Evidence for a Precursor in Vasopressin Biosynthesis

Abstract

Infusion of ³⁵S-cysteine into the third ventricle of dogs for a period of 1.5 hr did not yield significant quantities of labeled vasopressin. However, animals sacrificed 4.5 hr after 1.5 hr of isotope infusion yielded ³⁵S-vasopressin. If puromycin was administered from the start of the experiment, then labeling of vasopressin was not observed. Puromycin, administered after the isotope had been infused, did not prevent the subsequent appearance of labeled hormone either in vivo or with hypothalamic-median eminence (HME) slices incubated in vitro. The HME slices, in the presence of puromycin, gave rise to ³⁵S- or 3H-vasopressin only if the in vitro incubation was preceded by the infusion of ³⁵S-cysteine or 3H-tyrosine, respectively, into the third ventricle of a dog for 1.5 hr prior to sacrifice. It is suggested that the biosynthesis of vasopressin occurs via the intermediate formation of a precursor molecule which contains the hormone in a bound biologically inactive form. (Endocrinology75: 943, 1964)