Effects of the calcium antagonist felodipine on the sympathetic and renin-angiotensin-aldosterone systems in essential hypertension

Studies were performed in 10 male patients with untreated essential hypertension, WHO grade I-II, aged 25-62 years, to explore the acute (single dose) and long-term (8 weeks) effects of felodipine on sympathetic activity--evaluated by plasma and urinary catecholamines--as related to blood pressure, heart rate and the activity in the renin-angiotensin-aldosterone system. The patients were hospitalized for 8 (acute) and 6 (long-term) days and were maintained on a standardized daily intake of sodium (150 mmol), potassium (75 mmol) and water (2,500 ml). Acute felodipine administration (10 mg) significantly reduced blood pressure and increased heart rate. Plasma and urinary noradrenaline, plasma renin activity and angiotensin II increased, whereas plasma and urinary adrenaline, dopamine, aldosterone and plasma vasopressin were unaltered. Long-term felodipine treatment, 10 mg twice daily, reduced blood pressure to a similar extent as acute felodipine administration, but heart rate was not significantly changed. Plasma noradrenaline 3 and 12 hours after the last dose and urinary noradrenaline were increased, whereas plasma and urinary adrenaline and dopamine were unchanged. Plasma renin activity and angiotensin II were increased 3 hours, but unchanged 12 hours after the last dose. Plasma aldosterone was unchanged but urinary aldosterone increased. Plasma vasopressin was unchanged. The changes in plasma noradrenaline as related to blood pressure, heart rate, plasma renin activity and angiotensin II during long-term felodipine treatment may reflect decreased cardiac and renal beta-adrenoceptor-mediated responses. Increased renal clearance of aldosterone could partly explain the unaltered plasma aldosterone level in spite of increased plasma angiotensin II following long-term felodipine treatment.

Effect of upright tilting on kinins as compared to renin activity in the renal venous blood from patients with essential hypertension

The effect of tilting on the release of renal kallikrein as compared to renin was studied by the determination of kinin concentration and plasma renin activity (PRA) in the renal veins in supine position and after 15 min of 45 degrees upright tilting in 10 patients with essential hypertension. Kinin concentration decreased from 0.62 +/- 0.05 microgram/1 (mean +/- S.E.M.) in supine position to 0.51 +/- 0.05 after tilting (p less than 0.01), while PRA increased from 2.84 +/- 0.39 microgram/1/3 h tpo 4.87 +/- 0.66 (p less than 0.001). These results indicate that tilting diminishes the release of renal kallikrein. It is suggested that decreased intrarenal generation of kinins may be of importance for the reduction of diuresis and natriuresis induced by tilting.

Calcium influx blockers in the treatment of essential hypertension

Elevated vascular resistance is the key factor in most cases of essential hypertension. Vascular resistance is determined by the sarcoplasmatic concentration of free Ca2+. Experimental studies have shown an increased dependence for the noradrenaline-induced contraction on extracellular Ca2+ from the aorta to the small resistance vessels. This is in accordance with the potent vasodilating effect found with Ca2+-influx inhibitors in man. Furthermore, a selective enhancement of the vasodilating response to verapamil has been found in patients with essential hypertension as compared to normotensive subjects. The verapamil-induced vasodilation in the hypertensive patients was positively correlated to plasma adrenaline concentration. These findings suggest accentuated Ca2+-influx dependent vasoconstriction in essential hypertension, which is related to the activity of the sympathetic nervous system. Acute administration of verapamil and nifedipine results in a distinct fall in blood pressure in patients with essential hypertension but not in normotensive subjects. Generally, the percentage fall in blood pressure with Ca2+-channel blockers has been closely positively correlated to the initial blood pressure level and in an open study with 43 patients with essential hypertension the decrease in blood pressure to verapamil was also positively correlated to the age of patients. These data may provide the basis for a new treatment concept for essential hypertension proposing a Ca2+-channel blocker as the first choice for the older patients and a beta-adrenoceptor blocking agent as the first line drug for the younger patients. Combined treatment with a beta-adrenoceptor blocking agent and a Ca2+-channel blocker seems most efficient in normalizing blood pressure in many therapy-resistant hypertensive patients.

Renal venous output of kinins in patients with hypertension and unilateral renal artery stenosis

In four patients with hypertension and angiographically pronounced unilateral renal artery stenosis, kallikrein activity was estimated in each kidney separately by the determination of kinin output in the renal veins. All patients showed suppression of renin release from the kidney with a non-stenotic artery. Accordingly, plasma flow from the kidney with artery stenosis could be estimated. The ratio of venous output of kinins between the kidney with a non-stenotic artery and the one with artery stenosis was 2.6-6.5. This indicates that renal artery stenosis leads to diminished intrarenal kinin generation. Reduced kinin formation may explain the low diuresis and natriuresis found in the kidney with artery stenosis.

Chlorpropamide-alcohol flushing and blood kinins

In a pilot study six patients with noninsulin dependent diabetes, three positive and three negative to chlorpropamide-alcohol flushing (CPAF), were tested. The patients were tested both without and with chlorpropamide premedication. Blood kinin concentrations were determined before and after ingestion of small quantities of alcohol. No rise in blood kinin concentrations were found during the flush suggesting that kinins do not play a major part in chlorpropamide-alcohol flushing.

Effects of estrogen replacement therapy on abdominal fat compartments as related to glucose and lipid metabolism in early postmenopausal women

The effects of estrogen replacement therapy on lipid and glucose metabolism as related to abdominal fat distribution were investigated in fifty-one healthy postmenopausal women aged 52-53 years. They were randomized to treatment with either estradiol 2 mg or placebo daily for three months in a double-blind design. Forty-six women continued with estradiol for another nine months in an open design with the addition of medroxyprogesterone for ten days every three months. Intra-abdominal and subcutaneous abdominal fat, and intrapelvic and subcutaneous pelvic fat was estimated by computed tomography before and after one year of estrogen treatment. Euglycemic hyperinsulinemic clamp, oral glucose tolerance test and analyses of blood lipids were performed after 3 and 12 months of treatment. Estrogen replacement therapy decreased body fat mass as well as intra-abdominal and intrapelvic fat, but not the subcutaneous fat compartments. LDL cholesterol decreased and HDL cholesterol increased, whereas triglycerides were not changed by one year of estrogen treatment. Insulin sensitivity and glucose tolerance were not affected by estrogen treatment. In postmenopausal women estrogen treatment for one year decreased intra-abdominal and intrapelvic fat compartments, but this was not related to changes in plasma lipid levels. Insulin sensitivity and plasma triglycerides were not affected by estrogen treatment.

Insulin sensitivity with respect to glucose metabolism in hypertension-prone men did not predict the blood pressure increase in 5 years

OBJECTIVES

To evaluate peripheral insulin stimulated glucose uptake as a predictor for increase in blood pressure in hypertension-prone men.

DESIGN

A follow-up study 5 years after a primary investigation that included an euglycaemic hyperinsulinaemic clamp to evaluate insulin sensitivity.

SUBJECTS

Thirty-two men with a family history of hypertension (relatives) and 22 men with no hypertension in the family (controls). All were normotensive and had a normal glucose tolerance.

MAIN OUTCOME MEASURES

Change in blood pressure over 5 years and its relation to the values obtained in the basal investigation.

RESULTS

Systolic and diastolic blood pressure increased in both groups during the 5 years, but diastolic blood pressure increased more in relatives than in controls (11 mm Hg vs 5 mm Hg, P = 0.03). The change in diastolic blood pressure was correlated to basal BMI (r = 0.43, P = 0.02) only in controls. There were no correlations between the change in blood pressure during the 5 years and basal glucose disposal nor to any of the other basal parameters in either relatives or controls.

CONCLUSIONS

Insulin sensitivity did not predict the change in blood pressure during the 5 years either in hypertension-prone men or in controls, nor did anthropometrical measurements, basal and stimulated insulin and maximal oxygen uptake. The blood pressure increase was related to basal BMI only in controls.

Hormone replacement therapy in healthy postmenopausal women: a randomized, placebo-controlled study of effects on coagulation and fibrinolytic factors

OBJECTIVES

To evaluate effects of postmenopausal hormone replacement therapy (HRT) on von Willebrand factor, factor (F)VIII, factor (F)VII, fibrinogen, antithrombin (AT) III, prothrombin fragments 1 and 2, protein C, total and free protein S, plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and resistance to activated protein C.

DESIGN

Part 1: double blind randomized trial for 3 months. Part 2: open study for 9 months.

SETTING

Department of Endocrinology, University Hospital, Malmö, Sweden.

SUBJECTS

Fifty-one postmenopausal women with a history of amenorrhoea of at least 6 months and body mass index > or = 24 kg m-2 participated in part 1 and 46 participated in part 2.

INTERVENTION

Randomization for placebo (n=24) or HRT (n=27). HRT was given as 2 mg oestradiol valerate for the first 3 months, with the addition of 10 mg medroxyprogesterone for 10 days every third month thereafter.

MEASUREMENTS

At baseline and after 3 and 12 months.

RESULTS

During 0-3 months in the HRT group, FVII increased (P < 0.01), whereas fibrinogen, AT III and total protein S all decreased (P < 0.001 for all). Changes in variables were expressed as Delta-values. After 3 months Delta-values differed between groups for fibrinogen (P < 0.05), AT III (P < 0.001), total protein S (P < 0.001), and PAI-1 (P < 0.001). During 0-12 months, fibrinogen, total protein S, tPA (P < 0.01 for all) and AT III (P < 0.05) decreased. In the control group, all variables were unchanged during the study, except for increases (P < 0.05) in total protein S after 3 and 12 months, and a decrease (P < 0.01) in FVIII after 12 months. After 12 months Delta-values differed for fibrinogen (P < 0.05), AT III (P < 0.05) and total protein S (P < 0.001).

CONCLUSIONS

Unopposed oestrogen substitution was associated with both potentially beneficial effects, such as decreases in fibrinogen, and potentially thrombogenic effects such as decreasing AT III and protein S and increasing FVII. During prolonged follow-up and addition of progesterone, differences between groups concerning FVII were attenuated. These data suggest that effects of HRT upon coagulation are most pronounced early after institution of unopposed treatment.

Metaiodobenzylguanidine (MIBG) scintigraphy and computed tomography (CT) in clinical practice. Primary and secondary evaluation for localization of phaeochromocytomas

OBJECTIVE

To determine the diagnostic value of metaiodobenzylguanidine (MIBG) scintigraphy compared with computed tomography (CT) for the localization of phaeochromocytomas in clinical practice.

DESIGN

Retrospective comparison between MIBG scintigrams and CT for localization of phaeochromocytomas in all patients successively examined with MIBG scintigraphy in Malmö from 1984 until January 1997.

SETTING

Malmö University Hospital, Sweden.

SUBJECTS

Sixty-four patients with clinically suspected phaeochromocytomas.

MAIN OUTCOME MEASURES

MIBG scintigrams and CTs classified as positive or negative based on original interpretations (primary evaluation) and in a secondary evaluation by one blinded examiner are assessed through histological confirmation or clinical rule out of phaeochromocytomas.

RESULTS

Twenty-five patients had surgically removed phaeochromocytomas. The remaining 39 patients had no proof of phaeochromocytomas. In the secondary evaluation, sensitivity for MIBG scintigraphy was 88% (22/25) and for CT was 100% (25/25). The specificity for MIBG scintigraphy was 89% (35/39) but only 50% for CT (18/36). Two out of a total of six extra-adrenal tumours were amongst the false-negative MIBG scintigrams.

CONCLUSIONS

MIBG scintigraphy for the localization of phaeochromocytomas is superior to CT as far as specificity, whereas CT has a higher sensitivity. After biochemical diagnosis, CT will detect most phaeochromocytomas. MIBG scintigraphy can be of value in patients who show inconclusive results with biochemical testing and CT.

Relationship between abdominal fat compartments and glucose and lipid metabolism in early postmenopausal women

The relationships between abdominal and pelvic fat compartments and glucose and lipid metabolism were investigated in early postmenopausal women. Fifty-five healthy, postmenopausal women aged 52-53 yr participated in the study. Fat distribution (intra-abdominal and sc abdominal fat, and intrapelvic and sc pelvic fat) was estimated by computed tomography. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp. In a multiple regression analysis, the size of the intra-abdominal fat compartment was the only significant predictor of insulin sensitivity (r(2) = 24%; P = 0.0002). Plasma triglycerides were closely related to the size of the intra-abdominal fat compartment (r(2) = 26%; P < 0.0001), whereas plasma free fatty acid concentrations only correlated to the size of the sc abdominal fat compartment (r(2) = 18.5%, P = 0.001). In early postmenopausal women the amount of the intra-abdominal fat strongly influences insulin sensitivity and plasma triglyceride levels, whereas plasma free fatty acids are closely related to the amount of the sc abdominal fat. Accordingly, from a metabolic standpoint it seems most essential to reduce intra-abdominal fat in postmenopausal women.

Association between a variant in the 11 beta-hydroxysteroid dehydrogenase type 2 gene and primary hypertension

The enzyme 11 beta-hydroxysteroid dehydrogenase type 2 (11BHSD2) converts cortisol to cortisone in the kidney, thereby protecting the mineralocorticoid receptor from the mineralocorticoid actions of cortisol. The syndrome of Apparent Mineralocorticoid Excess (AME), a rare monogenic form of early onset hypertension with autosomal recessive inheritance, is caused by homozygous or compound heterozygous loss of function mutations in the 11BHSD2 gene. Association has been reported between a microsatellite marker flanking the 11BHSD2 gene (D16S496) and primary hypertension. The aim of this study was to identify variants in the 11BHSD2 gene and to test if such variants or the D16S496 are associated with primary hypertension, in Swedes. To address this, the coding sequences of the 11BHSD2 gene was screened for mutations in 20 patients with primary hypertension with single strand conformation polymorphism and direct DNA sequencing techniques. A polymorphism was identified in exon 3; G534A (Glu178Glu). This polymorphism and the D16S496 microsatellite were tested for association with primary hypertension in a population consisting of 292 patients with primary hypertension and 263 normotensive control subjects. The frequency of G534G homozygotes was higher in patients with primary hypertension than in normotensive control subjects (92.8% vs 87.8%; P < 0.05). The allele frequencies of the D16S496 microsatellite did not differ between the two groups (chi(2) = 11.0, df = 10; P = 0.36). In conclusion, over-representation of individuals homozygous for the G534 allele in hypertensive patients compared with control subjects suggests that a mutation in linkage disequilibrium with the G534A polymorphism could increase susceptibility to primary hypertension. Journal of Human Hypertension (2000) 14, 819-823

Genetic variants of thiazide-sensitive NaCl-cotransporter in Gitelman's syndrome and primary hypertension

Gitelman's syndrome is an autosomal recessive disorder characterized by electrolyte disturbances and low blood pressure. The disease is caused by homozygous or compound heterozygous inactivating mutations in the thiazide-sensitive NaCl-cotransporter gene leading to reduced renal sodium reabsorption. We report 4 patients with Gitelman's syndrome from southern Sweden, all in whom we identified compound heterozygous mutations in the thiazide-sensitive NaCl-cotransporter gene (Gly439Ser, Gly731Arg, Gly741Arg, Thr304Pro, and 2745insAGCA), of which the latter 2 have not been described before. We hypothesized that such mutations in their heterozygous form protect against primary hypertension in the general population and that the gene may also harbor activating mutations that increase the risk for primary hypertension. Accordingly, the gene was screened for mutations in 20 patients with primary hypertension and in 20 normotensive subjects by single-strand conformation polymorphism and direct DNA sequencing. The Arg904Gln, Gly264Ala, and C1420T variants, found in the mutation screening of subjects without Gitelman's syndrome, were studied further. Population genotype frequencies were determined in 292 unrelated patients with primary hypertension and 264 unrelated normotensive subjects from southern Sweden. Gln904 homozygotes were overrepresented in hypertensive patients compared with normotensive subjects (5 of 292 versus 0 of 264; P:=0.03). In conclusion, we confirm that Gitelman's syndrome is caused by mutations in the thiazide-sensitive NaCl-cotransporter gene. Our results further suggest that subjects homozygous for the Gln904 variant have an increased risk for development of primary hypertension.

Hormone replacement therapy in healthy postmenopausal women. Effects on intraplatelet cyclic guanosine monophosphate, plasma endothelin-1 and neopterin

OBJECTIVES

To evaluate beneficial effects of postmenopausal hormone replacement therapy (HRT) on endothelial function, measured as intraplatelet cyclic guanosine monophosphate (cGMP, mediator of nitric oxide), cyclic adenosine monophosphate (cAMP, mediator of prostacyclin) and plasma endothelin-1 (ET-1), and on monocyte activation, measured as plasma neopterin.

DESIGN

Part 1: double-blind randomized trial for 3 months; part 2: open study for 9 months.

SETTING

The study was performed at the Department of Endocrinology, University Hospital, Malmö, Sweden.

SUBJECTS

Fifty-one postmenopausal women participated in part 1 and 46 in part 2. Inclusion criteria included a history of amenorrhoea for at least 6 months before the study and body mass index >/= 24 kg m-2.

INTERVENTION

Randomization for either placebo (n = 24) or HRT (n = 27). HRT was given as 2 mg oestradiol valerate for the first 3 months with the addition of 10 mg medroxyprogesterone for 10 days every third month thereafter.

MEASUREMENTS

Performed at baseline and after 3 and 12 months of the study.

RESULTS

In the HRT group, intraplatelet cGMP increased from 0.56 (0.35-0.94) to 0.61 (0.42-3. 40) and 0.65 (0.43-1.08) pmol (109 platelets)-1 after 3 and 12 months, respectively (P = 0.01), whereas plasma ET-1 decreased from 3.2 (1.1-6.8) to 2.0 (0.8-5.1) and 1.8 (0.4-15.4) pg mL-1 (P < 0. 001). Intraplatelet cAMP and plasma neopterin were unchanged. When smokers (n = 15) and non-smokers (n = 12) in the HRT group were analysed separately, significant effects were seen only amongst smokers. The control group showed unchanged levels of cGMP, cAMP, ET-1 and neopterin.

CONCLUSIONS

These data suggest beneficial effects of HRT on endothelial function which may account for anti-atherogenic effects of HRT in postmenopausal women, especially in smokers. No effects of HRT were seen upon monocyte activation.

Effect of salt on insulin sensitivity differs according to gender and degree of salt sensitivity

The aim of the present study was to investigate the effect of salt intake on insulin sensitivity and the relation between salt sensitivity and insulin sensitivity in genetically hypertension-prone individuals. Twenty-eight healthy subjects (13 men and 15 women) with a family history of hypertension were examined at baseline, after 1 week of salt restriction (10 mmol/d), and after 1 week of salt loading (240 mmol/d). Insulin sensitivity was measured with the hyperinsulinemic euglycemic clamp after the low- and high-salt diets. Salt sensitivity was defined as the difference in mean arterial blood pressure between the high-salt and the low-salt diets. There was no significant relationship between insulin sensitivity and salt sensitivity after either of the 2 diets. In the men, salt sensitivity was inversely related to plasma renin activity (r=-0.61, P=0.03) and plasma aldosterone (r=-0.74, P=0.004), whereas salt sensitivity in women was directly correlated with the salt-induced increase in body weight (r=0.68, P=0.005). In men, the high-salt diet induced a change in glucose disposal that was strongly correlated with the degree of salt sensitivity (r=0.83, P=0. 0004), plasma renin activity (r=-0.82, P=0.0006), and plasma aldosterone concentrations (r=-0.87, P=0.00009) (eg, the greater the salt sensitivity and the lower the activity of the renin-angiotensin-aldosterone system, the greater improvement in insulin sensitivity). No such relationships were observed in women. In conclusion, increased salt sensitivity and decreased activity of the renin-angiotensin-aldosterone system predict improved insulin sensitivity with high-salt intake compared with low-salt intake in men, suggesting an interaction among salt intake, salt sensitivity, the renin-angiotensin-aldosterone system, and insulin action.

Role of the Gly460Trp polymorphism of the alpha-adducin gene in primary hypertension in Scandinavians

Previous studies have suggested that the Trp460 allele of the Gly460Trp polymorphism in the alpha-adducin gene is associated with salt sensitivity and primary hypertension. The present study was undertaken to evaluate if the Trp460 allele of this polymorphism is associated with primary hypertension in Scandinavians. To address this issue, 294 patients with primary hypertension and 265 normotensive control subjects from Sweden were examined and genotyped for the Gly460Trp polymorphism using polymerase chain reaction and restriction fragment length polymorphism methods. We then used a population of 80 patients with primary hypertension and 154 normotensive control subjects from Finland to replicate the findings. The frequency of the Trp460 allele was lower in hypertensive patients than in normotensive controls in the Swedish population (17.7% vs 23.0%; P = 0.03) and in the Finnish population (14.4% vs 19.5%; NS). Therefore we also performed a pooled analysis in which the frequency of the Trp460 allele was significantly lower in hypertensive patients than in normotensive controls (17.0% vs 21. 7%; P = 0.02). In subjects who did not receive antihypertensive medication (n = 447) there was no difference between carriers of the three different codon 460 genotypes (Trp-Trp; Trp-Gly and Gly-Gly) either for systolic (128 +/- 18; 127 +/- 15 and 129 +/- 17 mm Hg, NS) or for diastolic blood pressure (75.6 +/- 12.1; 74.7 +/- 9.3 and 75.0 +/- 10.4 mm Hg, NS). In conclusion, the lower frequency of the Trp460 allele in hypertensive patients than in normotensive controls strongly argues against a pathogenic role of this allele in primary hypertension. The results rather suggest that another variant in linkage disequilibrium with the Gly460Trp polymorphism increases susceptibility for hypertension. Journal of Human Hypertension (2000) 14, 43-46.

Heredity for hypertension influences intra-uterine growth and the relation between fetal growth and adult blood pressure

OBJECTIVE

To study whether heredity for hypertension influences intra-uterine growth and the relationship between fetal growth and adult blood pressure.

DESIGN

Five-year prospective follow-up study with retrospective collection of data on size at birth and gestational age from obstetric records.

SETTING

Centre of preventive medicine in Malmo, Sweden.

SUBJECTS

Thirty normotensive men with and 27 without heredity for hypertension were investigated in 1990, and the majority (n = 28 and n = 20, respectively) in 1995 also.

MAIN OUTCOME MEASURES

Two measures of intra-uterine growth were compared between the groups and related to adult systolic blood pressure: the birth weight deviation from the expected birth weight based on ultrasonically derived intra-uterine growth curves, and the degree of thinness at birth (ponderal index = weight/length3).

RESULTS

The birth weight deviation in men with heredity for hypertension differed significantly from that in men without such heredity (%) (-6.9+/-12.0 versus +7.3+/-18.4; P = 0.002). Ponderal index was somewhat lower in the men with than in those without heredity for hypertension, but the difference did not reach statistical significance (kg/m3) (25.9+/-2.6 versus 27.0+/-2.2; P = 0.08). In the group with heredity for hypertension, systolic blood pressure correlated inversely with ponderal index both in 1990 (r = -0.44; P = 0.01) and 1995 (r = -0.49; P = 0.009), and the 5-year increase in systolic blood pressure correlated inversely with the birth weight deviation (r = -0.38; P = 0.04). No such correlations were found in the group without heredity for hypertension.

CONCLUSION

Our results suggest that genetic factors contributing to the development of hypertension may influence intra-uterine growth.

Reduced transcapillary fluid absorption from skeletal muscle and skin during hypovolaemia in insulin-dependent diabetes mellitus

OBJECTIVES

Diabetes mellitus is associated with a high cardiovascular morbidity which has been linked to disturbances in microvascular function. This study was designed to examine the transcapillary fluid absorption during experimental hypovolaemia in type 1 diabetes.

SUBJECTS

Twelve males with type 1 diabetes (age 25 +/- 3 years, duration 8 +/- 1 years) with no clinical microangiopathy and 12 healthy males (22 +/- 2 years).

INTERVENTIONS

As a model for hypovolaemic circulatory stress, lower body negative pressure (LBNP: 15, 30 and 60 cmH2O) was used. Transcapillary fluid absorption from tissue to blood in the upper arm, as well as forearm blood flow, was measured by volumetric technique.

RESULTS

Resting forearm blood flow, heart rate and blood pressure were similar in diabetic patients and controls. Basal plasma noradrenaline was reduced in the diabetics compared with controls (0.75 +/- 0.06 vs. 1.09 +/- 0.10 pmol L-1, P < 0.05), but the increase in plasma noradrenaline in response to LBNP was similar in the two groups. The haemodynamic responses to LBNP in the two groups were equal, showing a reduction of pulse pressure, an increase in heart rate and in peripheral resistance with a concomitant blood flow reduction. The transcapillary fluid absorption (mL 100 mL-1 min-1) was significantly reduced in the diabetic patients: LBNP 15 cmH2O, 0.024 +/- 0.004 vs. 0.036 +/- 0. 002; 30 cmH2O, 0.041 +/- 0.003 vs. 0.056 +/- 0.005; and 60 cmH2O, 0. 057 +/- 0.007 vs. 0.091 +/- 0.008 (diabetic patients vs. controls, P < 0.001).

CONCLUSIONS

The transcapillary fluid absorption from tissue to blood during hypovolaemic circulatory stress in type 1 diabetic patients is reduced by one-third compared with controls, which indicates impaired plasma volume regulation. This basic mechanism for plasma volume control is affected before clinical microcirculatory complications are found and could be one of the causes of the increased cardiovascular morbidity and mortality in IDDM.

Increasing neopterin and decreasing endothelin-1 in plasma during insulin infusion in women

Leukocyte-derived inflammatory mediators and endothelial production of vasoconstrictive factors, such as endothelin-1, and vasodilatory and platelet anti-aggregatory factors, such as nitric oxide (NO) and prostacyclin (PGI2), may have a role in the pathogenesis of atherosclerosis. In this study we evaluated whether insulin affects the monocyte-derived inflammatory mediator neopterin and endothelin- in plasma (p), and NO and PGI2 mediators cyclic 3'-5' guanosine monophosphate (cGMP) and cyclic 3'-5' adenosine monophosphate (cAMP) in platelets. P-neopterin was measured by enzyme linked immunosorbent assay (ELISA), and p-endothelin-1, intraplatelet cAMP and cGMP were measured by radioimmunoassay (RIA) before and after euglycaemic hyperinsulinaemic clamping in 51 healthy postmenopausal women aged 53-54 years. "Placebo clamping" with NaCl infusion was performed in a subgroup of 5/51 women. During euglycaemic hyperinsulinaemic clamping, p-endothelin-1 decreased (from 3.3+/-0.2 pg/ml to 2.4+/-0.2 pg/ml; p<0.01), whereas p-neopterin (from 5.0+/-1.1 nmol/l to 6.2+/-1.4 nmol/l; p<0.001) and both intraplatelet cGMP (from 0.61+/-0.03 to 0.68+/-0.03 pmol/10(9) platelets; p<0.05) and cAMP (from 4.00+/-0.14 to 4.76+/-0.20 pmol/10(9) platelets; p<0.001) increased. Increases in cGMP (from 0.79+/-0.05 to 1.07+/-0.15 pmol/10(9) platelets; p = 0.14) and cAMP (from 4.76+/-0.15 to 5.52+/-0.36 pmol/10(9) platelets; p = 0.08) also occurred during NaCl infusion, whereas neopterin and endothelin-1 values were unchanged. In conclusion, insulin administration was associated with decreasing p-endothelin-1 levels and increasing levels of p-neopterin and intraplatelet cyclic nucleotides in accordance with vasodilatation and monocyte activation.

Angiotensin converting enzyme inhibition and calcium antagonism attenuate streptozotocin-diabetes-associated mesenteric vascular hypertrophy independently of their hypotensive action

OBJECTIVES

To investigate the relative roles of angiotensin II, bradykinin, and calcium-dependent pathways in the genesis of mesenteric vascular hypertrophy in experimental diabetes.

DESIGN

Streptozotocin-induced diabetic Sprague-Dawley rats were randomly allocated to these treatments for 24 weeks: no treatment; ramipril at a hypotensive dose; ramipril plus the bradykinin type 2 receptor blocker icatibant; icatibant alone; ramipril at a low dose; the angiotensin II type 1 receptor antagonist, valsartan; the dihydropyridine calcium antagonist, lacidipine; and the nondihydropyridine calcium antagonist mibefradil.

METHODS

Systolic blood pressure was serially measured every 4 weeks by tail-cuff plethysmography. We assessed the vascular architecture in sections of mesenteric arteries obtained after in-vivo perfusion, which were stained with an antibody to alpha-smooth muscle actin.

RESULTS

Both blood pressure and the mesenteric arterial wall: lumen ratio were reduced by administration of ramipril, at the high dose, either alone or in combination with icatibant, and also by valsartan. Treatment either with the low dose of ramipril or with the calcium antagonists lacidipine and mibefradil was associated with a decrease in the wall : lumen ratio of the mesenteric arteries without influencing blood pressure.

CONCLUSIONS

These findings demonstrate that blockade both of angiotensin II-dependent and of calcium-dependent pathways attenuates mesenteric vascular hypertrophy in experimental diabetes. Furthermore, the antitrophic effects of these antihypertensive agents may be independent of their hypotensive effects.

Mutations and variants of the epithelial sodium channel gene in Liddle's syndrome and primary hypertension

Liddle's syndrome is a rare monogenic form of hypertension caused by truncating or missense mutations in the C termini of the epithelial sodium channel beta- or gamma-subunits. These mutations delete or alter a conserved proline-rich amino acid sequence referred to as the PY-motif. We report here a Liddle's syndrome family with a betaArg564X mutation with a premature stop codon deleting the PY-motif of the beta-subunit. This family shows marked phenotypic variation in blood pressure, serum potassium levels, and age of onset of hypertension. Given the similarity with primary hypertension, changes in the C termini of the beta- or gamma-subunits may contribute to the development of primary hypertension or to hypertension associated with diabetic nephropathy. Accordingly, the coding sequences for the cytoplasmic C termini of the beta- and gamma-subunits were screened for mutations with the use of polymerase chain reaction, single-strand conformation polymorphism, and direct DNA sequencing in 105 subjects with primary hypertension and 70 subjects with diabetic nephropathy. One frequent polymorphism was identified, but its frequency did not differ among subjects with primary hypertension, subjects with diabetic nephropathy, or control subjects. Two of the 175 subjects with primary hypertension or diabetic nephropathy showed variants that were not present in 186 control subjects. None of the variants changed the PY-motif sequence. In conclusion, a betaArg564X mutation is the likely cause of Liddle's syndrome in this Swedish family, but it is unlikely that mutations in the beta- and gamma-subunit genes of the epithelial sodium channel play a significant role in the pathogenesis of primary hypertension or diabetic nephropathy.

Insulin sensitivity, sodium-lithium countertransport and platelet free calcium concentrations in normotensive men with a family history of hypertension

Peripheral glucose disposal (assessed with the euglycaemic-hyperinsulinaemic clamp technique), Na+-Li+ countertransport in erythrocytes and the cytosolic free Ca2+ concentration in platelets were determined in 36 men from families with essential hypertension in at least two close relatives and in 28 age- and weight-matched men from families without hypertension. All had diastolic blood pressure consistently below 90 mm Hg and a normal oral glucose tolerance test. The mean age of the study population as a whole was 37 years (range 24-46). Insulin sensitivity index values (glucose disposal/serum insulin concentration during the clamp) were lower in the familial hypertension group than in the control group, but the two groups did not differ in Na+-Li+-countertransport, or in the platelet cytosolic free Ca2+ concentration which was correlated to the waist: hip circumference ratio in both groups (r = 0.38 and r = 0.49, respectively). The present findings do not support the hypothesis that an increase in Na+-Li+ countertransport activity or the platelet cytosolic free Ca2+ concentration is a marker of insulin resistance in hypertension prone men.

Muscle fibre composition and glycogen synthase activity in hypertension-prone men

OBJECTIVES

To study muscle fibre characteristics and glycogen synthase activity in relation to peripheral glucose disposal in skeletal muscle in hypertension-prone men.

DESIGN

The hyperinsuliemic euglycemic clamp method was used to calculate insulin sensitivity index (M/I). Muscle biopsies were performed for the analysis of slow-twitch (ST) and fast twitch (FT, low insulin sensitivity and low capillarisation compared to ST fibres) muscle fibres, capillarisation (number of capillaries per fibre) and diffusional index (mean area per fibre divided by capillarisation) of muscle fibres, capillary density (capillaries mm(-2) muscle fibre) and glycogen synthase activity.

SUBJECTS

Thirty-two young, healthy, normotensive men with a family history of hypertension (REL) were compared to 2 5 age-matched men with no family history of hypertension (CON) and similar body mass index (BMI).

RESULTS

REL had a lower M/I (P = 0.021), lower capillarisation (P = 0.04) and a tendency of a lower diffusional index of subgroup b of FT muscle fibres (P = 0.10) compared to CON. Glycogen synthase activity did not differ between the groups.

CONCLUSIONS

Men with a family history of hypertension have less capillaries per FTb fibre and greater diffusion distance from the capillary to the muscle cell compared to controls, which may be a contributory factor to the lower insulin sensitivity in the former group. However, additional investigations are needed to study the causality in this association.

Low testosterone and insulin resistance in hypertension-prone men

The aim of the study was to elucidate the relationship between peripheral insulin sensitivity and testosterone and sex hormone binding globulin (SHBG) in the development of hypertension. An euglycaemic hyperinsulinaemic clamp was performed to determine insulin sensitivity and sex steroid hormones and SHBG were analysed in 35 normotensive men with a family history of hypertension (relatives) and 27 age and body mass index matched controls (controls). Relatives had lower concentrations of serum total testosterone and SHBG, and lower insulin sensitivity compared to controls. Free testosterone concentrations were the same in both groups. Relatives had lower maximal oxygen uptake compared to controls. Total testosterone and SHBG were correlated to basal insulin concentration and insulin sensitivity in relatives, but not in controls. In stepwise regression analysis, total testosterone explained 37% and walst circumference 6% of the variation of insulin sensitivity in relatives, and walst circumference explained 29% in controls. When substituting testosterone with SHBG in this model, SHBG explained 48% of the variation in insulin sensitivity in relatives. The finding of a closer relationship between insulin sensitivity and SHBG than between insulin sensitivity and total testosterone suggests that the SHBG level is primarily influenced by insulin sensitivity in the relatives.

Vascular hypertrophy and albumin permeability in a rat model combining hypertension and diabetes mellitus. Effects of calcium antagonism, angiotensin converting enzyme inhibition, and angiotensin II-AT1-receptor blockade

The aim of this study was to compare the effects of angiotensin converting enzyme (ACE) inhibition, angiotensin II (AII) AT1-receptor blockade, and dihydropyridine calcium antagonism on hypertrophy and on vascular albumin permeability in kidney, heart, and mesenteric artery in a model combining genetic hypertension and diabetes mellitus. Diabetes mellitus was induced by streptozotocin in 8-week-old spontaneously hypertensive rats. The animals were randomized to receive no treatment, the angiotensin converting enzyme inhibitor ramipril, the AII AT1-receptor blocker valsartan, or the dihydropyridine calcium antagonist lacidipine for 3 weeks. Vascular albumin permeability was measured as the tissue content of intravenously injected Evans blue dye (EB) in kidney, heart, and mesenteric artery and the tissue/plasma EB ratio was calculated. Systolic blood pressure was reduced by all three antihypertensive regimens. Glycemic control was similar in all diabetic groups. Kidney hypertrophy was not affected by any of the antihypertensive drugs. Hypertrophy of the mesenteric artery was enhanced by lacidipine but was not affected by ramipril or valsartan. Relative heart weight was also increased by lacidipine. Vascular albumin permeability, expressed as EB content in micrograms/gram dry weight or as tissue/plasma EB ratio, was higher in the kidneys of lacidipine-treated rats than in any other group of diabetic rats. There was a positive correlation between kidney weight/body weight and kidney/plasma EB ratio in the diabetic rats. These findings indicate that the dihydropyridine calcium antagonist lacidipine is associated with an unfavorable effect on vascular hypertrophy and on vascular albumin permeability in the kidneys in rats with hypertension and diabetes mellitus. Furthermore, there seems to be a coupling in the diabetic kidney between hypertrophy and increased vascular albumin permeability.

Coagulation and fibrinolytic factors in normotensive hypertension-prone men

OBJECTIVE

To evaluate whether a family history of hypertension is associated with disturbances in the coagulation and fibrinolytic systems.

SUBJECTS

Thirty-five normotensive men with a family history of hypertension (relatives) and 27 age- and body mass index-matched controls with a family history (controls).

METHODS

Insulin sensitivity was determined with a euglycaemic hyperinsulinaemic clamp technique. Maximal oxygen uptake was estimated from a submaximal work test. Blood samples were analysed for several coagulation and fibrinolytic factors.

RESULTS

Relatives had higher plasma levels of plasminogen activator inhibitor-1. Levels of plasma factor VII, prothrombin fragments 1 and 2, fibrinogen and von Willebrand factor antigen did not differ significantly between the groups. However, antithrombin III, protein C and protein S levels were higher in the relatives than in the controls. Coagulation and fibrinolytic factors correlated to waist circumference, insulin sensitivity, maximal oxygen uptake and serum triglycerides level.

CONCLUSIONS

Normotensive men with a family history of hypertension have an inhibited fibrinolysis, but also higher levels of several anticoagulant factors. The clinical application of these findings for the future development of cardiovascular disease warrants additional studies.

Primary antiphospholipid syndrome associated with postoperative primary adrenal failure

A 51-year-old Caucasian male without previous history of thromboembolic disease developed Coomb's positive haemolytic anaemia, thrombocytopenia, transient paranoid psychosis and bilateral adrenal haemorrhage with primary adrenal failure after surgery for inguinal hernia. The activated partial thromboplastin time was spontaneously prolonged, and lupus anticoagulant and anticardiolipin antibodies were detected. In the absence of criteria for classification of systemic lupus erythematosus (SLE), the entity was classified as a primary antiphospholipid syndrome. Despite the persistence of the serological abnormalities, the patient remains well after substitution with cortisone. Primary adrenal failure due to adrenal haemorrhage can be associated with the primary antiphospholipid syndrome.

Vascular albumin permeability and hypertrophy in a rat model combining streptozotocin-induced diabetes and genetic hypertension

OBJECTIVE

To investigate the effects of hypertension and diabetes mellitus on vascular albumin permeability and hypertrophy in 11-week-old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) with and without 3 weeks of streptozotocin-induced diabetes.

METHODS

Vascular albumin permeability was measured as tissue content of intravenously injected Evans blue dye.

RESULTS

Diabetic rats showed hypertrophy of the kidneys, and hypertensive rats showed hypertrophy of the heart. In the mesenteric artery there was an additive hypertrophic effect of diabetes and hypertension. The Evans blue content in kidneys was higher in diabetic SHR than in diabetic and in control WKY rats. The kidney: plasma Evans blue ratio was higher in diabetic SHR than in the other three groups, and the heart: plasma Evans blue ratio was higher in diabetic SHR than in control WKY rats or control SHR. The Evans blue content and tissue: plasma Evans blue ratio did not differ in aorta, mesenteric artery or skeletal muscle among the groups. There was no positive correlation between vascular albumin permeability and hypertrophy in any of the tissues studied.

CONCLUSION

There was no relationship between vascular albumin permeability and hypertrophy, but increased vascular albumin permeability was found in kidneys and hearts of rats with both diabetes and hypertension. This suggests an additive or synergistic effect of diabetes and hypertension in producing vascular changes.

Insulin and forearm vasodilation in hypertension-prone men

Insulin-stimulated peripheral glucose uptake and insulin-mediated forearm vasodilation were investigated in 38 normotensive men with a family history of hypertension (relatives) compared with 27 age- and body mass index-matched normotensive men with no family history of hypertension (control subjects). The euglycemic hyperinsulinemic clamp technique was used to measure peripheral glucose uptake (insulin sensitivity index) and the metabolic clearance rate of insulin. Intra-arterial blood pressure and forearm blood flow were determined simultaneously, and forearm vascular resistance was calculated. The insulin sensitivity index was lower in relatives than in control subjects. The metabolic clearance rate of insulin was reduced and did not correlate to glucose disposal in the relatives as opposed to the control subjects. Forearm blood flow increased and forearm vascular resistance decreased to a similar extent in the two groups during the clamp. The vasodilator response was positively correlated to glucose disposal only in the relatives. In conclusion, impaired insulin-stimulated peripheral glucose uptake in normotensive sons from hypertensive families was accompanied by retained insulin-mediated forearm vasodilation. Thus, skeletal muscle blood flow supply does not seem to be the major determinant for glucose disposal. On the other hand, the positive correlation between glucose disposal and decrease in forearm vascular resistance in the relatives suggests that insulin-mediated vasodilation may be a limiting factor for peripheral glucose uptake in insulin-resistant individuals.

Insulin and renal sodium retention in hypertension-prone men

Insulin-stimulated peripheral glucose uptake and insulin-induced renal tubular sodium reabsorption were investigated in normotensive men with a family history of hypertension (relatives, n = 35) compared with age- and body mass index-matched normotensive men with no family history of hypertension (controls, n = 23). The effect of insulin on the renin-aldosterone system was also studied. The euglycemic hyperinsulinemic clamp technique was used to measure peripheral glucose uptake (insulin sensitivity index). Renal clearance of 51Cr-labeled EDTA, sodium, and lithium was used to calculate fractional excretion of sodium and fractional proximal and distal tubular reabsorption of sodium before and during insulin infusion. The insulin sensitivity index was lower in relatives than in controls. Fractional excretion of sodium was reduced, and fractional proximal and distal tubular reabsorption of sodium were increased to the same extent in both groups during insulin infusion. Fractional distal tubular reabsorption of sodium was positively correlated to the reduction of serum potassium in all individuals. Plasma renin activity increased to the same extent in both groups, whereas plasma aldosterone was reduced only in controls. In conclusion, the impaired insulin-stimulated glucose uptake in peripheral tissues in normotensive sons of hypertensive families was accompanied by retained insulin-induced tubular sodium reabsorption. The lack of suppression of aldosterone secretion in these individuals may enhance sodium retention.

Insulin resistance is coupled to low physical fitness in normotensive men with a family history of hypertension

OBJECTIVE

To investigate insulin sensitivity and the influence of level of physical fitness in men with a family history of hypertension and in control subjects.

DESIGN

Insulin sensitivity was determined and physical fitness estimated in 39 normotensive, glucose-tolerant men with a family history of hypertension (Relatives group) and in 29 age- and body mass index-matched normotensive men with no such family history (Controls group).

METHODS

The euglycaemic hyperinsulinaemic clamp technique (steady-state insulin concentration approximately 100 mU/l) was used to determine insulin sensitivity. Physical fitness, measured as maximal oxygen uptake, was estimated from the heart rate response to a submaximal exercise test.

RESULTS

Insulin sensitivity index and estimated maximal oxygen uptake were lower in the Relatives than in the Controls. There was a positive correlation between insulin sensitivity and maximal oxygen uptake in both groups. In the Controls there was a negative correlation between insulin sensitivity and waist:hip ratio, but this relationship was not found in the Relatives.

CONCLUSIONS

The present findings indicate that reduction of insulin sensitivity precedes the development of high blood pressure and may be coupled to low physical fitness. As abdominal fat distribution seems not to be related to insulin sensitivity in subjects with a family history of hypertension, changes in muscle fibre composition or muscle glucose metabolism, or both, might explain the lower insulin sensitivity and physical fitness in the Relatives.

Acute renal tubular and hemodynamic effects of the calcium antagonist felodipine in healthy volunteers

To evaluate the renal tubular effects of felodipine in a low (1.25-mg) and a high (10-mg) dose, lithium clearance was measured and related to renal hemodynamics in 10 healthy volunteers. After felodipine (1.25 mg), mean blood pressure decreased 4 mm Hg and heart rate increased 4 beats per minute. GFR and renal hemodynamics were unaltered. Natriuresis and diuresis increased and lithium clearance and fractional excretion of lithium were unchanged as compared with placebo. Felodipine (10 mg) decreased mean blood pressure 8 mm Hg; heart rate increased 16 beats per minute, and plasma catecholamines were elevated. GFR was unaltered, whereas RBF increased and renal vascular resistance decreased. Natriuresis and diuresis were further increased, and lithium clearance and fractional excretion of lithium were elevated. In conclusion, felodipine in a low dose of 1.25 mg, which did not change renal hemodynamics, had natriuretic and diuretic effects at a predominantly postproximal tubular site, whereas a high dose of 10 mg, which increased RBF and decreased renal vascular resistance, had additional natriuretic and diuretic effects in the proximal tubule.

Antihypertensive efficacy and tolerability of enalapril and slow-release verapamil in essential hypertension: a double-blind, cross-over study

The antihypertensive efficacy and tolerability of enalapril (E) and slow-release verapamil (V) were compared in a 2-month double-blind cross-over study in 22 patients with mild to moderate essential hypertension. After 1 month, significantly lower systolic (P less than 0.01) and diastolic (P less than 0.02) blood pressures (BP) were achieved with E, 20 mg d-1, compared with V, 240 mg d-1. After 2 months of treatment, BP reductions were similar after E, 40 mg d-1, and V, 240 mg twice a day. The fall in supine mean BP after 2 months of treatment with V was significantly greater in patients aged greater than or equal to 50 years of age (P = 0.02) (median 18 mmHg) than in patients aged less than 50 years (10 mmHg). E showed similar effectiveness in both age groups. Statistical group analysis of a quality-of-life questionnaire showed no significant differences between the active drugs and the placebo. It is concluded that E and V are equally effective as antihypertensive agents, and that both drugs are well tolerated.

Acute effects of doxazosin and atenolol on smoking-induced peripheral vasoconstriction in hypertensive habitual smokers

The acute effects of selective alpha 1 inhibition with doxazosin (0.5-0.7 mg intravenously) and beta 1-blockade with atenolol (0.1 mg/kg body weight, intravenously) on smoking-induced peripheral vasoconstriction were investigated in 24 hypertensive habitual smokers. Forearm blood flow was measured by venous occlusion plethysmography and skin blood flow was estimated by thermography and laser doppler flowmetry. After the patients had smoked two cigarettes, plasma adrenaline elevations were similar under basal conditions and after drug administration; plasma noradrenaline remained unchanged. The smoking-induced increase in the heart rate was attenuated by atenolol compared with basal values. The smoking-induced increase in systolic blood pressure was more marked after atenolol and doxazosin (P less than 0.05) than before the drug administration. The smoking-induced increase in diastolic blood pressure was enhanced by atenolol (P less than 0.05) but unchanged by doxazosin. Smoking increased forearm vascular resistance under basal conditions (P less than 0.05) and after atenolol (P less than 0.01) but not after doxazosin. Similarly, skin temperature was significantly reduced by smoking under basal conditions and after the administration of atenolol (P less than 0.001) but not doxazosin. The smoking-induced reduction in skin blood flow was attenuated by doxazosin compared with atenolol (P less than 0.05). Thus, smoking-induced muscular and cutaneous vasoconstriction was inhibited by doxazosin as opposed to atenolol in hypertensive habitual smokers. This may reflect unmasked beta-adrenoceptor mediated vasodilation in addition to attenuated alpha 1-adrenoceptor mediated vasoconstriction.

Carotid artery surgery. Local versus general anaesthesia as related to sympathetic activity and cardiovascular effects

Arterial plasma catecholamines, blood pressure and heart rate were determined in 75 patients before, during and after carotid endarterectomy. Local anaesthesia given as a cervical block with skin infiltration containing 200 micrograms adrenaline was used in 28 patients (LA-group), general anaesthesia (nitrous oxide, fentanyl, isoflurane) with skin infiltration containing 200 micrograms adrenaline in 32 patients (GAs-group) and general anaesthesia without skin infiltration in 15 patients (GAo-group). In the LA-Group plasma noradrenaline (P-NA) levels were significantly higher during anaesthesia and surgery, with an increase from preanaesthesia levels (P less than 0.05). P-NA decreased from a preanaesthesia level in the GAo-group (P less than 0.01) but remained unaltered in the GAs-group. P-NA values in the GAo-group were lower than those of the GAs-group (P less than 0.001) following anaesthesia and surgery. Plasma adrenaline (P-A) increased in the LA- and the GAs-group and decreased in the GAo-group (P less than 0.001) following anaesthesia and surgery. In the LA-group P-A was similar before the skin incision and clamping but higher after declamping as compared to the GAs-group. Before the skin incision and thereafter P-A was lower in the GAo-group as compared to the other groups. There was a positive correlation between plasma catecholamines, on the one hand, and mean blood pressure and heart rate on the other. Two patients in the LA-, eight in the GAs- and seven in the GAo-group showed a hypotensive blood pressure reaction (SBP less than 100 mmHg; LA vs. GAo, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal and endocrine effects of long-term converting enzyme inhibition as compared with calcium antagonism in essential hypertension

In a double-blind, double-dummy, placebo-controlled crossover design, the renal hemodynamic and tubular effects of 2-month specific vasodilation with a converting enzyme inhibitor (enalapril, 40 mg once daily) was compared with that of a calcium antagonist (verapamil slow release, 240 mg twice daily) in 15 patients with established essential hypertension. Enalapril and verapamil treatment induced a 9% reduction in mean blood pressure (BP). Heart rate (HR) was similar after placebo (66 beats/min), enalapril (63 beats/min), and verapamil (63 beats/min). Plasma norepinephrine (P-NE) was unaltered after enalapril and verapamil as compared with placebo (0.92, 0.88, and 1.33 nM, respectively). Plasma angiotensin II and aldosterone decreased and plasma renin activity (PRA) increased after enalapril but were unaltered after verapamil. Glomerular filtration rate (51Cr-EDTA) was not altered by either enalapril or verapamil, whereas renal blood flow (125I-hippurate) was reduced 9% by verapamil. Renal vascular resistance (RVR) was unchanged after enalapril as well as verapamil. Fractional excretion of electrolytes and diuresis were unaltered and body weight was similar after enalapril, verapamil, and placebo (81.0, 82.5, and 80.2 kg, respectively). Long-term treatment with enalapril and verapamil had a comparable antihypertensive effect. Neither enalapril nor verapamil appeared to induce reflex activation of the sympathetic nervous system. Renal hemodynamic and tubular function was well preserved with both drugs without signs of sodium and water retention.

Mechanisms of action and clinical use of calcium antagonists in hypertension

Calcium antagonists are potent arterial vasodilators that do not lead to relevant chronic sympathetic reflex activation and sodium and volume retention. This favorable hemodynamic profile renders them suitable for monotherapy of hypertension in which they can reduce the calcium influx-dependent functional component of elevated vascular resistance that may be enhanced by altered vascular muscle cation handling and increased intracellular free calcium concentrations. Clinical studies have proved their efficacy, safety, and good tolerability alone or in combination with other drugs in uncomplicated hypertension in which they are particularly effective in older, low renin, and possibly, black patients. These properties and their efficacy in the treatment of severe and accelerated hypertension or hypertensive emergencies make them a valuable addition to already available drug therapy.

Serum gonadotropins in postmenopausal women after long-term verapamil treatment

The effect of long-term verapamil treatment on serum gonadotropin levels was studied in 13 postmenopausal women aged 48-73 years given verapamil 160-320 mg daily for 2-8 months. Serum luteinizing hormone and follicle stimulating hormone concentrations were unchanged during verapamil treatment [7.1 (5.8:11.0) and 24 (21:26) micrograms/L before and 8.8 (5.1:9.1) and 25 (19:31) micrograms/L following verapamil]. This suggests that chronic calcium influx inhibition has no major influence on the release of gonadotropins from pituitary cells.

Amiloride compared with nitrendipine in treatment of essential hypertension

The antihypertensive effect of amiloride was compared to that of the calcium antagonist nitrendipine in 12 patients (8 males), aged 34-62 years, with essential hypertension WHO grade I-II (mean supine blood pressure 158/103, standing 155/106 mmHg) in a double-blind placebo-controlled cross-over study design. Amiloride was given 5 mg once daily for one month followed by 20 mg twice daily for another month. Amiloride 5 mg once daily significantly reduced supine and standing DBP but not SBP (supine 151/94, standing 149/97 mmHg), whereas 10 mg once daily decreased SBP as well as DBP (supine 145/98, standing 145/101 mmHg). Nitrendipine 20 mg once daily significantly reduced supine and standing SBP and standing DBP (supine 150/97, standing 148/98 mmHg), but on 20 mg twice daily only supine SBP was significantly reduced (supine 150/99, standing 151/106 mmHg). Heart rate was transiently increased by nitrendipine 20 mg once daily and unchanged following amiloride. Plasma noradrenaline was unaltered following amiloride 10 mg once daily as well as nitrendipine 20 mg twice daily, whereas plasma renin activity and aldosterone were elevated following amiloride. Serum electrolytes, blood glucose, plasma lipids and body weight were not altered by any of the drugs. Amiloride 5-10 mg daily has a mild to moderate BP lowering effect in patients with essential hypertension. The BP reduction following nitrendipine 20 mg once daily was comparable to that of amiloride 5 mg daily. Nitrendipine 20 mg twice daily gave no additional BP decrease.

Renal effects of acute and long-term treatment with felodipine in essential hypertension

Enhanced renal vasoconstriction and renal tubular sodium reabsorption mediated by noradrenaline and angiotensin II (Ang II) have been implicated in the pathogenesis of essential hypertension. Since these effects seem to be calcium-dependent, renal haemodynamic and tubular function were studied following acute and long-term treatment with the calcium antagonist felodipine in 10 patients with essential hypertension. After acute felodipine administration mean blood pressure (MBP) decreased (from 111 to 95 mmHg; P less than 0.01), renal blood flow (RBF), estimated from hippurate clearance, increased (from 1030 to 1175 ml/min; P less than 0.01) and glomerular filtration rate (GFR) was unchanged (109 versus 112 ml/min). Fractional excretion (FE) of sodium, potassium, calcium, magnesium, chloride, bicarbonate and urate increased for 12 h. Following long-term felodipine treatment, mean blood pressure was reduced (97 mmHg; P less than 0.01) and RBF and GFR were unchanged (1032 and 114 ml/min, respectively). Fractional excretion of urate and calcium was increased for 24 h (from 5.9 to 6.9%; P less than 0.05 and from 1.1 to 1.3%; P less than 0.05, respectively). Serum urate decreased (from 377 to 347 mumol/l; P less than 0.01) whereas serum calcium was unchanged. Fractional excretion of sodium, potassium and chloride was increased between 3 and 6 h after felodipine. The renal haemodynamic findings after acute felodipine administration are indicative of a direct renal vasodilator action of felodipine which augments the autoregulatory renal vasodilation to produce an overall increase in RBF. Since GFR was unchanged, the increased renal excretion of electrolytes and urate reflects an action at the tubular level. Following long-term felodipine administration autoregulatory adjustment of RBF predominated.

Review of long-term trials with nitrendipine

The dihydropyridine calcium antagonist nitrendipine offers a pathophysiologically based antihypertensive treatment with a potent dilation of resistance vessels, increased arterial compliance, and an acute natriuretic/diuretic response. Prolonged nitrendipine treatment in essential hypertension is not associated with stimulation of the sympathetic nervous and the renin-angiotensin systems or accumulation of sodium and water. The antihypertensive effectiveness is similar to that of diuretics and beta-blockers, and the responsiveness appears to be greater in elderly and black patients. During long-term (approximately 1 year) nitrendipine treatment in mild to moderate hypertension, the blood pressure reduction is well sustained in "short-term" nitrendipine responders. In patients with severe hypertension, nitrendipine has a potent antihypertensive effect in combination with beta-blockers and/or diuretics. In mild-moderate hypertension, a single daily dose (10-40 mg) may be sufficient, whereas two daily doses (20-80 mg/day) seem necessary in severe hypertension. Common side effects are headache, flush, and palpitations (approximately 20-30%), but these are generally mild and transient. Dizziness and malaise occur in approximately 5%, often later during treatment. Peripheral edema in 5-20% of the patients is generally mild but persistent. Nitrendipine has no adverse effects on glucose and lipid metabolism or on plasma levels of electrolytes and urate. The ultimate aim of antihypertensive treatment is to prevent cardiovascular complications. As for other calcium antagonists, no study on primary prevention of cardiovascular complications in hypertension has been published. With regard to regression of left ventricular hypertrophy accompanying essential hypertension, conflicting results have been found with nitrendipine.

Hemodynamic and counterregulatory effects of calcium antagonists in hypertension

Increased systemic vascular resistance in essential hypertension depends on increased calcium influx. Calcium antagonists lower cytosolic free calcium concentrations mainly through a reduction of transmembraneous calcium influx and are potent arterial vasodilators. Dihydropyridine calcium antagonists are pharmacologically more potent with respect to arterial vasodilatation than verapamil- or diltiazem-type calcium antagonists and have less or no clinically detectable negative inotropic effects, but this seems to be of importance only in patients with reduced cardiac function. All calcium antagonists lower high blood pressure through a reduction of elevated systemic vascular resistance without clinically relevant activation of sympathetic reflexes or the renin-angiotensin-aldosteron system. However, subtle changes of sympathetic nervous system activity may codetermine the acute and chronic blood pressure response. They do not lead to volume retention because of improved intrarenal hemodynamics and a diuretic effect. Interference with angiotensin and sympathetically mediated vasoconstrictor mechanisms probably also contributes to their antihypertensive effect. This hemodynamic profile is similar for all calcium antagonists but the degree of acute sympathetic stimulation seems to be greater for dihydropyridines. Their overall favorable hemodynamic and neurohumoral profile and their proven efficacy and lack of serious side effects have made calcium antagonists a valuable addition to the armanentarium available for monotherapy of hypertension.

Glucoregulatory hormone response to insulin-induced hypoglycaemia following long-term calcium antagonism with felodipine in patients with essential hypertension

The effect of 8 weeks' treatment with the dihydropyridine calcium antagonist felodipine on glucoregulatory hormone response following insulin-induced hypoglycaemia was evaluated in 7 patients with essential hypertension, WHO grade I-II. After an iv insulin injection (0.1 IU/kg), blood glucose decrement and nadir were similar before and during felodipine treatment. Basal glucagon, noradrenaline, adrenaline, GH and cortisol levels were unchanged, and the response to insulin-induced hypoglycaemia was similar before and during felodipine treatment. Basal plasma dopamine levels were similar and did not change during insulin-induced hypoglycaemia before and during felodipine treatment. Basal serum levels of TSH, T3 and T4 were unaltered following felodipine. In conclusion, long-term treatment with felodipine did not alter the hypoglycaemic effect of exogenous insulin, or the recovery from hypoglycaemia or the glucoregulatory hormone response to insulin-induced hypoglycaemia in patients with essential hypertension.

Catecholamines, renin-angiotensin-aldosterone, and cardiovascular response during exercise following acute and long-term calcium antagonism with felodipine in essential hypertension

Studies were performed in nine patients with essential hypertension to explore the effect of the calcium antagonist felodipine on the exercise-induced responses of the sympathetic and renin-angiotensin-aldosterone systems as well as of blood pressure and heart rate. The patients were subjected to an individually graded submaximal work test (bicycling) after administration of placebo and a single dose of felodipine (10 mg) in a double-blind design and following long-term (8 weeks) felodipine treatment (10 mg twice daily). After a single dose of felodipine sitting preexercise blood pressure was decreased, whereas heart rate, plasma noradrenaline, adrenaline, renin activity, and angiotensin II increased. After long-term felodipine treatment blood pressure was reduced, heart rate was unchanged, and plasma noradrenaline and renin activity increased. The exercise-induced increases in plasma catecholamines, renin activity, angiotensin II, aldosterone, blood pressure, and heart rate were similar after acute and long-term felodipine administration as compared with placebo. In conclusion, acute and long-term felodipine treatment influences neither reflex activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system nor the cardiovascular responses to physical exercise in patients with essential hypertension.

Unchanged insulin secretion and glucose tolerance but increased insulin clearance during long-term calcium antagonism with felodipine in essential hypertension

Studies were performed to explore the effect of calcium antagonism with felodipine for 8 weeks on glucose homeostasis and serum lipids in 8 patients with essential hypertension. Fasting levels of blood glucose as well as serum C-peptide, insulin, glucagon and free fatty acids were unchanged following felodipine. During an intravenous glucose tolerance test, the incremental area under the curve for C-peptide and glucose was unchanged, but decreased for insulin, after felodipine. The decremental area over the curve for glucagon and free fatty acids remained unchanged. Fasting serum total cholesterol and high density lipoprotein cholesterol were unaltered, whereas triglycerides decreased following felodipine. The findings indicate that calcium antagonism with felodipine does not affect glucose-induced insulin release in vivo. The increased insulin clearance could be expected to be coupled to a change in glucose tolerance, but this was unaltered during long-term calcium antagonism.

The effect of 8 weeks treatment with the calcium antagonist felodipine on blood pressure, heart rate, working capacity, plasma renin activity, plasma angiotensin II, urinary catecholamines and aldosterone in patients with essential hypertension

The effect of 8 weeks treatment with the calcium antagonist felodipine--a new long-acting dihydropyridine derivative--in a dose of 10 mg twice daily was studied in 10 male patients with essential hypertension, WHO grade I-II, aged 25-62 years. Diastolic blood pressure was reduced in supine and upright position. Systolic blood pressure was reduced only in the upright position. Heart rate was unchanged in the supine and decreased in the upright position. During dynamic exercise blood pressure was reduced. The maximal working capacity decreased, whereas the maximal heart rate attained was unchanged. Twenty-four hour urinary noradrenaline excretion, plasma renin activity and 24 h urinary aldosterone excretion were increased. Plasma angiotensin II and 24 h urinary adrenaline excretion were unchanged. In conclusion, felodipine is an effective long-acting blood pressure lowering drug with minor side effects. After 8 weeks on felodipine treatment heart rate was not increased, although the activity of the sympathetic nervous system and the renin-aldosterone system seemed enhanced.

Age, race, blood pressure and renin: predictors for antihypertensive treatment with calcium antagonists

Age, race, pretreatment blood pressure and plasma renin activity have been related to the antihypertensive response to calcium antagonists in studies that included 215 patients with mild to moderate essential hypertension. Adverse effects necessitated withdrawal from therapy in about 10% of the patients. All calcium antagonists lowered blood pressure significantly and comparably without weight gain or reflex tachycardia. In a multiple linear regression analysis of 138 white patients, age, pretreatment blood pressure and renin activity were of independent and significant predictive value for the antihypertensive response. Stratification of patients into 3 age groups disclosed a greater effect in patients older than 60 years compared with those between 40 and 60 years and those below 40 years, respectively (p less than 0.01). In 16 middle-aged black patients, antihypertensive therapy with a calcium antagonist proved highly efficacious. Monotherapy with a calcium antagonist may become a first-line treatment for essential hypertension, particularly in older patients who have low renin activity and possibly in black patients as well.

Vasodilatory effect of nicardipine and verapamil in the forearm of hypertensive as compared with normotensive man

The intent of this study was to determine whether or not increased calcium-influx-mediated vasoconstriction is a primary pathogenetic disturbance in essential hypertension. Ten normotensive subjects (NT) (aged 45 +/- 12 years) and 23 patients with essential hypertension (EH) were studied. Twelve of the patients (aged 42 +/- 12 years) were classified as having mild EH and 11 patients (aged 49 +/- 11 years) as having moderate EH. Forearm blood flow and intra-arterial blood pressure were measured. Forearm vascular resistance (FVR) was calculated under basal conditions, during reperfusion following 10 min arterial occlusion, and after infusion into the brachial artery of sodium nitroprusside (0.15 and 0.6 microgram min-1 100 ml-1 tissue for 2 min each) and the calcium-influx inhibitors nicardipine (5 and 40 micrograms min-1 100 ml-1 tissue for 1 min each) and verapamil (80 micrograms min-1 100 ml-1 tissue for 1 min). FVR after 10 min arterial occlusion was lower in mild EH than in moderate EH and still lower in NT. FVR was comparable in the three groups following infusion of maximal doses of sodium nitroprusside, nicardipine, and verapamil. To allow for the vasodilator response to arterial occlusion, the decrease in FVR measured after each drug was divided by that obtained after arterial occlusion in each individual. The adjusted vasodilator response to nicardipine and verapamil, but not to sodium nitroprusside, was greater in moderate EH than in NT and mild EH. In the latter two groups the adjusted vasodilator responses were comparable.(ABSTRACT TRUNCATED AT 250 WORDS)