Acute cardiovascular effect of 1,25-dihydroxycholecalciferol in essential hypertension

A role for vitamin D in the pathophysiology of essential hypertension has frequently been suggested, but acute direct effects on blood pressure, cardiac output, renal hemodynamics, or hormones have not previously been demonstrated. The rapid effects of 1,25-dihydroxycholecalciferol (1,25-D) were assessed over 120 min after a bolus injection (0.02 microg/kg body weight) in eight men with essential hypertension and in nine healthy men. A placebo group of 10 healthy men was also included. Ionized calcium was monitored closely during the study, and was kept constant with a clamping technique. In the hypertensive patients, a transient increase in blood pressure and a reciprocal fall in cardiac output measured by a CO2 rebreathing technique (-15%, P < .05) were observed after 1,25-D injection. In the control group, both blood pressure and cardiac output remained unchanged. The glomerular filtration rate, effective renal plasma flow, and urinary sodium and water excretions were unchanged in both groups. Plasma levels of atrial natriuretic peptide at baseline were higher in the hypertensive patients than in the control subjects (P < .02); plasma levels of renin, aldosterone, norepinephrine, endothelin, and parathyroid hormone(1-84) were similar in the two groups. None of these hormones was affected during the observation time after the injection of 1,25-D. In conclusion, acute administration of 1,25-D caused a fast and likely nongenomic-mediated decrease in cardiac output in patients with essential hypertension, which together with a transient BP increase implies a 1,25-D-induced increase in total peripheral resistance. These data suggest an enhanced cardiovascular responsiveness to 1,25-D in hypertensive compared to healthy normotensive subjects.

Effects of PTH(1-34) on blood pressure, renal function, and hormones in essential hypertension: the altered pattern of reactivity may counteract raised blood pressure

As it has been suggested that parathyroid hormone (PTH) is implicated in the pathophysiology of essential hypertension, the effects of PTH(1-34) were assessed during infusion over 120 min in ten men with essential hypertension and in ten healthy men. Ionized calcium was kept constant by a clamping technique. Mean arterial blood pressure fell slightly in the patients (116 mm Hg, median, before, and 108 mm Hg during the infusion, P < .01), but remained unchanged in the controls (median 87 mm Hg). The pulse rate rose to a similar extent in the two groups, but cardiac output, measured by the CO2 rebreathing technique, was unchanged. The glomerular filtration rate (GFR) was slightly lower in the hypertensives than in the controls at baseline (92 v 109 mL/min, P < .02), but it increased similarly during PTH infusion in both groups (+13% v +9%, medians), as did the effective renal plasma flow (+50% v +38%). The urinary rate of sodium excretion, which was similar at baseline, increased more in the patients than in the controls (+191% v +46%, P < .05); this was mainly attributable to a reduction in the tubular reabsorption of sodium. Calculations based on lithium clearance indicated that mainly the proximal tubular reabsorption of sodium decreased during PTH infusion. Baseline plasma PTH(1-84) was higher in the patients than in the controls (20.5 ng/L v 16.5 ng/L, P < .05). The baseline plasma values of renin, aldosterone, atrial natriuretic peptide, endothelin, and noradrenaline were similar in the two groups. During infusion of PTH, renin increased less in the patients than in the controls (P < .02), and aldosterone increased only in the controls (P < .01). The other hormonal values remained unchanged. In conclusion, the patients with essential hypertension had increased baseline PTH values, but nevertheless PTH had more marked vasodilative and natriuretic effects than in the controls. PTH thus seems to counteract rather than aggravate elevation of blood pressure in these patients.

Regulation of renal sodium and water excretion in the nephrotic syndrome and cirrhosis of the liver

Atrial natriuretic peptide (ANP) produced in the heart and prostaglandin E2 (PGE2) synthesised in the kidneys facilitate renal excretion of sodium and water, and thus oppose the actions of angiotensin II, aldosterone, arginine vasopressin (AVP), endothelin, and the renal sympathetic nerves. In the present work we studied the contributions and interactions of these substances in the regulation of blood volume (BV), renal haemodynamics, renal sodium and water handling and blood pressure (BP) in patients with glomerulonephritis and cirrhosis. The aim was through a better understanding of the pathophysiology to improve the treatment of fluid retention in these patients, which occurs as development of the nephrotic syndrome and accumulation of ascites, respectively. Normotensive patients with glomerulonephritis but without the nephrotic syndrome had normal baseline BV values measured as the sum of plasma volume and red cell volume; they responded to BV expansion after infusion of albumin and BV depletion after administration of furosemide with appropriate counterregulatory hormonal changes. However, they tended to hold more fluid within the intravascular phase after both manipulations than did the healthy subjects. The acutely induced increase in BV did not affect the BP, which was likely attributable to the changes in plasma values of angiotensin II and ANP shown. ANP could be expected to be a tool in the management of fluid accumulation in patients with the nephrotic syndrome and cirrhosis. The non-renal effects of high-dose ANP were studied for the first time in dialysis patients without excretory kidney function. A reversible shift of fluid away from the intravascular phase was demonstrated. The BV was maximally reduced 30 min after ANP had been given. The BP was reduced before fluid displacement occurred and to the same extent in patients and healthy subjects. The reduction in the BV was negatively correlated to the reduction in BP. From that study it is inferred that the BP reducing effect of ANP is not mediated by its diuretic effect or ability to displace fluid from the intravascular to the interstitial fluid compartment. As a pharmacological dose of ANP was given, it can only be suggested that endogenous ANP, by altering transcapillary Starling mechanisms, assists in buffering intravascular fluid expansion until renal excretion or dialysis can take place. The same dose of ANP was given to patients with the nephrotic syndrome and cirrhosis. The ability of ANP to increase sodium excretion through inhibition of sodium reabsorption in the distal tubules and to increase the glomerular filtration rate (GFR) was blunted in both patient groups, but the BP was reduced to the same extent as in the healthy controls. Patients with the nephrotic syndrome tended to have a slightly elevated BP. We only studied patients with normal or slightly reduced GFR. They had a normal BV, reduced renal filtration fraction, suppressed aldosterone, increased ANP, but normal plasma values of angiotensin II, endothelin, and AVP, and normal urinary excretion of PGE2. Thus, neither haemodynamic nor hormonal factors can easily explain the spontaneous sodium retention or the resistance to the effects of ANP and furosemide. An interesting finding, not previously reported in nephrotic humans, was the low cyclic guanosine 3'5'-monophosphate (cGMP) in plasma and urine in relation to ANP, both before and after administration of ANP. It is hypothesised that renal resistance to ANP, exaggerated renal cGMP degradation, or preponderance of clearance receptors in nephrotic kidneys may contribute to sodium retention and the low filtration fraction. Elevation of ANP in these patients is connected with increased albuminuria, and probably an increase in intraglomerular capillary pressure. The resistance to furosemide could not be attributed to delayed passage of fluid from the interstitial to the intravascular fluid phase, but is most likely due to renal tubular resistan

Hypertension and left ventricular hypertrophy in patients with spontaneous subarachnoid hemorrhage

One hundred eighteen consecutive cases of spontaneous subarachnoid hemorrhage seen at one hospital during a 3-year period were examined to assess the prevalence of hypertension and the correlation between the presence of hypertension and the risk of early death. Eighty-seven of the patients had intracerebral aneurysms. The diagnosis of hypertension was determined by means of three complementary criteria: a history of treatment with antihypertensive drugs; systolic and/or diastolic blood pressure levels > or = 160 and 95 mm Hg, respectively, measured by the general practitioners of the patients before the onset of the subarachnoid hemorrhage; and the presence of left ventricular hypertrophy determined by echocardiography and/or necropsy. The major findings were as follows: 1) hypertension was present in at least 41% of the patients; 2) in 37% of 51 patients with no history of hypertension before the hemorrhage, left ventricular hypertrophy was diagnosed; and 3) the frequency of hypertension and left ventricular hypertrophy was significantly higher in patients who died within 14 days after the bleeding episode compared with patients surviving this period.

Effects of high dose atrial natriuretic peptide on renal haemodynamics, sodium handling and hormones in cirrhotic patients with and without ascites

To elucidate and to try to reverse the antinatriuretic mechanisms in liver cirrhosis, atrial natriuretic peptide (ANP) was given as a pharmacological bolus dose (2 micrograms per kg body weight) to 14 cirrhotic patients, and as a control to 14 healthy subjects. The nine patients with ascites had baseline values of glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and blood pressure (BP) similar to controls. Their distal tubular fractional reabsorption of sodium (DFRNa), estimated by the lithium clearance technique, was higher than in controls, and so were plasma values of aldosterone (564 vs. 119 pmol l-1 medians), endothelin (1.23 vs. 0.63 pmol l-1), ANP (7.5 vs. 3.6 pmol l-1) and cyclic GMP (8.8 vs. 4.6 nmol l-1); p < 0.01 for all. The five patients without ascites had higher GFR and ERPF, and lower plasma angiotensin II than controls. After ANP injection, similar plasma levels of ANP and cyclic GMP were reached in all groups. Urinary sodium excretion rate increased in controls (0.23 to 0.52 mmol min-1, p < 0.01), while GFR increased (108 to 117 ml min-1, p < 0.05), and DFRNa decreased (93 to 89%, p < 0.01). In cirrhotics with ascites sodium excretion was unaltered (0.12 to 0.11 mmol min-1), and so was GFR (84 to 83 ml min-1). Proximal tubular fractional reabsorption of sodium increased after 90 min, whereas DFRNa decreased immediately (97 to 96%, p < 0.01) though less markedly than in controls. Sodium excretion increased in four of five patients without ascites (0.23 to 0.27 mmol min-1, medians). In patients with ascites, endothelin in plasma decreased after ANP (p < 0.05). Plasma levels of angiotensin II, aldosterone and vasopressin were unchanged in all groups. In conclusion, although hyper-reabsorption of sodium occurred in the distal rather than the proximal part of the nephron in cirrhotic patients with ascites, ANP had no natriuretic effect. This was most probably due primarily to the lack of increase of GFR and blunted inhibition of DFRNa, attributed to high aldosterone. The effect of ANP in suppressing the high endothelin did not seem to improve sodium excretion.

Reduced natriuretic effect of atrial natriuretic peptide in nephrotic syndrome: a possible role of decreased cyclic guanosine monophosphate

To evaluate therapeutic and side effects, atrial natriuretic peptide (ANP) was administered as a pharmacological bolus dose (2 micrograms/kg body weight) to 7 patients with nephrotic syndrome and to 13 age- and gender-matched control subjects. The basal glomerular filtration rate was similar, but the blood pressure was slightly higher in the patients than in the controls. Injection of ANP induced a significant increase of sodium excretion in controls (from 0.21 to 0.52 mmol/min, medians, p < 0.01), but not in nephrotics (from 0.21 to 0.32 mmol/min). Urinary output and free water clearance after ANP had been given were also lower in the patients. The natriuretic effect was mediated through inhibition of distal tubular fractional sodium reabsorption, as estimated by the lithium clearance technique, and through an increase of glomerular filtration rate, both effects only significant in the healthy subjects. The blood pressure was reduced to the same extent in the two groups. Although similar levels of ANP were reached in the groups after injection, cyclic guanosine monophosphate (GMP)/ANP was less in the patients, both basally and after ANP injection, and the urinary excretion of cyclic GMP did not increase in the nephrotics (from 478 to 1,220 pmol/min, ns) as in the controls (from 389 to 2,500 pmol/min, p < 0.01). The urinary albumin excretion rate increased significantly in patients, whereas the prostaglandin E2 excretion increased after ANP administration only in controls. Endothelin, angiotensin II, aldosterone, and arginine vasopressin were unchanged in the two groups. Basal aldosterone was lower and ANP higher in patients than in controls. In conclusion, the natriuretic effect of ANP was reduced in nephrotic patients. This could not be attributed to counterregulatory haemodynamic or hormonal factors, but probably to reduced second messenger cyclic GMP.

Parathyroid hormone in blood pressure and volume homeostasis in healthy subjects, hyperparathyroidism, liver cirrhosis and glomerulonephritis. A possible interaction with angiotensin II and atrial natriuretic peptide

In order to elucidate a participation of intact parathyroid hormone (PTH(1-84)) in blood pressure (BP) and body fluid homeostasis, we studied fluctuations of PTH(1-84) during manipulations of BP in hyperparathyroid and healthy subjects, and during manipulations of blood volume in patients with glomerulonephritis or liver cirrhosis and in controls. Angiotensin II induced BP elevation was associated with increased values of PTH(1-84) both in healthy subjects (12-25 ng l-1, medians, p < 0.01), in patients with primary hyperparathyroidism (94-125 ng l-1, p < 0.01), in patients with low calcium due to end stage renal disease before requirement of dialysis (95-151 ng l-1, p < 0.02), and in patients with tertiary hyperparathyroidism (221-264 ng l-1, p < 0.05), but not in dialysis patients without hypercalcaemia (126-174 ng l-1, NS). The changes could not be attributed to reduction of serum calcium, but probably to the increase of plasma angiotensin II, which was positively correlated to the increase of serum PTH(1-84) in the healthy subjects (p = 0.619, n = 15, p < 0.05) and in the patients with primary hyperparathyroidism (p = 0.549, n = 18, p < 0.05). Noradrenaline induced BP elevation did not have a similar effect on PTH(1-84), and changes of PTH(1-84) were not related to changes of BP. Volume depletion after furosemide injection, also accompanied by increased levels of angiotensin II, resulted in elevation of PTH(1-84) in controls, cirrhotics, patients with glomerulonephritis without the nephrotic syndrome, but not in nephrotic patients. Volume depletion induced by bolus injection of atrial natriuretic peptide (ANP) was associated with decreased PTH(1-84) in healthy subjects (20-18 ng l-1, p < 0.02), but not in patients with nephrotic syndrome and liver cirrhosis. Volume expansion induced by albumin infusion caused increased plasma levels of ANP, but PTH(1-84) was unaltered. Thus, angiotensin II may be able to stimulate, and ANP to inhibit release of PTH(1-84), and PTH(1-84) may be involved in the regulation of BP and body fluid homeostasis. BP changes or changes in blood volume per se do not seem to influence PTH(1-84) levels.

Unchanged noradrenaline reactivity and blood pressure after corrective surgery in primary hyperparathyroidism

In order to evaluate the role of the hyperparathyroid state for blood pressure and volume homeostasis, eight patients with primary hyperparathyroidism were studied before and after corrective surgery. Neither noradrenaline induced blood pressure changes nor basal blood pressure were affected by the operation, and the values were the same as in an age- and sex-matched control group. Noradrenaline infusion induced an increase in PTH(1-84) values before (72-86 ng l-1, medians, p < 0.02), in contrast to a decrease after (28 to 19 ng l-1, p < 0.05) operation for primary hyperparathyroidism. Basal plasma atrial natriuretic peptide was lower before than after removal of adenomata (3.2 vs. 4.8 pmol l-1, medians, p < 0.02). Cyclic 3'-5'-guanosine monophosphate was not significantly changed (4.7 vs. 5.5 nmol l-1). Aldosterone was higher before than after surgery (139 vs. 71 pmol l-1, p < 0.02), whereas angiotensin II was unaltered (20 vs. 9 pmol l-1). Arginine vasopressin was higher before than after the operation (0.9 vs. 0.7 pmol l-1, p < 0.05), but urinary excretion of prostaglandin E2 was unchanged. In conclusion primary hyperparathyroidism was not associated with changes in noradrenaline reactivity or basal blood pressure despite derangements of hormones adjusting sodium and water homeostasis. It is suggested that the hormonal changes may be secondary to a relative volume depletion.

Atrial natriuretic peptide and parathyroid hormone (1-84) in relation to noradrenaline induced changes in blood pressure in uraemic and healthy subjects

In order to evaluate the hormonal regulation of blood pressure (BP) in uraemia 12 patients on chronic maintenance dialysis and 14 healthy controls were studied. BP and plasma concentrations of atrial natriuretic peptide (ANP), cyclic 3',5'-guanosine monophosphate (cGMP), and intact parathyroid hormone (PTH(1-84)) were determined before, during, and after a 60 min noradrenaline infusion 0.1 micrograms kg-1 body wt. min-1. Mean BP increased to the same extent in the uraemic patients (median 15 mmHg, range 6-25 mmHg) as in the controls (12 mmHg, 5-25 mmHg). ANP increased during noradrenaline infusion both in patients (7.2 to 8.3 pmol/l, medians, p < 0.01) and in controls (4.4 to 6.0 pmol/l, p < 0.01), and so did cGMP (patients: 31.6 to 35.9 nmol/l, p < 0.05; controls: 6.6 to 8.7 nmol/l, p < 0.01). PTH(1-84) was higher in the uraemic patients than in the controls, but was unchanged during noradrenaline infusion in both groups. Correlation analyses gave no evidence of a direct relation between BP and ANP, but basal PTH(1-84) was negatively correlated to basal mean BP in the patients (rho = -0.615, p < 0.05), but not in the controls. In conclusion, noradrenaline induced similar elevations of BP in dialysis patients as in healthy controls despite elevated ANP and PTH(1-84) in the patients, and ANP release was stimulated in both groups. PTH(1-84) may participate in blood pressure regulation in uraemic patients.

Renal and hormonal effects and tolerance of an ANP analogue in healthy man

The effect of an analogue of atrial natriuretic peptide (P-ANP) on glomerular filtration rate (GFR), renal plasma flow (RPF), urinary flow rate, urinary sodium excretion, tubular function estimated by the lithium clearance technique, and plasma levels of sodium and water homeostatic hormones, has been studied in 40 healthy males. Placebo or P-ANP 0.3, 1.5, or 3.0 micrograms.kg-1 bwt were given as an intravenous bolus injection to different groups. P-ANP did not cause any immediate change in GFR or RPF, but significant dose-dependent increases in filtration fraction, urinary flow rate and urinary excretion rate of sodium were detected during the first 30 min after administration. Proximal absolute and fractional tubular reabsorption and distal absolute tubular reabsorption of sodium did not change after injection of P-ANP, while the distal fractional reabsorption of sodium was reduced in a dose dependent manner during the first 30 min. Plasma angiotensin II and aldosterone were significantly increased 30 and 150 min after dosage, whereas plasma atrial natriuretic peptide, plasma arginine vasopressin, and urinary excretion of prostaglandin E2 were unchanged. Cyclic guanosine monophosphate both in plasma and urine were increased in a dose-dependent manner. P-ANP cause a significant reduction in diastolic blood pressure and an increase in pulse rate. Two subjects had vasovagal syncope 30-60 min after injection of P-ANP. It is concluded that P-ANP has natriuretic, diuretic and hypotensive properties in healthy man.

Attenuated renal excretory response to atrial natriuretic peptide in congestive heart failure in man

The renal and hormonal effects of atrial natriuretic peptide given as a bolus injection (2.0 micrograms/kg) were studied in 12 patients with congestive heart failure before and after treatment with captopril for 4 weeks and in 13 healthy control subjects. Atrial natriuretic peptide caused a rise in urinary excretion of sodium and urinary flow in the controls, whereas no increases were observed in the patients. Both proximal and distal fractional reabsorption of sodium, as evaluated by the lithium clearance technique, decreased less in the patients than in the controls. Basal plasma concentrations of atrial natriuretic peptide and cyclic guanosine monophosphate (cGMP), and the basal urinary excretion of cGMP, were elevated in the patients. The increases in both plasma and urinary cGMP after administration of atrial natriuretic peptide were blunted in heart failure. Basal glomerular filtration rate and renal plasma flow were reduced, and filtration fraction increased, in the patients. A positive correlation (r = 0.958, P less than 0.01) was found between renal plasma flow and the relative increase in urinary excretion of sodium in the patients with heart failure. Treatment with captopril did not improve the natriuretic and diuretic effect of exogenous atrial natriuretic peptide, but resulted in an increase in filtration fraction after administration of atrial natriuretic peptide not present before captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal tubular handling of sodium and water induced by atrial natriuretic peptide in essential hypertension

Atrial natriuretic peptide (ANP) was given as an intravenous bolus injection (2.0 micrograms kg-1) to 12 essential hypertensive patients (EH) and 13 normotensive control subjects (C) in order to study the effect of ANP on renal glomerular and tubular function using the lithium clearance technique. Urinary sodium excretion (EH, + 370% vs. C, + 120%; P less than 0.001) and urine volume (EH, + 137% vs. C, + 62%; P less than 0.01) increased significantly more in EH than in controls after ANP injection. Glomerular filtration rate, renal plasma flow, and plasma concentrations of angiotensin II, aldosterone and arginine vasopressin remained almost unchanged after ANP injection, whereas the filtration fraction increased to the same extent in both groups. Both proximal (EH, - 15% vs. C, - 5%; P less than 0.01) and distal fractional reabsorption (EH, - 12% vs. C, - 5%; P less than 0.01) of sodium decreased more markedly after ANP in EH than in controls. The increase in plasma cGMP and urinary excretion of cGMP was the same in the two groups. Mean blood pressure decreased and heart rate increased to the same extent in both groups. It is concluded that the increase in urinary sodium excretion and urine volume induced by ANP bolus injection is exaggerated in EH due to a more pronounced reduction in the reabsorption of sodium and water in both the proximal and the distal tubule.

Mechanisms of sodium retention in heart failure: relation to the renin-angiotensin-aldosterone system

Renal plasma flow (RPF), glomerular filtration rate (GFR), renal proximal tubular delivery of sodium and water evaluated by lithium clearance, and hormonal parameters were measured in 12 patients with congestive heart failure NYHA class II-IV before and after captopril treatment for 4 wk and in 13 healthy control subjects. RPF and GFR were significantly decreased in heart failure, whereas the filtration fraction (FF) was increased. Treatment with captopril increased RPF and decreased FF, whereas GFR was unchanged. Total and fractional urinary excretion of sodium were reduced in the patients compared with the controls, but increased after captopril. Fractional excretion of lithium was normal in heart failure and was increased by captopril. Atrial natriuretic peptide, guanosine 3',5'-cyclic monophosphate, and aldosterone in plasma were significantly elevated in heart failure and were reduced by treatment with captopril. Plasma renin activity was increased in patients, correlated inversely with RPF, and increased further after captopril treatment. It is concluded that the reduced sodium excretion in heart failure was caused by a combination of diminished glomerular filtration and enhanced tubular reabsorption beyond the proximal tubule and that treatment with captopril increased urinary sodium excretion partly due to an attenuated sodium reabsorption in the proximal tubule. The present data in patients with congestive heart failure are consistent with an increased intrarenal angiotensin II generation and an elevated plasma level of aldosterone being involved in the pathogenesis of the glomerular hemodynamic changes and the enhanced distal tubular reabsorption, respectively.

Effect of frusemide on atrial natriuretic peptide, guanosine cyclic monophosphate, angiotensin II, aldosterone, vasopressin, prostaglandin E2 and blood volume in the nephrotic syndrome

Blood volume, plasma concentrations of atrial natriuretic peptide, guanosine cyclic monophosphate (cGMP), angiotensin II, aldosterone and arginine vasopressin, and urinary excretion rate of prostaglandin E2, cGMP, sodium, and water were determined before and after intravenous administration of frusemide 0.75 mg/kg body-weight in nine patients with the nephrotic syndrome and 15 control subjects. The decrease in blood volume and the increase in urinary sodium and water excretion after fusemide were significantly reduced in the nephrotic patients compared with the controls. Atrial natriuretic peptide was reduced after frusemide both in patients (6.2 to 4.9 pmol/l, medians, P less than 0.05) and controls (5.9 to 4.8 pmol/l, P less than 0.01), but the nadir was delayed in the patients, and cGMP in plasma and urine was reduced only in the controls. The angiotensin II increase was delayed in the patients and aldosterone increased only in the controls. Basal urinary excretion of prostaglandin E2 was less in the nephrotic patients than in the controls (P less than 0.05), but after frusemide the prostaglandin E2 excretion rate increased in the patients (0.25 to 0.62 pmol/min, P less than 0.05), but not in the controls (0.46 to 0.39 pmol/min). In conclusion, reduced water and sodium excretion after frusemide in the nephrotic syndrome is accompanied by a diminished reduction of blood volume, a delayed decrease in atrial natriuretic peptide, and a blunted increase in angiotensin II and aldosterone compared with healthy subjects. Sodium excretion after frusemide may be more dependent on PGE2 production in nephrotic patients than in healthy subjects.

Abnormal glomerular and tubular response to intravenous frusemide in patients with chronic glomerulonephritis

Fourteen normotensive patients with chronic glomerulonephritis and well-preserved renal function and thirteen healthy control subjects were studied. Glomerular filtration rate (GFR), proximal and distal absolute and fractional tubular reabsorption (PAR, PFR, DARNa, DFRNa), evaluated by the lithium clearance technique, were determined before and in four 30-60-min periods after intravenous injection of frusemide 0.5 mg/kg body weight (Study 1) and 1.0 mg/kg body weight (Study 2). Plasma concentrations of angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP) and arginine vasopressine (AVP) were measured before, and 60 and 180 min after frusemide. GFR decreased and UNa and FENa increased significantly in patients and controls after frusemide in both studies, but in study 2 GFR decreased significantly more in patients than in controls, and UNa and FENa increased significantly less above baseline in patients compared to controls. PAR, PFR, DARNa, and DFRNa were reduced in patients and controls in both studies. In study 2 the reduction in PAR was significantly (P less than 0.05) less pronounced in patients (23%) than in controls (43%), whereas DARNa was reduced significantly more (P less than 0.05) in patients (36%) than in controls (21%). The efficiency of frusemide with regard to renal sodium excretion was significantly reduced in patients compared to controls in both studies. Angiotensin II and aldosterone increased, ANP decreased, and AVP was unchanged in patients and controls in both studies. It is concluded that in comparison to control subjects, patients with chronic glomerulonephritis and well-preserved GFR respond to frusemide with an exaggerated reduction in GFR, a lesser decrease in absolute proximal tubular reabsorption, and a larger reduction in absolute distal tubular reabsorption. Thus, primary glomerular disease with well-preserved glomerular function may be accompanied by a distinctly disturbed tubular function.

Comparison of calcium carbonate and aluminium hydroxide as phosphate binders on biochemical bone markers, PTH(1-84), and bone mineral content in dialysis patients

Bone mineral content, estimated by single-photon absorptiometry of the forearm, serum values of intact parathyroid hormone (PTH(1-84], osteocalcin, alkaline phosphatase, 1,25-dihydroxycholecalciferol (1,25(OH)2D3), and aluminium were determined during treatment with calcium carbonate (CaCO3) or aluminium hydroxide (Al(OH)3) in 11 dialysis patients participating in a randomised cross-over study. Each treatment period lasted 6 months. Serum phosphorus was maintained in the range 1.5-2.0 mmol/l. During Al(OH)3 treatment bone mineral content (BMC) decreased by 11% per half-year (mean), but only by 3% per half-year during CaCO3 treatment (P less than 0.05). Comparing the CaCO3 and Al(OH)3 periods the following differences were found: serum calcium increased during CaCO3 treatment, PTH(1-84) decreased (79% of initial values during CaCO3 versus 196% during Al(OH)3, mean area under curve, P less than 0.05), osteocalcin decreased (89% versus 117%, P less than 0.01), alkaline phosphatase decreased (92% versus 116%, P less than 0.05), and aluminium decreased (56% versus 189%, P less than 0.05). 1,25(OH)2D3 remained unchanged in both periods. No increase in soft-tissue calcification was demonstrated on X-ray of the shoulders in any of the periods. Thus, CaCO3 treatment seems to slow down loss of bone mineral content, and using CaCO3 as phosphate binder may have a more beneficial effect on the progression of uraemic bone disease than Al(OH)3 due to the reduction of hyperparathyroidism and bone turnover.

Atrial natriuretic factor, cyclic 3',5'-guanosine monophosphate and prostaglandin E2 in liver cirrhosis: relation to blood volume and changes in blood volume after furosemide

Plasma concentrations of atrial natriuretic factor (ANF) and cyclic 3',5'-guanosine monophosphate (cGMP) were measured in 11 cirrhotic patients with ascites, 11 cirrhotic patients without ascites and 15 control subjects. The following were determined in 15 of the cirrhotic patients and in all the control subjects: blood volume (BV) and furosemide-induced changes in BV, plasma values of ANF, cGMP, angiotensin II (AII), aldosterone (Aldo), arginine vasopressin (AVP) and urinary excretion rates of cGMP, prostaglandin E2 (PGE2), water and sodium. Basal plasma levels of ANF and cGMP were higher in patients with cirrhosis than in controls, but were the same in both groups of cirrhotics (ANF: cirrhosis with ascites 12.7, without ascites 13.4, and in controls 5.8 pmol l-1 (medians); cGMP: 7.7, 7.4 and 4.3 nmol l-1, respectively). BV was less reduced after furosemide in the cirrhotic patients (6.0%) than in the healthy subjects (10.1%), but basal BV did not differ. Urinary sodium excretion rates after furosemide were significantly lower in the cirrhotic patients than in the controls. PGE2 excretion rate increased after furosemide in the cirrhotic patients (0.29 to 0.66 pmol min-1; P less than 0.01) but not in the controls (0.31 to 0.38 pmol min-1). After furosemide ANF and cGMP decreased slightly in both groups whereas AII and Aldo increased; AVP increased in the controls, but not in the cirrhotic patients. In conclusion, plasma values of ANF and cGMP are increased in liver cirrhosis both with and without ascites. This and the elevated PGE2 excretion after furosemide may be compensatory phenomena in order to facilitate renal sodium excretion.

Atrial natriuretic factor, angiotensin II, aldosterone, arginine vasopressin and urinary prostaglandin E2 excretion in hyperfiltrating unilaterally nephrectomized humans

To investigate the degree to which long-term adaptive changes in the remaining kidney after unilateral nephrectomy are dependent on hormonal factors, we measured resting plasma levels of atrial natriuretic factor (ANF), angiotensin II (Ang II), aldosterone (Aldo), arginine vasopressin (AVP), urinary excretion of prostaglandin E2 (UPGE2), creatinine clearance, and fractional sodium excretion (FENa) in 11 unilaterally nephrectomized persons (UNP) 1-11 years after operation and in 13 control subjects (study 1). Additionally, to investigate whether the remnant kidney's ability to excrete an acute sodium load is dependent on hormonal changes, Ang II, Aldo, AVP, sodium excretion, UPGE2, and free-water reabsorption (TcH2O) were measured in response to acute intravenous sodium loading in nine UNP and 14 controls (study 2). Study 1 showed that UNP exhibited hyperfiltration compared with controls (creatinine clearance 79 ml/min/1.73 m2/kidney vs 53, p less than 0.01) and increased FENa (0.82% vs 0.58, p less than 0.01). Despite this, ANF, Ang II, Aldo, and AVP did not deviate significantly from controls. UPGE2 was increased in UNP compared with controls (108 ng/24 h/kidney vs 64, p less than 0.01). Study 2 showed that UNP exhibited a normal natriuretic response but an exaggerated increase in TcH2O (6.0 ml/min/kidney vs 3.9, p less than 0.02). However, the response in plasma levels of Ang II, Aldo and AVP was the same in UNP and in controls. We conclude that the long-term adaptation in the remaining kidney after unilateral nephrectomy does not involve any major changes in ANF, Ang II, Aldo, or AVP. The increase in PGE2 may be a compensatory phenomenon that tends to preserve renal function.

Atrial natriuretic peptide and blood volume in patients with chronic glomerulonephritis: effects of albumin and frusemide administration

Blood volume, blood pressure, plasma concentrations of atrial natriuretic peptide (ANP), cyclic 3',5'-guanosine monophosphate (cGMP), angiotensin II, aldosterone, and arginine vasopressin (AVP), and urinary excretion rates of cGMP, sodium, and water were determined before and after infusion of human albumin 20%, 3.5 ml/kg body-weight to 12 patients with chronic glomerulonephritis and 19 healthy control subjects (Study 1); and before and after frusemide injection, 0.75 mg/kg to 15 patients with chronic glomerulonephritis and 19 healthy control subjects (Study 2). In Study 1 blood volume was expanded to the same degree in patients (8.8 and 7.5%, medians, after 90 and 180 min) and controls (8.6 and 6.1%). ANP was enhanced in the patients (5.9 to 11.0 pmol/l, P less than 0.01) and the controls (4.9 to 7.1 pmol/l, P less than 0.01), but the elevated level was protracted in the patients simultaneously with a delayed sodium excretion. Plasma cGMP increased, aldosterone decreased and AVP was unchanged in both groups, whereas angiotensin II decreased in the patients (P less than 0.01), but not in the controls. In Study 2 blood volume was reduced to a smaller extent in the patients than in the controls (8.9% versus 9.9%, P less than 0.05). ANP an cGMP decreased, and angiotensin II, aldosterone and AVP increased in both patients and controls. In conclusion, patients with glomerulonephritis respond to albumin- and frusemide induced changes in blood volume with essentially the same counter-regulatory changes in ANP, angiotensin II, aldosterone and AVP as do healthy subjects. The more protracted increase in ANP and the decrease in angiotensin II after albumin, and the smaller blood volume reduction after frusemide suggest an abnormal regulation of blood volume in glomerulonephritis.

Effect of atrial natriuretic peptide on blood pressure, guanosine 3':5'-cyclic monophosphate release and blood volume in uraemic patients

1. Eleven patients on chronic maintenance dialysis were investigated before and after intravenous bolus injection of atrial natriuretic peptide (2 micrograms/kg body weight). 2. Mean blood pressure was reduced to the same extent in the uraemic patients as in 11 healthy subjects, with a nadir 3 min after the atrial natriuretic peptide injection at which time mean blood pressure was reduced by 13% (median) in the uraemic patients and 11% in the healthy subjects. 3. Basal plasma atrial natriuretic peptide and guanosine 3':5'-cyclic monophosphate levels were higher in the uraemic patients than in the healthy subjects, but guanosine 3':5'-cyclic monophosphate increased markedly in both groups after atrial natriuretic peptide injection. 4. Using changes in gamma-emission from blood after previous labelling of erythrocytes with 51Cr, and changes in packed cell volume, haemoglobin and erythrocyte count, a reversible shift of fluid from the intravascular phase was demonstrated in the uraemic subjects. The blood volume was maximally reduced by 6% (median) of initial blood volume at 30 min after atrial natriuretic peptide injection. 5. Correlation analyses gave no evidence of a causal relationship between the changes in mean blood pressure and changes in blood volume, angiotensin II, aldosterone or arginine vasopressin after atrial natriuretic peptide injection. 6. It is concluded that a pharmacological dose of atrial natriuretic peptide reduces blood pressure in uraemic patients on maintenance dialysis to the same extent as in healthy subjects. The blood-pressure-reducing effect of atrial natriuretic peptide does not seem to be mediated by its diuretic effect or ability to displace fluid from plasma to the interstitial fluid compartment.

Differentiation between renovascular and essential hypertension by means of changes in single kidney 99mTc-DTPA clearance induced by angiotensin-converting enzyme inhibition

Blood pressure (BP), plasma renin concentration (PRC), and 99mTc-labeled diethylenetriaminepenta acetate (DTPA) renography with determination of single kidney 99mTc-DTPA clearance and parenchymal mean transit time (MTT) were measured in exactly the same way on two consecutive days in 14 patients with renovascular hypertension (RVH), unilateral renal artery stenosis in nine and bilateral stenosis in five, and ten patients with essential hypertension (EH). The examination on day 1 served as a control for day 2 during which captopril (25 mg) was given orally one hour before measurements of PRC and DTPA clearance. Blood pressure was reduced by captopril in both groups, but the maximum decrease in systolic BP was slightly more pronounced (P less than .01) in RVH (22%, median) than EH (13%). Plasma renin concentration increased to a much greater extent (P less than .01) after captopril in RVH (366%) than in EH (46%), Single kidney 99mTc-DTPA clearance was significantly (P less than .01) reduced (-39.5%) and MTT considerably prolonged (170%) on the affected/most affected side in RVH, but both parameters were only slightly changed or unchanged on the unaffected/least affected side (-6.5%, -2% respectively) and were not significantly changed in any of the sides in EH. The degree of renal artery stenosis was significantly correlated to the increase in PRC (rho = -0.786, n = 14 patients, P less than .01), to the reduction in single kidney 99mTc-DTPA clearance (rho = 0.729, n = 19 kidneys, P less than .01) and to the prolongation in MTT (rho = -0.785, n = 16 kidneys, P less than .01). By analysis of the captopril-induced changes in 99mTc-DTPA clearance and MTT, it was possible to predict the existence of a moderate to several renal artery stenosis in arterial hypertension with a very high degree of probability, and the use of changes in 99mTc-DTPA clearance and MTT after angiotensin-converting enzyme (ACE) inhibition may become a valuable tool in differentiation between RVH and EH.

Abnormal structure and function of isolated subcutaneous resistance vessels from essential hypertensive patients despite antihypertensive treatment

The morphological and functional characteristics of isolated subcutaneous resistance vessels (about 230 microns internal diameter) from 13 patients treated for essential hypertension for a median period of 14 months and from 15 matched normotensive controls were examined. The blood pressure of the patients and the controls were not significantly different at the time of examination. However, although compared with the controls, the lumen diameter of the vessels from the patients was not significantly different, the media thickness to lumen diameter ratio was 19% greater. Furthermore, although there was no difference in the active pressure response of the vessels from the two groups, the vessels from the patients had a lower sensitivity to calcium, relaxed faster after a contraction and the sensitivity to exogenous noradrenaline shifted more to the left with cocaine. Since the abnormalities found here have previously also been found in vessels from patients with untreated essential hypertension, the study suggests that despite antihypertensive treatment to normotensive levels for about 1 year, some morphological as well as functional characteristics of the resistance arteries are not fully normalized. This could have consequences for the prognosis of essential hypertension.