Recent research on some aspects of proximal tubular transport phenomena

Abstract

Important themes in the study of the metabolism of the kidney have included the relationship between ion transport and energy production, acid-base bal­ ance and the control of renal ammonia production, and regional differences in metabolic pathways within the kidney. The relationship between ion transport and en­ ergy production was investigated in the past pri­ marily by determining the effect on renal oxygen consumption of varying net renal sodium reabsorp­ tion in vivo, usually in the dog. While such studies provided some information on the metabolic cost of sodium transport, quantitative interpretation of these experiments using the intact kidney is difficult [1]. More recently techniques have been developed which permit investigation of the relationship be­ tween ion transport and metabolism in different parts of the nephron. The purpose of this chapter is to describe how such recent technical advances are providing a better understanding of the relationship between ion transport and energy production in the mammalian proximal tubule. Studies of the metabolism of the proximal tubule will be emphasized because recent advances in ex­ perimental methodology have allowed the develop­ ment of a quantitative description of the relationship between active ion transport and oxidative metabo­ lism in this nephron segment. Such recent advances include development of a proximal tubular suspen­ sion with improved function [2] and utilization of inhibitors in the isolated, perfused tubule technique. 2. Active cation transport: the 'pacemaker' of respi­ ration