR does not correspond to the maximum serum testosterone level, which occurred at 4 PM. The total hepatic content of both ER and AR was not constant over the 24-h period, but varied considerably with time of day. These studies suggest that both ER and AR show a distinct circadian rhythm in subcellular compartmentalization, and that total hepatic content of ER and AR varies significantly during a 24-h period.

Effects of two forms of hypertension on atherosclerosis in the hyperlipidemic baboon

We examined the relationship of hypertension and plasma renin activity to atherogenesis in 48 moderately hyperlipidemic (total serum cholesterol was about 200 mg/dl) baboons (Papio sp.). We used renal artery stenosis (two-kidney, one clip model) to produce hypertension associated with elevated plasma renin activity, and used cellophane wrapping of both kidneys (bilateral perinephritis model) to produce hypertension with normal renin activity. Renal artery stenosis and bilateral perinephritis increased both systolic and diastolic blood pressure by about 30 mm Hg. Renal artery stenosis approximately doubled, but bilateral perinephritis did not change plasma renin activity. Both hypertensive groups, to about the same degree, had significantly more extensive atherosclerosis than the control group in the abdominal aorta and brachial, iliac-femoral, and carotid arteries. The effect of hypertension was greatest in the carotid arteries where the extent of atherosclerosis was nearly tripled. Hypertension did not influence lesions in the thoracic aorta. By multiple regression analysis, very low plus low density lipoprotein cholesterol, high density lipoprotein cholesterol, and systolic blood pressure were consistently strong predictive variables for the extent of atherosclerotic lesions. Most of the effects of renal hypertension on atherosclerotic lesions appeared to be accounted for by the increase in blood pressure. In the carotid arteries, however, there was a suggestion of an effect above that due to increased blood pressure. Additional analyses indicated that these treatment effects were associated with serum potassium concentration, plasma renin activity, or other closely related variables.

Endogenous angiotensin-aldosterone-pressure relationships during sodium restriction

The effects of moderate restriction of dietary sodium and potassium supplementation on plasma levels of renin, angiotensin II, aldosterone, and cortisol and on arterial pressure were studied in 12 patients with mild essential hypertension. To define hormone-blood pressure relationships, venous hormone levels were measured hourly and intra-arterial pressure continuously for 24 hours after 4 to 6 weeks of sodium restriction, 4 to 6 weeks of potassium supplementation, and a similar period of control diet. Our results show that compared with the control diet, moderate sodium restriction was associated with increased levels of aldosterone but no overall change in renin, angiotensin II, or cortisol levels. Further, slopes of regression lines relating log renin and log angiotensin II to aldosterone were increased, as were log cortisol/aldosterone regression lines. On the contrary, regression lines of log renin and log angiotensin II versus arterial pressure were unaltered by sodium restriction. Hormone and blood pressure relationships were not changed by the potassium supplemented diet. Although confirmatory data are needed, our findings suggest that moderate sodium restriction enhances aldosterone responsiveness to endogenous angiotensin II and adrenocorticotropic hormone without diminishing the pressor activity of endogenous angiotensin II. These results may explain in part the disappointingly small hypotensive effect of modest sodium restriction in mild essential hypertension.

Essential hypertension: a metabolic cause? A hypothesis

Forty-five hypertensive patients, 28 women and 17 men, age range between 35 and 65 years (mean 50 years), with blood pressures which current therapy did not succeed to control, were submitted to several examinations in order to identify the cause of their hypertension. We found isolated or combined abnormal values of aldosterone, renin, calcium and or potassium as the only alterations in 19 patients. We distinguished 4 groups descretionally classified according to biochemical alterations: renin and aldosterone increase, renin increase, aldosterone increase, calcium and or potassium reduction. The therapy used, intentionally aimed at the correction of the biochemical alterations found. Normal blood pressure was achieved in all patients and simultaneously the biochemical alterations also became normal in patients with isolated hyperreninemia, with combined hyperreninemia and hyperaldosteronemia and in those with hypocalcemia and or hypopotassemia. In patients were only isolated hyperaldosteronemia was found, this condition returned to normal in all except one. We suggest that besides the disturbances in sodium distribution other electrolytes or biochemical alterations may also play an equally important role in regulating, and sustaining essential hypertension.

Surgical management of primary aldosteronism (Conn's syndrome), a correctable cause of hypertension

Clinical, operative and pathological findings in a series of 18 patients with aldosterone producing adrenal cortical adenomas are reviewed. All patients presented with hypertension and hypokalaemia. The main challenges in preoperative diagnosis were to differentiate primary aldosteronism from other causes of hypokalaemia, such as diuretic therapy, to establish the presence of a discrete adenoma and to localize the tumour to the left or right adrenal gland. A high rate of success was achieved in predicting a surgical diagnosis of aldosterone-producing adenoma. This was attributed to thorough biochemical evaluation of the underlying metabolic state by measurement of renal potassium handling and by determining the responses of the renin-aldosterone axis to changes in sodium balance. Preoperative tumour localization, using adrenal phlebography or scintiscanning, was accomplished in only eight cases. Our experience suggests that the transabdominal approach is preferable for cases in which a unilateral lesion is not clearly identified by imaging techniques.

Whole blood viscosity as a determinant of cardiac hypertrophy in systemic hypertension

The relationships among blood pressure (BP), blood viscosity and echocardiographic left ventricular (LV) muscle mass were evaluated in 24 patients with essential hypertension and in 13 normotensive control subjects. LV mass was greater in the hypertensive patients than in the control subjects (225 +/- 69 vs 170 +/- 31 g, p less than 0.02) as was blood viscosity at a shear rate of 104 sec-1 (4.7 +/- 0.1 vs 4.3 +/- 0.2 cp, p less than 0.005). Among the hypertensive patients, LV mass was most closely related to viscosity at 104 sec-1 (r = 0.80, p less than 0.001), whereas only weak correlations were found between LV mass and systolic or diastolic BP (r = 0.45, p less than 0.05 for both). The 14 hypertensive patients with normal LV mass had viscosity similar to that in control subjects (4.5 +/- 0.3 vs 4.3 +/- 0.2 cp), whereas viscosity was consistently increased (5.0 +/- 0.4 cp, p less than 0.02) in hypertensive patients with LV hypertrophy. Thus, increased blood viscosity may be a determinant of or a response to hypertensive cardiac hypertrophy.

Modification of stepped care approach to antihypertensive therapy

"Stepped care" is a standardized recipe for uniform treatment of hypertension that has produced useful information on the effectiveness of long-term antihypertensive therapy. However, experience with this unimodal approach to treatment has also revealed its weaknesses. Conceptually, stepped care ignores the possible importance of the means by which blood pressure is reduced and leads to drug overuse since there is no systematic plan for drug subtraction or dose reduction. Moreover, stepped care has never been critically tested against other algorithms. From a practical standpoint, stepped care has never been shown to protect from coronary events, the major burden of hypertension; in several studies, these events may have been increased, probably by the inclusion of a diuretic in the regimen. Such results indicate that a single recipe for all, based on a single process hypothesis, may be hazardous. A critical current issue is the question of whether it matters how the blood pressure is reduced. Thus, diuretics reduce pressure by lowering volume and flow whereas the modern agents, converting enzyme inhibitors and calcium influx inhibitors, reduce pressure while actually improving flow to the target organs. With the availability of more potent and palatable agents with different specificities, and with the increasing awareness of the heterogeneity of essential hypertension and the means to demonstrate it (that is, renin profiling), treatment strategies should be designed and tested in which single drug types are selected for their specificity and their long-term benefits evaluated. In a proposed model, beta blockers or converting enzyme inhibitors are given first to patients with medium or high renin levels and calcium blockers or diuretics to patients with low renin levels. The likely possibility that preservation of flow is a more relevant goal than reduction of pressure per se requires critical examination.

Renovascular hypertension associated with bilateral aldosteronoma

The authors present a 35-year-old male patient with renovascular hypertension caused by the stenosis of both renal arteries of the right kidney. Two years after the diagnosis of hypertension was made, an endarterectomy was performed but a successful correction of the upper stenotic artery was not achieved. During the next 2 years the hypertensive disease was uncontrollable with antihypertensive medications and gradually entered into a malignant phase. In addition to the atrophy of the right kidney, an adenoma of the left adrenal gland was revealed (19.75 g) which was operated on. Left adrenalectomy had only a transitory benefit on blood pressure level. Five months later an adenoma of the right adrenal gland was diagnosed and together with the ischaemic right kidney was operated on (right adrenalectomy and nephrectomy) which definitely cured the hypertension. The chronological sequence of events and the course of the disease in the patient point to the possibility that long-standing hyper-reninaemia, due to renal ischaemia, may cause the development of multiple bilateral adrenocortical adenomas and that secondary aldosteronism may transform into primary.

Blood pressure and plasma renin activity responses to chronic stress in the borderline hypertensive rat

The purpose of this study was to examine the systolic blood pressure and plasma renin activity (PRA) responses to chronic stress in normotensive rats and in rats with one hypertensive parent. Twenty-four male Wistar-Kyoto (WKY) and 24 male F1 offspring of spontaneously hypertensive and WKY rats (BHR) were randomly assigned to 3 groups of 8 each. Experimental (E) animals were subjected to 2 hr daily of shock-shock conflict. Each response produced a 0.2 sec, 0.2-0.4 mA cutaneous electric shock. Failure to respond in 10 sec resulted in a train of 5 shocks (0.2 sec each sec). Yoked animals (Y) received the same shocks as E but had no control over their presentation. Finally, a control group (C) for maturation received no shocks. The E and Y animals were subjected to 14 weeks of conflict and were then monitored an additional 14 weeks in the absence of shock. All animals had their tail cuff blood pressures taken weekly except for 3 times when bloods were obtained for PRA assays. Analysis of blood pressure data revealed that:(1) BHR animals showed more of a blood pressure response to shock than WKY animals; (2) Y animals showed more of a response to conflict than E, especially for the BHR group; and (3) BHR shocked animals remained permanently elevated compared to BHR control animals even in the 14 week post-conflict period during which no shocks were given. Although PRAs for BHR animals were significantly higher than for WKY at the beginning of study, the stress-induced hypertension was associated with either normal or suppressed PRA values, suggesting that the hypertension in these animals is not a high renin hypertension.

Renin system activity as a determinant of response to treatment in hypertension and heart failure

In hypertension, irrespective of its underlying etiology, the baseline pretreatment renin-sodium profile predicts the antihypertensive action or the lack of it for five major types of antihypertensive drugs: 1) diuretic agents; 2) beta-receptor blockers; 3) converting-enzyme inhibitors; 4) the alpha 1 postsynaptic blocker, prazosin; and 5) the calcium channel blockers, verapamil and nifedipine. Moreover, vigorous compensatory activation of the renin-angiotensin system in response to therapy often explains initial drug ineffectiveness or resistance to treatment by diuretics and nonspecific vasodilators. This correlation between renin system behavior and antihypertensive drug efficacy likely reflect basic pharmacologic-physiologic interactions. This correlation is also observed in congestive heart failure without hypertension, where operant renin-aldosterone profiles may help to explain both drug efficacy and drug resistance to commonly administered therapeutic agents. Accordingly, a control system analysis of the renin axis has broad applications in therapy. The analysis is also conceptually significant since it exposes the operation of fundamentally different mechanisms of increased vascular resistance to flow occurring in different patients with hypertension or heart failure. One form is renin-angiotensin-mediated whereas the other, in the absence of renin, is associated with sodium-volume excess and/or abnormal alpha-adrenergic and calcium channel activity. Further definition of these two mechanisms of increased peripheral resistance could lead to a better understanding of the pathogenesis of some forms of essential hypertension and congestive heart failure.

Comparison of propranolol or hydrochlorothiazide alone for treatment of hypertension. III. Evaluation of the renin-angiotensin system

In this study, the relation between renin activity and therapeutic response to hydrochlorothiazide or propranolol was studied. Patients with a diastolic blood pressure of 95 to 114 mm Hg were treated with propranolol (40 to 320 mg twice daily) or hydrochlorothiazide (25 to 100 mg twice daily). The initial renin profiles were: low, 56 percent (n = 300); normal, 33 percent (n = 174); high, 11 percent (n = 60). A greater incidence of low and fewer high renin profiles (p less than 0.001) were observed in blacks. After furosemide administration (40 mg intravenously), 55 percent of patients (n = 291) had a low renin response and 45 percent (n = 240) had a normal renin response. No correlation between renin profile and renin response was observed, although low renin response and low renin profile occurred more frequently in older patients. Hydrochlorothiazide administration resulted in a greater decrement in diastolic blood pressure (p less than 0.05) in the total group. Irrespective of renin activity, both hydrochlorothiazide and propranolol reduced diastolic blood pressure. When renin profile was considered, no significant variation in response to hydrochlorothiazide therapy was observed, and there was a greater reduction in diastolic blood pressure in the patients with a high renin profile receiving propranolol. In comparing therapeutic response, patients with a low renin profile had a better response to hydrochlorothiazide, and propranolol was more effective in patients with a high renin profile. The anticipated effect of therapy on plasma renin activity was observed. Although these results are consistent with a volume-vasoconstrictor analysis of hypertension, the results of therapy could not have been prejudged from renin profile or responsivity. The slight differences observed do not warrant the expense of renin determinations when a simple determination of therapeutic response is sufficient.

The renin system for long-term control over vasoconstriction and sodium-volume homeostasis in the spectrum of hypertension: three new frontiers in research

This morning I have presented something old and something new and I have tried to point out what I think are some promising areas of current research. In the past two decades we have made great strides in our understanding of hypertensive mechanisms. We now know that essential hypertension can no longer be viewed an a single entity. Its heterogeneity in renin patterns is matched by heterogeneity in response or lack of response of individual patients to different types of drugs, and by heterogeneity in risk and prognosis. Analysis of renin system patterns has proven to be very productive for enabling us to understand the participation of the vasoconstriction or volume factors that inevitability work to maintain all hypertensive states. This bipolar analysis of hypertensive phenomena in turn has led to better diagnosis and to more specific treatment of individual patients. In our present state of knowledge, we still need to understand why the renin system so often inappropriately participates in maintenance or causation of the hypertensive state and why it fails to turn itself off in medium or high renin patients. In the low renin patients we do not understand why renal sodium retention occurs nor how it produces sustained increases in peripheral resistance. Three of many potentially exciting areas for expanding our knowledge are the prorenin problem, the natriuretic hormone problem, and the recently discovered relationships between the divalent cations, calcium and magnesium, and the concurrent renin system patterns in the renin subgroups of essential hypertension. Perhaps one of these areas will serve as an appetizer for the participants here today, and in particular for the man we honor, Franz Gross.

Achievements in hypertension: a 25 year overview

Only 25 years ago, the field of hypertension was challenged by retrospective clinical data and epidemiologic information suggesting that an elevated arterial pressure is a major risk factor for enhanced cardiovascular morbidity and mortality. Not only was antihypertensive therapy looked on by many as dangerous and fraught with severe and undesirable side effects, but its validity in reversing the course of disease was not yet demonstrated. This review discusses the dramatic new information amassed over the past 25 years that points to the new physiologic and clinical concepts concerning hypertension. It considers impressive new diagnostic techniques and methods designed to identify secondary forms of hypertension and target organ involvement. In summary, it outlines the feasibility of reversing overall (and cardiovascular) morbidity and mortality with an array of antihypertensive agents that provide the therapeutic ability to suppress most pathophysiologic pressor mechanisms of hypertensive disease. The lesson is clear: hypertension provides the greatest available challenge to the new era of preventive cardiology in the 21st century.

Renin, renin inhibition and antihypertensive therapy

Research over the last 25 years established the renin-angiotensin-aldosterone system's important role in electrolyte and blood pressure homeostasis as well as in the pathophysiology of hypertension for which renin suppressive drugs, angiotensin antagonists and converting enzyme inhibitors provided selective pharmacological tools. Pharmacological interference with the renin-angiotensin axis in addition to reducing angiotensin-mediated vasoconstriction reduces angiotensin's effect on aldosterone, alpha-adrenoceptor mediated vasoconstriction and central activation of sympathetic nerve activity. Renin measurements serve as an endocrine marker for the activity and reactivity of the sympathetic nervous system reflecting a beta-adrenoceptor mediated response which tends to decrease with older age. Therefore, as younger the patient and as higher pretreatment renin as better the antihypertensive response to converting enzyme inhibitors and betablockers is. As lower renin and as older the age diuretic agents and calcium antagonists are more effective, the hyporesponsive renin being a co-determinant of pressure response in these patients.

The effect of angiotensin II on in vivo albumin transport in normal rabbit aortic tissue

Angiotensin II and other vasoactive amines may have a direct effect on the permeability of the arterial wall. We have investigated the effect of angiotensin II in vivo albumin transport across the aortic wall in rabbits following intravenous injection of [125I]albumin. Transmural concentration profiles of 125I-labeled albumin across the intima and media of the aorta, generated during 25 min of either angiotensin or saline infusion, were measured by a serial-sectioning technique. The uptake of labeled albumin through the aortic wall was found to be dependent on position and to increase from the descending thoracic up to the arch. Angiotensin infusion increased albumin uptake in the region of the aorta proximal to the first pair of intercostal arteries and magnified the position dependence. Angiotensin infusion did not change the uptake of albumin in the descending thoracic aorta between intercostal arteries. The arterial blood pressure elevation associated with angiotensin infusion was not of prime importance in producing the uptake patterns described above.

Left ventricular hypertrophy and function in high, normal, and low-renin forms of essential hypertension

To assess the relative importance of the level of blood pressure (BP) and renin profile status as determinants of hypertensive left ventricular hypertrophy (LVH) and dysfunction, we studied, by quantitative echocardiography, 118 hypertensive patients off medication. The 19 high-renin patients were younger (31 +/- 13 years; p less than 0.01) but had hypertension of severity (152 +/- 13/95 +/- 11 mg Hg) similar to the 79 normal-renin patients (42 +/- 14 years; 152 +/- 17/98 +/- 12 mg Hg) and 20 low-renin patients (49 +/- 13 yrs; 157 +/- 17/95 +/- 11 mm Hg). Left ventricular (LV) mass index (normal = 70 +/- 25 g/m2) was similar in the high- (113 +/- 21 g/m2, p less than 0.001), normal = (114 +/- 31 g/m2, p less than 0.001), and low-renin patients (115 +/- 18 g/m2, p less than 0.01). End-diastolic relative wall thickness (nl = 0.32 +/- 0.05) was equally elevated in high- (0.41 +/- 0.09), normal (0.42 +/- 0.08) and low-renin groups (0.41 +/- 0.08) (all p less than 0.001). In the entire population, there was a closer correlation of relative wall thickness with total peripheral resistance (r = 0.54, p less than 0.001) than with mean blood pressure (r = 0.31, p less than 0.05). LV dysfunction (LV fractional systolic shortening less than 26%) occurred only in two high-renin patients, whereas LV fractional shortening was significantly increased in the low-renin subgroup (p less than 0.01). We conclude that the degree of LVH is similar in low-, normal-, and high-renin hypertensives and is proportional to the degree of hypertension, even though the high-renin patients were significantly younger; but that the low-renin patients with similar level of blood pressure, even though significantly older and with a longer duration of hypertension than the other patient groups, manifest increased LV function compared to normals.

Hemodynamic effects of captopril in patients with severe chronic heart failure

The hemodynamic effects of captopril (SQ 14225), an oral inhibitor of angiotensin-converting enzyme, were measured in 10 patients with severe chronic heart failure poorly controlled by digitalis and diuretics. After administration of a 25 mg dose, the cardiac index increased from 1.82 +/- 0.14 to 2.28 +/- 0.30 liters/min/m2 (p less than 0.05) while pulmonary capillary wedge pressure decreased from 22.7 +/- 2.0 to 14.7 +/- 4.7 mm Hg (p less than 0.05). Mean blood pressure and systemic vascular resistance decreased from 85.7 +/- 6.7 to 71.2 +/- 12.0 mm Hg (p less than 0.001) and from 1,909 +/- 246 to 1,362 +/- 347 dynes-s-cm5 (p less than 0.001), respectively. Heart rate did not change significantly. There was an inverse relation between maximal augmentation in cardiac index and maximal reduction in pulmonary capillary wedge pressure (r = -0.82, p less than 0.01). While most patients demonstrated a constant hemodynamic benefit after repeated administration of captopril, some exhibited a triphasic response with attenuation of effects after the second dose and restoration of effects after the third dose. These hemodynamic benefits were observed in patients with stable chronic heart failure whose plasma renin activity was within normal range (1.1 to 7.3 ng/ml/hour).

Long-term efficacy of captopril in renovascular and essential hypertension

Captopril was used in primary and long-term treatment of 40 treatment-resistant hypertensive patients. Of these, 21 had renovascular hypertension, seven unilateral and fourteen bilateral, and 19 had essential hypertension, 10 with high-renin and 9 with normal-renin profiles. All patients were off treatment when started on captopril therapy and were treated for at least 12 months, on the average for more than 2 years. The strategy of systematic drug withdrawal used to find the lowest effective dose of captopril led to average doses of 150 to 300 mg/day. A diuretic agent was added in 17 of the 40 patients when diastolic pressure remained greater than 105 mm Hg and a beta-adrenergic blocking agent was added for tachycardia or additional pressure control in 16 patients. Captopril alone was effective in 14 of the 40 patients. In all groups, mean supine and standing blood pressure levels were maintained at less than 140/90 mm Hg without evidence of decreased effectiveness over time. Control and treatment systolic pressures were higher in patients older than 50 years. For patients of all ages, systolic but not diastolic pressure during captopril treatment was higher in the supine position than standing. Plasma renin activity remained significantly elevated over time and aldosterone excretion usually decreased despite concurrent diuretic therapy. Captopril alone or in combination with a diuretic or beta-adrenergic blocking agent is effective in long-term treatment of drug-resistant renovascular and essential hypertension.

Ultrastructural study of cholestasis induced by longterm treatment with estradiol valerate. II. Gap junctional analysis

Treatment of male Wistar rats with estradiol valerate induced alterations in hepatic gap junctions as visualized by the freeze-fracture technique. The alterations involved the spacing, and regularity of packing of the membrane particles of the P face (PF) and complementary pits on the E face (EF), as well as internalization and changes in the number, size and shape of the junctional domains. In approximately 20% of the PF's of the lateral membrane of treated animals the nonjunctional IMPs were aggregated, while the bile canalicular membrane was never involved, maintaining its random distribution of particles. It is proposed that the changes in junctional area and the more general arrangement of the junctional particles may indicate a decrease in coupling between hepatocytes. The invaginations of gap junctions may represent a means for removing gap junctional membrane from the surface or may be an expression of a higher turnover of gap junctions. We assume that the alterations observed here are due to the specific effects of estrogen. This study addresses in detail a number of possible sites of activity and modes of action for estrogen.