Proximal tubular cell electrolytes during volume expansion in the rat.

Abstract

1. Proximal tubular intracellular elements were measured by electron microprobe X-ray analysis (a) in rats volume-expanded with albumin-saline in which peritubular oncotic pressure remained normal and (b) in rats in which the renal artery was snared before volume expansion (the early snare model remained unchanged (16-1 + 0 4, 131-0 + 2-0 and 5-2 + 0 3 mmol (kg wet wt)-1, respectively) compared to non-expanded snared kidneys (15-9 + 0-6, 131-3 + 1-8 and 4-8 + 0'3 mmol (kg wet wt)1, respectively).[CF]i at 18-3 + 0 5 mmol (kg wet wt)-' increased (P < 0'0008) compared to controls at 15-8 + 0 5 mmol (kg wet wt)-l. Thus, in these rats, evidence for an inhibition of the Na+ pump was no longer observed. This points to a major intrinsic mechanism within the kidney for mediating natriuresis, since circulating factors were identical to those in the unsnared kidney, where significant natriuresis occurred.

Effect of Atrial Natriuretic Peptide on Cellular Element Concentrations in Rat Proximal Tubules: Evidence for Inhibition of the Sodium Pump

“…This effect of ANP infusion is unlikely to be related to the reduced renal perfusion pressure and must therefore be specific to ANP. Reducing perfusion pressure by an aortic snare in control or volume expanded rats does not cause changes in cell dry weight, [Nali, [K]i or [Rbli (Reddy et al 1994).…”