Effect of Anti-Diuretic Hormone and Calcium on the Equivalent Pore Radius of Kidney Slices from Necturus

Abstract

THE passive permeability of kidney slices may be expressed in terms of the equivalent pore radius. The present work is concerned with measurement of this parameter for kidney slices from the amphibian, Necturus maculosus, both under normal conditions, and as affected by the action of anti-diuretic hormone and calcium. Measurements have been made by the method of D. A. Goldstein and A. K. Solomon (private communication), which depends on the determination of the external concentration of permeant solute required to prevent water movement into or out of the cell at the instant of immersion in the medium. When the initial rate of change in volume of the cell is zero, the cell is in transient osmotic equilibrium with its environment. As Staverman¹ has pointed out, the concentrations required to produce transient osmotic equilibrium are higher for permeant solutes than for impermeant ones. Goldstein and Solomon have shown how these zero -time isotonic concentrations may be related to the equivalent pore radius.