Intrarenal pressure and sodium excretion in hypertension of chronic glomerulonephritis in humans

Renal hemodynamics in rats with cadmium-induced nephropathy

Glomerular filtration rate (GFR) is known to decline in patients with cadmium (Cd)-induced nephropathy. However renal hemodynamics in Cd-induced nephropathy remain unknown. We investigated renal hemodynamics in experimental Cd-induced nephropathy. Male Sprague-Dawley rats were given 0.18 mg/rat of cadmium chloride i.p. three times a week for 3 and 16 months. Age-matched control rats were given physiological saline. Mean arterial pressures after 3 and 16 months were identical among the groups. In comparison with age-matched control rats, significant decreases in GFR associated with a significantly lower filtration fraction (FF) were demonstrated in both groups of Cd-treated rats, but the changes were more prominent in the 16-month Cd-treated rats. Renal plasma flow was significantly decreased in the 3-month Cd-treated rats whereas it was preserved in the 16-month Cd-treated rats because of anemia. Urinary sodium excretions in both groups of Cd-treated rats were significantly greater than those in the respective control rats. On light microscopic examination, only mild degeneration of tubular cells and interstitial edema in limited areas of the proximal tubules were observed in the 3-month Cd-treated rats. In the 16-month Cd-treated rats multifocal tubular atrophy and interstitial fibrosis in the outer cortex were noted. Electron microscopic examinations revealed conspicuous degenerative changes in the proximal tubular epithelial cells, diffuse thickening of glomerular basement membranes, and foot process fusions in 16-month Cd-treated rats. These data suggested that the decline in GFR in the Cd-treated rats resulted mainly from the decline in FF, which might be functional rather than structural in origin and might be associated with proximal tubular dysfunctions.

Renal effects of manidipine hydrochloride. A new calcium antagonist in hypertensive patients

The renal effects of manidipine hydrochloride were investigated in ten hospitalised patients with mild-to-moderate essential hypertension. After a one-week placebo period, manidipine was given for 1 week in a dose rising from 5 mg to 10 mg or 20 mg daily to normalise the mean blood pressure measured after 2 h. Blood pressure had decreased from 171/101 to 147/86 mm Hg at the end of manidipine treatment. The pulse rate was unaltered. Renal vascular resistance decreased from 1.90 to 1.33 dyn.s.cm-5/1.48 m2 x 10(4), and renal blood flow and glomerular filtration rate increased from 522 to 662 ml.min-1 x 1.48 m-2 and from 81 to 93 ml.min-1 x 1.48 m-2, respectively, in spite of a fall in renal perfusion pressure. Manidipine reduced the filtration fraction from 0.260 to 0.243, suggesting a preferential reduction in efferent arteriolar resistance. The fractional excretion of sodium and potassium did not change. Manidipine did not produce any significant alteration in plasma renin activity or in the plasma aldosterone concentration. The results indicate that manidipine has favourable renal effects and a concomitant hypotensive action in patients with mild-to-moderate essential hypertension.

Renal effects of nicardipine, a calcium antagonist, in hypertensive type 2 (non-insulin-dependent) diabetic patients with and without nephropathy

The renal effects of oral maintenance doses of nicardipine 60-120 mg/day have been studied in 18 hypertensive patients with Type 2 (non-insulin-dependent) diabetes mellitus: 6 with normoalbuminuria (urinary albumin excretion rate, AER less than 20 micrograms.min-1, Group A); 6 with incipient nephropathy, (AER 20-200 micrograms.min-1, Group B); and 6 with overt nephropathy (AER greater than 200 micrograms.min-1, Group C). Treatment for 4 weeks significantly lowered the systolic and diastolic blood pressures and reduced total renal vascular resistance in all three groups. Nicardipine increased renal blood flow significantly in Group C and slightly in Group B, and had no effect in Group A. Glomerular filtration rate remained unchanged in all three groups. It significantly reduced AER and the fractional clearance of albumin in Group B, whereas AER in Groups A and C was not altered. Plasma renin activity, aldosterone concentration, osmotic pressure, serum total protein and albumin concentrations and haemoglobin A1c level were similar in the control and nicardipine phases in all three groups. The results suggest that nicardipine may preserve renal function whilst having a concomitant hypotensive action in hypertensive Type 2 diabetic patients with normoalbuminuria and incipient nephropathy, and that the drug may improve renal blood flow in patients with overt nephropathy. The effect of the drug on urinary albumin excretion may deserve further investigation.

Effects of dilevalol, an R, R-isomer of labetalol, on blood pressure and renal function in patients with mild-to-moderate essential hypertension

The effects of oral dilevalol (an R, R-isomer of labetalol), a new beta-adrenoceptor blocker with beta 2-receptor stimulating and alpha-recepter blocking properties on blood pressure, renal function, plasma renin activity (PRA) and plasma aldosterone have been studied in 15 patients with mild-to-moderate essential hypertension treated with it for 6 weeks. Two patients with apparent treatment failure and one patient who developed muscle pain and cramps, and had an elevated creatine phosphokinase level, were excluded from the study. Dilevalol monotherapy 100 mg once daily for 6 weeks significantly lowered both the systolic and diastolic blood pressure compared to placebo. Total renal vascular resistance was significantly reduced, and RBF and GFR remained unchanged. Dilevalol significantly decreased PRA. The results suggest that prolonged daily treatment with dilevalol preserves renal function and produces a concomitant hypotensive action in patients with mild-to-moderate essential hypertension. The ancillary pharmacological properties of dilevalol rather than PRA suppression may be relevant to its renal effects.

Renal effects of nicardipine in patients with mild-to-moderate essential hypertension

We studied the renal effects of nicardipine, a calcium entry blocker, in seven patients with mild-to-moderate essential hypertension. Glomerular filtration rate (GFR) and renal blood flow (RBF) were measured by means of thiosulfate and para-aminohippurate, respectively. Intravenous administration of nicardipine hydrochloride (0.5 mg) increased RBF by 26.8 +/- 5.8% (mean +/- SEM, p less than 0.01), GFR by 35.4 +/- 12.4% (p less than 0.05), and urinary excretion of sodium by 56.4 +/- 10.7% (p less than 0.05) with a significant (p less than 0.01) reduction in systolic and diastolic blood pressure as compared to control values. Nicardipine decreased total renal vascular resistance by 30.0 +/- 3.2% (p less than 0.05) from the control value, while filtration fraction remained unchanged. Our results indicate that nicardipine has several favorable renal effects with a concomitant hypotensive action in patients with mild-to-moderate essential hypertension.

Arginine vasopressin and cyclic adenosine monophosphate during acute sodium loading in chronic glomerulonephritis

The relationship of arginine vasopressin (AVP) in plasma to cyclic adenosine 3' 5'-monophosphate (cAMP), sodium excretion in urine, and arterial blood pressure were determined during intravenous infusion of hypertonic sodium chloride solution (500 ml of 50 g/l) in 10 normotensive control subjects and in 11 normotensive and 10 hypertensive patients with chronic glomerulonephritis and relatively well preserved kidney function. The concentration of AVP in plasma increased 2-4 fold, osmolality in serum increased 12-16 mosmol/kg, and urinary excretion of cAMP increased 20-40% during sodium loading to the same extent in all three groups. Sodium and water excretion were higher during the sodium loading in the hypertensive patients, but not in the normotensive patients when compared to the control subjects. Neither AVP nor changes in AVP correlated significantly with changes in cAMP excretion, sodium excretion or blood pressure. In the control subjects the level of parathyroid hormone in serum was unchanged during the sodium chloride infusion. Water loading without sodium loading in eight of the control subjects caused a decrease in the excretion of cAMP. In conclusion, the increase in cAMP excretion in urine during the sodium loading might be explained by an AVP-induced stimulation of renal cAMP production. The study does not suggest that AVP plays a role in the increased sodium excretion during sodium loading or in the development of hypertension or chronic glomerulonephritis.

Renin-angiotensin-aldosterone system in exaggerated natriuresis of chronic glomerulonephritis

Angiotensin II (AII) and aldosterone (Aldo) in plasma, blood pressure (BP) and urinary excretion of sodium were studied before, during and in two periods after intravenous sodium loading with 500 ml of sodium chloride solution (50 g/l) in 11 normotensive and 10 hypertensive patients with histologically verified chronic glomerulonephritis and creatinine clearance in the range from 11 to 167 ml/min, and in 10 normotensive control subjects. The absolute increase of sodium excretion during loading was higher in the patients grouped together and in the hypertensives alone, but not in the normotensive patients when compared with the control subjects. No correlation was found between sodium excretion and control mean BP or change in mean BP during loading. AII and Aldo were suppressed during loading in both patients and control subjects. In the patients but not in the control subjects the increase of sodium excretion correlated positively with pre-infusion value of AII and negatively with change in AII during the sodium loading. No correlation was found between sodium excretion and Aldo and changes of Aldo. In conclusion, the results might suggest that the renin-angiotensin system is involved in the regulation of exaggerated natriuresis in chronic glomerulonephritis.