EFFECT OF CYSTEAMINE INJECTION OF VASOPRESSIN AND OXYTOCIN BIOSYNTHESIS IN RAT HYPOTHALAMUS

Cysteamine (CSH), a sulfhydryl agent that promotes disulfide-exchange reactions, was studied for its effects on the immunoreactive (IR) leve ls and synthesis of oxytocin and vasopressin in the hypothalamus. CSH injection (300 mg/kg s.c.) caused a rapid (1 h) suppression of S-35-cy steine incorporation into hypothalamic arginine vasopressin (VP) and o xytocin (OT). The reduction in labeling persisted for about 8 h; label incorporation was normal within 10 h of CSH administration. The drug did not influence S-35-cysteine incorporation into acid-precipitable p rotein, nor did it influence S-35-cysteine specific activity in the hy pothalamus. In addition, S-35-VP and S-35-OT molecules could not be re covered from hypothalami of CSH-treated rats by subjecting samples to denaturing, reducing and then reoxidizing conditions. Despite the redu ction in peptide labeling, CSH treatment produced no alterations in th e IR VP and OT contents of hypothalamus or posterior pituitary. These results indicate that CSH causes a true suppression of both VP and OT formation in hypothalamus, and suggest that the effect is either too t ransient to promote a reduction in endogenous stores of either peptide , or that the drug equally inhibits peptide production and removal (i. e., axonal transport, secretion).