INACTIVATION OF ARGININE- AND LYSINE-VASOPRESSIN BY SLICES FROM DIFFERENT ZONES OF THE RAT KIDNEY AND BY RAT LIVER SLICES

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Abstract
A method was developed for studying the inactivation of antidiuretic hormone in slices from different zones of the rat kidney. The essential features of the method are The use of thin slices from 4 zones: outer cortex, inner cortex, outer medulla and papilla which are incubated aerobically with the hormone in a medium that has a composition essentially the same as rat extracellular fluid, including a calcium concentration of 2.5 mmol. The inactivation of arginine- and lysine-vasopressin by these slices at 25[degree]C and 37[degree]C for 2 hours was studied. All zones inactivated both vasopressins, but the most marked inactivation activity/mg dry tissue was found in the papillary zone. High concentrations of sodium chloride in the incubation medium did not affect the inactivation of vasopressin by papillary slices. The amounts of arginine- and lysine-vasopressin (expressed in rat pressor units) which were inactivated/mg dry tissue in the different zones during the incubation period were equivalent. Similar results were found in experiments on the inactivation of the 2 hormones by liver slices. These findings are discussed in relation to the problems of the site of action of antidiuretic hormone and the difference in the antidiuretic response to arginine- and lysine-vasopressin which is found after i. v. injection in the rat.