Tritiation of vasopressin analogues and their metabolic fate after intravenous injection in the rat.

Tritiated vasopressin analogues (LVP, AVP, dDAVP) of high specific activity were produced. The labelled peptides were purified by RP-HPLC. The biological half-life, organ distribution and in vivo metabolism of the hormones were studied in the rat. The half-life of dDAVP was longer than that of LVP or AVP. The half-life calculated from [3H]AVP isolated from bloods was shorter than the value based on total radioactivity. The hormones were degraded in the kidney, the liver and small intestine, the main metabolic product being [3H]Tyr. Large radioactivity accumulations were detected in the neurohypophysis and the adenohypophysis.