Urinary excretion of prostaglandin F2 alpha and 6-keto-prostaglandin F1 alpha during volume expansion in patients with glomerulonephritis

Evidence of prostacyclin deficiency in the syndrome of hyporeninemic hypoaldosteronism

Hyporeninemic hypoaldosteronism is an important cause of hyperkalemia and is characterized by low renin secretion. We found that prostacyclin, a potent vasodilator and renin secretagogue, was markedly reduced--as reflected by its stable urinary metabolite 6-keto-prostaglandin F1 alpha--in seven patients with hyporeninemic hypoaldosteronism as compared with seven matched controls with renal insufficiency and as compared with 12 normal volunteers (mean +/- SE, 42 +/- 7 vs. 185 +/- 37 and 164 +/- 20 ng per gram of creatinine, respectively; P less than 0.001). In contrast, renal prostaglandin E2 excretion was similar in all three groups. A low-dose infusion of calcium or norepinephrine (known stimulants of prostacyclin) increased renal prostacyclin release in normal subjects and controls with renal insufficiency. Neither agonist, however, increased the low basal prostacyclin excretion in the patients (49.6 +/- 11 [basal] vs. 62 +/- 20 [norepinephrine] and 47.5 +/- 16 [calcium]; P greater than 0.8). To evaluate the functional importance of the altered prostacyclin production, we studied the responses of renal blood flow and blood pressure to the calcium infusion. The calcium infusion did not alter blood pressure or renal blood flow in the normal subjects or the controls with renal insufficiency. In contrast, the same dose of calcium in the patients with hyporeninemic hypoaldosteronism produced a rise in mean blood pressure (from 91 +/- 6 to 104 +/- 8 mm Hg, P less than 0.05) and a fall in renal blood flow (from 673 +/- 58 to 560 +/- 42 ml per minute per 1.73 m2, P less than 0.05). These results indicate that a deficiency of prostacyclin could explain the low active-renin concentration and altered vasomotor tone seen in hyporeninemic hypoaldosteronism.

Arginine vasopressin excretion in response to volume expansion in the healthy human, and in patients with glomerulonephritis

The urinary excretion of arginine vasopressin (AVP) was studied during volume expansion (VE) in nine healthy normotensive individuals and 14 patients with active IgA glomerulonephritis (GN). The studies were started after 17-18 h of food and fluid deprivation (hydropenia, HP) and VE was induced by a continuous infusion of Ringer solution up to an amount corresponding to 3% of the body weight. The clearance of inulin and PAH, urine osmolality and urinary excretion of sodium and AVP were determined. The AVP excretion decreased in response to VE in the healthy individuals, both when related to GFR (from 129 +/- 17 pg min-1 100 ml-1 GFR during HP to 65 +/- 9 after 3% VE, P less than 0.01) and to body surface area (BSA) (from 134 +/- 22 pg min-1 1.73 m-2 BSA to 75 +/- 11, P less than 0.05). In the patients with IgA GN, who had normal blood pressure and normal GFR, the AVP excretion tended to decrease, but the change was not significant (0.05 less than P less than 0.1). The patients with hypertension but essentially normal GFR, and those with hypertension and markedly decreased GFR did not change their renal excretion of AVP in response to VE. If related to the GFR, the latter patients had a markedly increased AVP excretion.