Influence of replacement of chloride by sulphate upon urine excretion and glomerular filtration rate in blood perfused isolated dog kidneys

Effect of reduced chloride reabsorption on renin release in the isolated rat kidney

To investigate the relationship between tubular reabsorption of chloride and renal renin release in the isolated perfused rat kidney, perfusate renin activity was measured during substitution of either nitrate or thiocyanate for varying amounts of perfusate chloride but with maintained perfusate sodium concentration. Renin rose significantly as perfusate chloride fell; there was a sevenfold increase between perfusion with normal chloride and almost complete substitution of chloride by nitrate. With a normal perfusate chloride the addition of furosemide 10(-4) M to the perfusate also led to an increase in renin and a reduction in tubule chloride reabsorption. For all these experiments there was a significant negative correlation between renin and absolute tubular reabsorption of chloride (r = -0.68, P less than 0.001), but no such relationship with absolute sodium reabsorption. Renin release in a nonfiltering kidney, produced by elevating perfusate albumin concentration, increased approximately 40-fold. Thus increasing plasma oncotic pressure elevates renin by mechanisms additional to cessation of tubular chloride absorption. However, substitution of chloride in the perfusate by nitrate in this nonfiltering kidney did not further elevate renin release. We conclude that renin release is influenced by a signal dependent on, and inversely proportional to, chloride reabsorption in the thick ascending limb of the Loop of Henle.

Regulation of renal blood flow by plasma chloride

Micropuncture studies have shown that glomerular filtration rate (GFR) falls in response to a rise in Na(+) or Cl(-) concentrations in the loop of Henle, whereas studies in isolated kidneys have shown that GFR falls in response to osmotic diuresis. To define the separate effects of an acute increase in plasma sodium (P(Na)), chloride (P(Cl)) or osmolality (P(osmol)), changes in renal blood flow (RBF) and GFR were measured during intrarenal infusions of hypertonic NaCl, NaHCO(3), Na acetate, dextrose, NH(4)Cl or NH(4)acetate to denervated kidneys. The infusions raised P(osmol) at the experimental kidney by 30-45 mosmol. RBF increased abruptly by 10-30% with all hypertonic infusions indicating that an acute increase in plasma tonicity causes renal vasodilatation. Renal vasodilatation persisted or increased further during infusion of dextrose, NaHCO(3) and Na acetate, but GFR was unchanged. In contrast, during infusion of the two Cl-containing solutions, vasodilatation was reversed after 1-5 min and RBF and GFR decreased (P < 0.01) below preinfusion levels. Prior salt depletion doubled the vasoconstriction seen with hypertonic NaCl infusions. Overall, changes in RBF were unrelated to changes in P(Na) or fractional Na or fluid reabsorption but correlated with changes in P(Cl) (r = -0.91) and fractional Cl(-) reabsorption (r = 0.94). The intrafemoral arterial infusion of the two Cl-containing solutions did not increase femoral vascular resistance. In conclusion, hyperchloremia produces a progressive renal vasoconstriction and fall in GFR that is independent of the renal nerves, is potentiated by prior salt depletion and is related to tubular Cl(-) reabsorption. Chloride-induced vasoconstriction appears specific for the renal vessels.

Regulation of renal blood flow by plasma chloride

Micropuncture studies have shown that glomerular filtration rate (GFR) falls in response to a rise in Na(+) or Cl(-) concentrations in the loop of Henle, whereas studies in isolated kidneys have shown that GFR falls in response to osmotic diuresis. To define the separate effects of an acute increase in plasma sodium (P(Na)), chloride (P(Cl)) or osmolality (P(osmol)), changes in renal blood flow (RBF) and GFR were measured during intrarenal infusions of hypertonic NaCl, NaHCO(3), Na acetate, dextrose, NH(4)Cl or NH(4)acetate to denervated kidneys. The infusions raised P(osmol) at the experimental kidney by 30-45 mosmol. RBF increased abruptly by 10-30% with all hypertonic infusions indicating that an acute increase in plasma tonicity causes renal vasodilatation. Renal vasodilatation persisted or increased further during infusion of dextrose, NaHCO(3) and Na acetate, but GFR was unchanged. In contrast, during infusion of the two Cl-containing solutions, vasodilatation was reversed after 1-5 min and RBF and GFR decreased (P < 0.01) below preinfusion levels. Prior salt depletion doubled the vasoconstriction seen with hypertonic NaCl infusions. Overall, changes in RBF were unrelated to changes in P(Na) or fractional Na or fluid reabsorption but correlated with changes in P(Cl) (r = -0.91) and fractional Cl(-) reabsorption (r = 0.94). The intrafemoral arterial infusion of the two Cl-containing solutions did not increase femoral vascular resistance. In conclusion, hyperchloremia produces a progressive renal vasoconstriction and fall in GFR that is independent of the renal nerves, is potentiated by prior salt depletion and is related to tubular Cl(-) reabsorption. Chloride-induced vasoconstriction appears specific for the renal vessels.

Influence of uranyl nitrate upon tubular reabsorption and glomerular filtration in blood perfused isolated dog kidneys

The early changes in tubular reabsorption, glomerular filtration, blood flow and sodium excretion brought about by uranyl nitrate were investigated in isolated, blood-perfused dog kidneys during water diuresis. No significant changes in urine volume were observed; the decrease in fluid reabsorption was counterbalanced quantitatively by a reduction in glomerular filtration rate; only a small diminution of renal blood flow was found. The balance between reabsorption and filtration was observed as well when angiotensin action or prostaglandin synthesis were inhibited. The intrarenal venous pressure rose, suggesting that an increase in proximal intratubular hydrostatic pressure caused the decrease in filtration. Tubular back-leak of fluid, or back-diffusion, induced by the toxin, were excluded. The presence of natriuretic compounds in the urine was confirmed.

Connection between the changes in tubular reabsorption and in glomerular filtration rate induced by replacement of plasma sodium and chloride by isotonic mannitol

Glomerular filtration and tubular reabsorption have been investigated comparatively in isolated blood-perfused dog kidneys, after addition to the blood of equal volumes of isotonic sodium chloride or isotonic mannitol. In the absence of antidiuretic hormone activity, the urine output showed no significant difference, while the glomerular filtration rate was lower in the presence of the mannitol load. The inhibition of fluid reabsorption was compensated by the decrease of filtration; a quantitative tubulo-glomerular equilibrium was evidenced. The fractional sodium excretion was decreased following the dilution by the mannitol load of plasma sodium and -chloride; this difference disappeared when the reabsorption in the diluting segment was inhibited by furosemide, suggesting that it depended on the rate of chloride reabsorption in this part of the tubule.