APStracts 2:0132F, 1995.

Compartmentation of amino acids in the rat kidney. Silbernagl, Stefan, Katharina V[diaeresis]olker, and William H. Dantzler. Physiologisches Institut, Universit[umlaut]at W[umlaut]urzburg, D -97070 W[umlaut]urzburg, Germany, and Department of Physiology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA

APStracts 2:0132F, 1995.

Amino acid concentrations, [AA], were determined in cortical, outer and inner medullary (OM, IM) and in papillary tissue of rat kidney (Ctissue; mmol/kg wet weight) and in plasma (Cpl) and urine. In all regions, Tau, Gly and Glu- had the highest Ctissue making up 54 to 65% of the total [AA]: Cortex 27, OM 21, IM and papilla 11 mmol/kg W.W. Cortical cell water [AA], Ccwat, (mmol/kg H2O) were between 12.4 (Tau) and 0.09 (Orn+) representing plasma water to cell water ratios (Cpwat/Ccwat) between 134 (Asp-) and 0.9 (Thr, Cit). Short-term water diuresis did not change the total tissue [AA] throughout the kidney. Treatment of the tissue with triton X-100 instead of sulfosalicylic acid (SSA) resulted in much higher [AA] except for Glu-, GluNH2, Tau and exogenous L-homoarginine+ (hoArg+). When hoArg+ was infused (leading to a Cpl = 5.9 mmol/l), Ctissue of hoArg+ was similar throughout the kidney (13 to 22 mmol/kg w.w.). In presence of hoArg+, Ccwat/Cpwat of Arg+ rose 13-fold. We conclude that (1) AA con tribute 20% to cytosolic osmolality in renal cortex; (2) Total [AA] decreases from cortex to papilla; (3) cellular uptake of Tau and anionic AA must be rheogenic, whereas cationic AA (except for Arg+ in cortex) are passively distributed; and (4) AA do not seem to contribute quantitatively to short-term medullary osmotic adaptation during diuresis.

Received 3 April 1995; accepted in final form 21 July 1995.
APS Manuscript Number F111-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.