Volume of Rabbit and Rat Renal Cortical Slices Permeable to P-Aminohippurate (PAH), Diodrast and Urokon

¹ From the Department of Pharmacology, University of Louisville School of Medicine, Louisville, Kentucky

A method is presented which allows one to measure the permeable volume of the renal cortex to substances which are transported or actively accumulated by the renal cortex. This permeable volume in rat and rabbit renal cortical slices has been measured using PAH, Diodrast and Urokon as the transported substances. It is less than the volume of tissue water. Therefore, a volume of the renal cortex must be impermeable to these substances. It is postulated that all or part of the impermeable volume is made up of the tubular cells. The permeable volumes are 0.474 cc/gm tissue for PAH, 0.542 cc/gm tissue for Diodrast, and 0.447 cc/gm tissue for Urokon, as compared to 0.771 cc/gm for the tissue water. The active accumulation of these substances by rabbit renal cortical slices after 90– 130 minutes is 10.10 µm/gm for PAH, after 90 minutes is 1.90 µm/gm for Diodrast, and after 60–150 minutes is 3.20–3.53 µm/gm for Urokon.