Renal Tubular Secretion and Biosynthesis of Organic Acids ∗ †

Abstract

Summary

With the in vitro kidney slice technique, the in vivo steady state and stopflow technique, we have studied the sites and the interrelationship of tubular secretion and biosynthesis of organic acids and found that both occur in the cortex, in the same proximal segment and probably in the same cells. Addition of transported substance, such as PAH or Diodrast, in the medium does not alter the rate of biosynthesis. Simultaneous administration of aminobenzoic acid does not augment, but exhibits either no effect or a slight decrease of tubular transport maximum of the aminohippurate. However, administration of Diodrast would markedly depress the urinary excretion of aminohippurate either by administration or by biosynthesis. Our results indicate that the second step of the transport process, from cell to lumen, is carrier-mediated, and that this carrier can be saturated at a Tm level.