High plasma renin activity is combined with elevated urinary albumin excretion in essential hypertensive patients.

BACKGROUND: Several studies suggest that the hyperactivity of the circulating renin-angiotensin system might favor the progression of renal disease in essential hypertension. To elucidate this aspect, we investigated the relationship between plasma renin activity (PRA) and the urinary albumin excretion rate (UAER), an early marker of hypertension-related renal changes, in human essential hypertension. METHODS: Ninety nonobese, nondiabetic, nonhyperlipidemic patients with mild-to-moderate essential hypertension (67 males, 23 females; mean age 51.4 +/- 6.2 years) were divided into low renin (LR), normal renin (NR), and high renin (HR) subgroups according to individual PRA while they were on a constant NaCl intake (120 mmol NaCl/day). The UAER was assessed during the same NaCl intake. RESULTS: Data showed significantly higher UAER (31.3 +/- 12.9 microg/min) in HR (N = 30) than NR (N = 30, 22.7 +/- 14.4 microg/min, P < 0.02) and LR patients (N = 30, 21.7 +/- 10.8 microg/min, P < 0. 01). CONCLUSIONS: Our study demonstrates that the UAER is elevated in HR essential hypertensive patients, suggesting that high PRA accelerates the onset of early renal changes in human essential hypertension.

Angiotensin II increases the release of endothelin-1 from human cultured endothelial cells but does not regulate its circulating levels.

We investigated the effect of angiotensin II on endothelin-1 secretion in vitro and in vivo. In vivo, angiotensin II was given intravenously to 23 essential hypertensive and 8 control subjects according to different protocols: Study A, 1.0 ng x min-1 x kg-1 and 3.0 ng x min-1 x kg-1 angiotensin II for 30 min each; Study B, 1.0 ng x min-1 x kg-1 and 3.0 ng x min-1 x kg-1 angiotensin II for 120 min each; Study C, 3.0 ng x min-1 x kg-1 angiotensin II for 30 min followed by a dose increment of 3.0 ng x min-1 x kg-1 every 30 min until mean blood pressure levels increased by 25 mmHg; Study D, 1.0 ng x min-1 x kg-1 followed by 3.0 ng x min-1 x kg-1 angiotensin II for 60 min each on two different NaCl diets (either 20 mmol NaCl/day or 220 mmol NaCl/day, both for 1 week). In all in vivo studies neither plasma nor urine endothelin-1 levels changed with angiotensin II infusion. In contrast, angiotensin II (10(-9), 10(-8), 10(-7) mol/l) stimulated endothelin-1 secretion from cultured human vascular endothelial cells derived from umbilical cord veins in a time- and dose-dependent manner. The in vitro angiotensin II effects were abolished by candesartan cilexetil, an inhibitor of the membrane-bound AT1 receptor, and also by actinomycin D, an RNA synthesis inhibitor, and cycloheximide, a protein synthesis inhibitor, indicating that endothelin-1 release depended on AT1 receptor subtype and de novo protein synthesis. Our findings indicate that angiotensin II regulates endothelin-1 release by cultured endothelial cells through an AT1 receptor-dependent pathway, but does not influence circulating endothelin-1 levels in vivo.

Role of plasma and urinary endothelin-1 in early diabetic and hypertensive nephropathy.

To evaluate the role of circulating and renal endothelin-1 (ET-1) in early diabetic nephropathy, plasma ET-1 levels and urinary ET-1 excretion were evaluated in lean, normotensive patients affected by non-insulin-dependent diabetes (NIDDM) either with (n = 9, NIDDM+) or without microalbuminuria (n = 18, NIDDM-); in never-treated, lean, essential hypertensive patients with (n = 12, EH+) or without microalbuminuria (n = 10, EH-); and in healthy volunteers (n = 12). Results showed higher plasma ET-1 levels in NIDDM+ (1.97 +/- 0.58 pg/mL) than in NIDDM- (1.59 +/- 0.14 pg/mL, P = .013), EH+ (1.40 +/- 0.21 pg/mL, P = .005), EH- (0.91 +/- 0.19 pg/mL, P < .0001), and controls (0.60 +/- 0.10 pg/mL, P < .0001). The circulating ET-1 concentration was also higher in EH+ than EH- and controls (P < .0001). Urinary ET-1 excretion did not differ (P = .387, NS) between NIDDM+ (48.5 +/- 20.1 pg/min) and NIDDM- (40.9 +/- 21.6 pg/min), but was significantly reduced (P < .0001) in both groups compared with controls (70.0 +/- 15.5 pg/min). Similar findings were observed in hypertensive subgroups. No correlations were found between urinary ET-1 and other variables, including plasma ET-1 levels, in all groups. In conclusion, NIDDM+ is accompanied by a significant increase in plasma ET-1 levels. A significant elevation of circulating ET-1 concentration was evident also in NIDDM-, suggesting that early abnormalities of ET-1 production might precede the microalbuminuric phase of diabetes-related renal damage.

Early activation of vascular endothelium in nonobese, nondiabetic essential hypertensive patients with multiple metabolic abnormalities.

Circulating soluble E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular adhesion molecule-1 (VCAM-1) concentrations were evaluated in 93 nonobese essential hypertensive patients, of whom 16 had impaired glucose tolerance and hyperlipidemia (group I); 25 had impaired glucose tolerance (group II); 28 had hyperlipidemia (group III); and 24 had no metabolic abnormalities (group IV). A group of 22 healthy volunteers served as a control group. All groups were without clinical or ultrasound evidence of vascular lesion and were matched for age, sex, and BMI. Endothelial soluble adhesion molecules were measured at baseline, during an oral glucose tolerance test, and after 12 weeks of either enalapril or placebo treatments. Plasma soluble E-selectin, ICAM-1, and VCAM-1 were higher (P < 0.05) in group I and II than in the other groups (group I: E-selectin, 96.1+/-27.1; ICAM-1, 304.0+/-102.1; VCAM-1, 626.1+/-156.2 microg/l. Group II: E-selectin, 88.0+/-18.0; ICAM-1, 268.0+/-84.1; VCAM-1, 594.1+/-140.9 microg/I. Group III: E-selectin, 70.1+/-18.1; ICAM-1, 195.1+/-68.0; VCAM-1, 495.9+/-110.1 microg/l. Group IV: E-selectin, 65.1+/-16.1; ICAM-1, 168.1+/-64.0; VCAM-1, 472.1+/-108.2 microg/l). Soluble adhesins levels were not higher than normal in groups III and IV. Plasma soluble ICAM-1 concentrations increased in group I after glucose administration and were directly correlated with 2-h insulin levels (r=0.648, P=0.007). Compared with placebo, 12 weeks of enalapril treatment significantly (P < 0.0001) reduced soluble E-selectin, ICAM-1, and VCAM-1. Decrements of soluble adhesins were not dependent on enalapril-related blood pressure changes. Therefore, an early endothelial activation was present in essential hypertensive patients with impaired glucose tolerance, regardless of the presence of hyperlipidemia. ACE inhibition counteracted such endothelial activation.

Plasma endothelin-1 levels during transient acute myocardial ischaemia in men: effects of coronary revascularization.

The endothelium-derived peptide endothelin-1 (ET-1) was evaluated in 14 male patients [mean age 52.74 years (SEM 1.10)] affected by coronary artery disease during a bicycle electrocardiographic stress test and dipyridamole echocardiogram. Both tests were performed before and after coronary revascularization. Fourteen healthy male subjects served as controls [mean age 53.21 years (SEM 1.63)]. Baseline plasma endothelin-1 levels were higher (P < 0.0001) in ischaemic patients [1.81 pg mL-1 (0.15, n = 14)] than in control subjects [0.61 pg mL-1 (0.03, n = 14)], but did not increase with exercise in both groups. Similar results were obtained with dipyridamole infusion. Endothelin-1 levels significantly decreased after coronary revascularization [before: mean 1.81 pg mL-1 (SEM 0.15, n = 14); after: mean 1.16 pg mL-1 (SEM 0.11), P < 0.002], without changes in the peptide response to both tests. In conclusion, elevated plasma endothelin-1 concentrations were found in patients with stable angina compared with non-ischaemic subjects. No changes were observed during exercise or dipyridamole infusion in both groups. Coronary revascularization was followed by a significant decrease in plasma endothelin-1 levels.

Elevated albumin excretion in nonmodulating essential hypertensive patients.

Nonmodulating (NM) essential hypertensives are characterized by abnormal renal and aldosterone responses to angiotensin II. Recently, hyperinsulinemia, hypercholesterolemia, and an increased prevalence of family history of hypertension and myocardial infarction have been shown in NM hypertensives. Since an elevated urinary albumin excretion (UAE) has been indicated as a negative prognostic marker for cardiovascular diseases in essential hypertensives, we evaluated UAE in 50 male patients with mild to moderate essential hypertension (mean age 46.3 +/- 4.4 years), characterized as low renin (LR) (n = 14), modulating (M) (n = 20), and NM patients (n = 16) according to their renin profile and ability to modulate the aldosterone response to a graded infusion of angiotensin II. A group of 14 healthy male subjects (mean age 43.3 +/- 3.9 years) served as control. Resulting data showed that NM had significantly higher UAE (30.7 +/- 10.7 microg/min) than controls (11.9 +/- 2.7 microg/min, p < 0.0001), LR (22.1 +/- 8.4 microg/min, p < 0.05), and M patients (19.7 +/- 6.6 microg/min, p = 0.0001) when all fed a 200-mmol NaCl/day diet. On the contrary, differences in UAE disappeared when all subjects were on a low sodium regimen (10 mmol NaCl/day). Compared to LR and M patients, the NM ones also manifested higher low-density lipoprotein cholesterol levels (p < 0.05). Furthermore, these latter and UAE were positively correlated in NM patients (r = 0.579, p < 0.05) but not in the other subgroups. In conclusion, the current study demonstrates elevated UAE in NM patients, suggesting the NM phenotype is combined to an increased cardiovascular risk.

Elevated plasma endothelin-1 levels as an additional risk factor in non-obese essential hypertensive patients with metabolic abnormalities.

Circulating endothelin-1 concentration was evaluated in 93 lean patients with essential hypertension, of whom 16 had impaired glucose tolerance and hyperlipidaemia, 25 had impaired glucose tolerance, 28 had hyperlipidaemia and 24 had no metabolic abnormalities; we also studied 22 control subjects. All groups were age- and sex-matched. Plasma endothelin-1 levels were higher (p < 0.05) in hypertensive patients with impaired glucose tolerance and hyperlipidaemia than in the remaining groups and were directly correlated with fasting insulin levels (r = 0.506, p = 0.045). Therefore, circulating endothelin-1 concentrations are elevated in hypertensive patients with a high-risk profile due to the presence of metabolic abnormalities, and might favour the development of vascular damage.

Circulating endothelin-1 levels in obese patients with the metabolic syndrome.

We evaluated venous plasma ET-1 concentrations in 18 never-treated obese men (body mass index 31.0 +/- 0.5 kg/m2; age 45.4 +/- 4.3 years) showing the whole features of the above syndrome and 12 control men (age 44.1 +/- 3.6 years). Circulating ET-1 levels were significantly higher in patients than in controls (p < 0.05), and were directly correlated with fasting insulin levels (r = 0.564, p = 0.015) and erythrocyte Na+/Li+ counter-transport activity (r = 0.504, p = 0.033). In conclusion, venous plasma ET-1 levels are elevated in obese men manifesting the whole features of the metabolic syndrome. Due to the biological properties of ET-1, our findings suggest the peptide as a further component of the cluster of cardiovascular risk factors which characterizes this syndrome.

Plasma and urinary digitalis-like substance levels during atrial natriuretic peptide infusion in essential hypertensive patients.

In order to evaluate the effect of atrial natriuretic peptide (ANP) infusion on plasma and urinary digitalis-like substance (DLS) levels, 18 essential hypertensive males (mean age 45.6 +/- 3.8 y) were studied. After 1 week on a normal NaCl intake (120 mmol/24h), patients were randomly double-blindly assigned to receive either ANP (99-126) (0.3 microgram/kg/min) (number of patients = 10) or its vehicle (50 ml isotonic saline) (8 patients) over a period of 60 min, in supine position. Plasma and urinary DLS levels were measured at time -60, 0, 30, 60, 120, 180, and 240 min (infusion time from 0-60 min). During ANP infusion, plasma DLS levels decreased significantly (from 25.2 +/- 6.8 pg/ml at time 0 to 12.5 +/- 5.6 pg/ml at 60 min, p < 0.01), while urinary DLS excretion increased (from 60.5 +/- 26.1 pg/ml at time 0 to 246.3 +/- 34.2 pg/ml at 30 min, p < 0.0001). and 402.3 +/- 44.1 pg/ml at 60 min, p < 0.0001). After 3 h from the end of ANP infusion, both plasma and urinary DLS returned to baseline levels (20.5 +/- 14.4 pg/ml and 84.5 +/- 34.2 pg/ml, respectively). Taken together, our data show that ANP infusion significantly increases urinary DLS excretion, while decreasing its circulating levels. This phenomenon could explain the different response of ANP and DLS to some stimuli, such as acute volume expansion. In fact, the rapid increment of plasma ANP due to an acute increase of extracellular fluid volume might simultaneously inhibit the increase in circulating DLS levels by promoting the urinary excretion of this substance.

Plasma endothelin-1 levels in patients with systemic sclerosis: influence of pulmonary or systemic arterial hypertension.

OBJECTIVES: To investigate the behaviour of circulating endothelin-1 (ET-1) in patients affected by systemic sclerosis and to elucidate the relationship between systemic and pulmonary plasma peptide and arterial pressure levels. METHODS: Plasma ET-1 concentrations were determined in 48 patients affected by systemic sclerosis (41 women, seven men; mean age 47.2 (SD 5.5) years) with or without systemic or pulmonary hypertension (or both). A group of 18 normal volunteers served as controls (15 women, three men; mean age 45.0 (10.1) years). RESULTS: Plasma ET-1 levels were significantly greater in patients affected by systemic sclerosis (1.65 (0.29) pg/ml) than in controls (0.63 (0.19) pg/ml) (p < 0.0001). Pulmonary artery systolic hypertension alone was present in 14 patients with systemic sclerosis (50.5 (8.49) mm Hg, range 37-67 mm Hg), and systemic hypertension alone (160.7 (5.9)/100.6 (3.2) mm Hg) was present in 11 patients. Both conditions were present in 12 patients, while 11 patients had systemic hypertension. There were no significant differences in plasma ET-1 levels between patients with pulmonary hypertension alone (1.62 (0.21) pg/ml) and those with systemic hypertension alone (1.65 (0.43) pg/ml). In particular, patients with normal pulmonary artery and systemic pressures (n = 11) had plasma ET-1 concentrations identical to those found in patients (n = 12) with both pulmonary and systemic hypertension (1.70 (0.15) v 1.64 (0.35) pg/ml, respectively). No correlations were observed between plasma ET-1 and either pulmonary or systemic pressures. CONCLUSION: Systemic sclerosis is characterised by increased plasma ET-1 levels, but neither pulmonary nor systemic hypertension are accompanied by further increase in plasma peptide levels.

Plasma endothelin-1 levels in obese hypertensive and normotensive men.

Plasma endothelin-1 (ET-1) levels were studied in 15 obese hypertensive (mean age 48.5 +/- 3.9 years) and 15 obese normotensive men (mean age 49.5 +/- 3.6 years) before and after weight loss due to an 800 kcal/day diet lasting 12 weeks. Circulating peptide concentrations were also assessed in nonobese hypertensive (n = 11) and normotensive men (n = 12). Baseline plasma ET-1 levels were similar in obese hypertensive (0.87 +/- 0.22 pg/ml) and obese normotensive men (0.91 +/- 0.30 pg/ml). In seven obese hypertensive men, caloric restriction normalized blood pressure levels (systolic: from 166.6 +/- 8.1 to 145.0 +/- 6.3 mmHg, P < 0.0001; diastolic: from 106.6 +/- 5.1 to 89.1 +/- 2.0 mmHg, P < 0.0001) and decreased body mass index (BMI) (from 33.4 +/- 1.6 to 29.6 +/- 2.1 kg/m2, P < 0.002) and plasma ET-1 levels (from 0.93 +/- 0.21 to 0.64 +/- 0.26 pg/ml, P < 0.05). In the remaining obese hypertensive men (n = 8), blood pressure levels were not normalized by caloric restriction despite a significant decrease of BMI and plasma ET-1 levels (from 0.83 +/- 0.23 to 0.60 +/- 0.16 pg/ml, P < 0.04). Weight loss also significantly decreased BMI and ET-1 (from 0.91 +/- 0.30 to 0.65 +/- 0.19 pg/ml, P < 0.01) in obese normotensive men. Baseline ET-1 and fasting insulin levels were significantly correlated in obese hypertensive (r = 0.518, P < 0.05) and obese normotensive men (r = 0.535, P < 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating endothelin-1 levels increase during euglycemic hyperinsulinemic clamp in lean NIDDM men.

OBJECTIVE: To evaluate whether or not insulin stimulates endothelin (ET)-1 secretion in vivo. RESEARCH DESIGN AND METHODS: Plasma ET-1 levels were evaluated in 16 lean normotensive men with non-insulin-dependent diabetes mellitus (NIDDM) (mean age 50.3 +/- 4.1 years) during either a 2-h euglycemic hyperinsulinemic clamp (40 mU insulin.m-2.min-1) or placebo infusion (50 ml isotonic saline) according to a single-blind randomized crossover protocol. RESULTS: Circulating ET-1 levels increased during the euglycemic hyperinsulinemic clamp (from 0.88 +/- 0.38 pg/ml at time 0 to 1.66 +/- 0.22 pg/ml and 1.89 +/- 0.99 pg/ml at 60 and 120 min, respectively [P < 0.05 vs. time 0]) and returned to baseline levels after the discontinuation of insulin infusion (0.71 +/- 0.22 pg/ml after a 30-min period of recovery [NS]). Compared with placebo, the euglycemic hyperinsulinemic clamp induced a significant increase in plasma ET-1 levels at 60 min (P < 0.0001) and 120 min (P < 0.0001). Changes in basal insulin levels and corresponding changes in circulating ET-1 levels after a 2-h euglycemic hyperinsulinemic clamp were significantly correlated (r = 0.771, P < 0.0001). A possible unfavorable effect of ET-1 on the tissue sensitivity to insulin-stimulated glucose uptake was suggested by the presence of a negative correlation between total glucose uptake and baseline ET-1 levels (r = -0.498, P < 0.05). CONCLUSIONS: Our findings indicate that circulating ET-1 levels significantly increase during euglycemic hyperinsulinemic clamp in men with NIDDM. The negative correlation between total glucose uptake and circulating ET-1 levels suggests that the peptide might exert negative effects on the insulin sensitivity of target tissues. The consequent increase in insulin secretion as well as the insulin-related ET-1 release from endothelial cells could favor the development of diabetes-related vascular lesions.

Hormonal and renal responses to atrial natriuretic peptide infusion in low-renin hypertension.

Although atrial natriuretic peptide (ANP) levels are often elevated in low-renin hypertensives, the renal and hormonal effects of ANP infusion have never been evaluated in these patients. To address this topic, 27 lean nondiabetic men affected by uncomplicated essential hypertension were studied. Low-renin patients (n = 9, age 42 +/- 3 years) were defined as those individuals in balance on a low NaCl intake (10 mmol NaCl/day for 1 week) who had a plasma renin activity <0.30 ng angiotensin I/l/s, in both the supine and the upright positions. The remaining hypertensives (n = 18, age 41 +/- 4 years) were classified into the normal-renin group. Six age-matched healthy men (age 40 +/- 2 years) served as controls. After plasma renin activity determinations, both patients and controls were replaced on a normal NaCl intake (120 mmol NaCl/day). After 1 week, either ANP (99-126), at a dose (0.7 pmol/kg/min for 3 h) which is known to induce changes in plasma ANP confined to the range of normality, or its vehicle were infused at 1-week intervals, according to a randomized double-blind crossover design. At time 0, low-renin patients had significantly higher (p < 0.05) levels of plasma ANP (12.4 +/- 2.5 fmol/ml) than normal-renin patients (7.2 +/- 2.4 fmol/ ml) and normotensives (7.4 +/- 3.3 fmol/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal atrial natriuretic peptide and renal responses to saline infusion in nonmodulating essential hypertensive patients.

BACKGROUND: Nonmodulation seems to represent an inheritable trait characterized by abnormal angiotensin-mediated control of aldosterone release and renal blood supply and salt-sensitive hypertension. Recently, we demonstrated that atrial natriuretic peptide (ANP) response to angiotensin II also is altered in nonmodulators. Moreover, an abnormal ANP response to acute volume expansion has been shown by others in hypertensive patients displaying some features of nonmodulators. These data induced us to hypothesize that nonmodulators. These data induced us to hypothesize that nonmodulation could be characterized by an abnormal ANP response to saline load. METHODS AND RESULTS: Forty-three essential hypertensive men were subdivided into low-renin patients (n = 12), nonmodulators (n = 15), and modulators (n = 16) according to their renin profile and ability to modulate aldosterone and p-aminohippurate clearance responses to a graded angiotensin II infusion (1.0 ng.kg-1.min-1 and 3.0 ng.kg-1.min-1 for 30 minutes each) on both a low- (10 mmol Na+ per day) and a high- (210 mmol Na+ per day) Na+ intake. The intravenous saline load (0.25 mL.kg-1.min-1 for 2 hours) performed on a low-Na+ diet increased plasma ANP levels in low-renin (from 14.30 +/- 4.68 to 23.30 +/- 7.52 fmol/mL at 120 minutes, P < .05) and modulating patients (from 10.95 +/- 3.55 to 18.21 +/- 5.42 fmol/mL at 120 minutes, P < .05), whereas it did not change the hormone levels in nonmodulators (from 10.77 +/- 3.25 to 13.83 +/- 5.70 fmol/mL at 120 minutes, P = NS). When patients switched from a low- to a high-NaCl diet, plasma ANP levels increased significantly in all groups. However, when the saline load was repeated on a high-NaCl intake, ANP levels increased in both low-renin and modulating patients (P < .05), whereas it failed to increase in nonmodulators. CONCLUSIONS: Nonmodulating hypertensive patients showed a reduced ANP response to saline infusion in the presence of a normal increase of plasma ANP with dietary NaCl load. The impaired ANP response to saline infusion could be due to a different distribution of volume load and contribute to determining the reduced ability to excrete sodium that is commonly described in nonmodulators.

Effects of atrial natriuretic factor infusion on plasma prorenin levels in hypertensive males.

To evaluate the influence of atrial natriuretic factor (ANF) infusion on circulating prorenin, 20 essential hypertensive males, aged between 40 and 60 years, were studied. After 2 weeks under normal sodium intake (120 mmol NaCl per day), patients were randomly assigned to receive either ANF (0.01 fmol/Kg/min) (n.12 patients) or its vehicle (50 mL of isotonic saline) (n.8 patients) over a period of 60 minutes. Blood samples for plasma renin activity (PRA), prorenin and aldosterone (PAC) were taken at time -60, 0, 20, 40, 60, 120, 180, 240 minutes (infusion time: from 0 to 60 minutes). PRA and PAC decreased during the ANF infusion (PRA: from 0.33 +/- 0.05 ng/L/s at time 0 to 0.10 +/- 0.06 ng/L/s at 60 minutes, p < 0.0001; PAC: from 389.2 +/- 99.8 pmol/L at time 0 to 148.7 +/- 44.3 pmol/L at 60 minutes, p < 0.0001), while returned immediately to baseline levels after the infusion was stopped (PRA: 0.37 +/- 0.11 ng/L/s at 180 minutes, PAC: 251.6 +/- 72.1 pmol/L at time 180 minutes). On the contrary, plasma prorenin increased during ANF infusion (from 1.66 +/- 0.58 ng/L/s at time 0 to 2.44 +/- 0.72 ng/L/s at 60 minutes, p < 0.05), and returned to baseline levels after the end of the infusion (1.86 +/- 0.83 ng/L/s at 180 minutes). These data indicate that ANF infusion may alter only the circulating levels of active renin, without affecting plasma prorenin secretion.

Octreotide, a somatostatin analog, reduces insulin secretion and increases renal Na+ excretion in lean essential hypertensive patients.

The influence of insulin on renal Na+ excretion is still subject to debate. In order to evaluate the effect of insulin suppression on Na+ excretion, 20 never-treated essential hypertensive men and 8 normotensive men were studied. All subjects had a body mass index < 27 kg/m2. Both the glucose and the lipid metabolisms were normal. After 2 weeks under normal NaCl intake (120 mEq NaCl daily), either octreotide, a somatostatin analog, or vehicle were infused in a forearm vein during acute volume expansion (0.30 mL/kg/min isotonic saline given intravenously over a period of 30 min). A double-blind randomized cross-over design was followed, and each subject was given both infusions at a 1 week interval. Blood and urine samples were taken at times--60, 0, 30, 60, 90, 120, 180, 240, and 300 min. Our data showed that octreotide significantly lowered insulin levels in both hypertensives (from 12.2 +/- 2.4 microU/mL at time 0 to undetectable values at time 30 and 60 min) and normotensives (from 11.5 +/- 2.8 microU/mL at time 0, to undetectable values at time 30 and 60 min). Compared to saline infusion alone, octreotide significantly increased Na+ excretion in both hypertensives and normotensives (saline + octreotide v saline alone = P < .05 at time 60 and 90 min). In conclusion, octreotide enhanced the natriuretic response to intravenous Na+ load in both hypertensives and normotensives. The increase in urinary Na+ was accompanied by a significant decrease in plasma insulin levels.

[Sodium-modulating hormones and the pressor response to sodium chloride in essential arterial hypertension]. / Ormoni sodiomodulanti e risposta pressoria al cloruro di sodio nell'ipertensione arteriosa essenziale.

Some predictive markers for NaCl sensitivity, related to the red blood cell membrane or to circulating proteins, have already been described in human essential hypertension. The present study was planned to investigate whether or not some hormones produced by the kidney or acting at the kidney level could be used as new markers for NaCl sensitivity. The study was conducted in 28 not previously treated outpatients affected by uncomplicated mild to moderate essential hypertension. After 15 days on a normal NaCl diet, plasma renin activity (PRA), plasma atrial natriuretic peptide (ANP), and the urinary excretion of active kallikrein were evaluated. The sensitivity of blood pressure to changes in NaCl intake was then assessed in all patients, according to a randomized double blind cross-over design. Each patient was assigned to a high (240 mmol of NaCl/day for 15 days) or low (40 mmol of NaCl/day for 15 days) NaCl intake. During the assessment of NaCl sensitivity, the double blindness was achieved by the use of capsules containing either NaCl or placebo. Fifteen patients (11 males and 4 females) resulted as NaCl-sensitive, while 13 patients (8 males and 5 females) were classified as NaCl-resistant. Our results indicate that PRA levels were significantly lower in the NaCl-sensitive group than in the NaCl-resistant one (0.108 +/- 0.05 ng/L/s vs 0.247 +/- 0.16 ng/L/s, p < 0.007), in the presence of raised levels of plasma ANP in NaCl-sensitive hypertensives (18.08 +/- 4.61 fmol/mL vs 12.45 +/- 3.77 fmol/mL, p < 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal sodium excretory function during acute oxygen administration.

To evaluate the effect of O2 administration and O2 removal on renal Na+ excretion, 12 hypoxemic eucapnic patients affected by chronic obstructive pulmonary disease (COPD) and 9 normal subjects were studied. After 1 h in the supine position, O2 was administered for 3 h by a tight-fitting face-mask. Urine and blood samples for renal Na+ excretion evaluation were taken at times 0, 60 and 180 min. After O2 removal both the blood and the urine samples were taken again for a further 3 h. In normal subjects, urinary Na+ excretion did not vary after both O2 administration and removal. On the contrary, in patients affected by COPD renal Na+ excretion significantly increased during O2 administration (from basal values of 0.08 +/- 0.01 to 0.17 +/- 0.02 mEq/min at 180 min, p < 0.05), and returned to baseline levels (0.13 +/- 0.03 mEq/min) after 3 h from O2 removal. The basal fractional excretion of filtered Na+ was significant lower in hypoxemic patients than in normal subjects (0.72 +/- 0.3% in patients with COPD vs. 0.95 +/- 0.7% in normal subjects, p < 0.05), while, at the end of O2 administration, it became higher in patients with COPD than in controls (1.62 +/- 0.4% in patients with COPD vs. 0.89 +/- 0.5 in control subjects, p < 0.001). In conclusion, our findings showed an oxygen-related increase of both the urinary Na+ excretion and the fractional excretion of filtered sodium in patients affected by COPD.

Effects of short-time insulin suppression on renal sodium excretion in type II diabetic hypertensives.

The effects of a short-time insulin suppression on Na+ excretion were evaluated in 9 type II diabetic hypertensive males. All patients had a body mass index < 26 and normal plasma lipid levels. After 2 weeks under constant NaCl intake (120 mEq of NaCl daily) either octreotide, a somatostatin analogue, or its vehicle were infused in a forearm vein during acute volume expansion (0.20 ml/kg/min isotonic saline given intravenously over a period of 30 min). A double blind randomized cross-over design was followed, and each patient was given both infusions at one week interval. Blood and urine samples for the evaluation of plasma insulin and serum and urine Na+ were taken at time-30, 0, 30, 60, 90, 120, and 240 min. Our data showed that octreotide completely suppressed insulin levels (from time 0 to 60 min). During acute volume expansion+octreotide, Na+ excretion was 0.20 +/- 0.15 mEq/min at time 0, 0.23 +/- 0.21 mEq/min at time 30, 0.64 +/- 0.24 mEq/min at 60 (p < 0.05 vs time 0), 0.71 +/- 0.35 mEq/min at 90 (p < 0.05 vs time 0), 0.78 +/- 0.10 mEq/min at 120 (p < 0.01 vs time 0) and 0.71 +/- 0.12 mEq/min at 240 min (p < 0.05 vs time 0). As compared to acute volume expansion alone, octreotide induced a significant increase of Na+ excretion at 60 and 90 min (p < 0.05). In conclusion, a short-time insulin suppression, as obtained by the somatostatin analogue octreotide, enhances the natriuretic response to intravenous saline load in lean type II diabetic hypertensives.