IN VITRO UPTAKE AND BREAKDOWN OF TRITIATED LYSINE-VASOPRESSIN BY BOVINE NEUROHYPOPHYSEAL AND CORTICAL TISSUE

Abstract

ABSTRACT Pieces of tissue from the neurohypophysis and parietal cortex of cows were incubated in a modified Locke solution containing specifically tritiated lysine-vasopressin (LVP). After incubation, the uptake of radioactivity associated with LVP, 2 peptide split products and tyrosine as well as radioactivity in TCA insoluble proteins was determined. Thin-layer chromatography was used to identify the intact hormone and its split products. The total radioactivity as well as the radioactivity associated with LVP and the aminopeptidase-split products increased much more rapidly in the neurohypophysis than in the cortex. The tissue to medium ratio of radioactivity for LVP and the aminopeptidase-split products quickly became greater than one in the neurohypophysis, whereas it remained below one in the cortex. Radioactivity associated with TCA insoluble proteins quickly appeared. The temperature dependence of the appearance of radioactivity in LVP and the aminopeptidase-split products in both the neurohypophysis and the cortex was complicated, whereas the appearance of radioactivity in tyrosine increased with temperature in a simple manner.