In vivo activation of synthetic hormonogens of lysine vasopressin: Na-glycyl-glycyl-glycyl-[8-lysine]vassopressin in the cat.

The urine and plasma levels of vasopressin-like immunological activity and of antidiuretic activity were examined following injection of Na-glycyl-glycyl-glycyl-[8-lysine]vasopressin (triglycylvassopressin, TGLVP) in 3 cats. The plasma levels of immunoreactive material were initially high, and fell rapidly. The levels of antidiuretic activity showed considerable variation; the overall pattern was strikingly different from that demonstrated by radioimmunoassay, and all 3 animals showed a rise in plasma antidiuretic activity in the early part of the experiment. Following injection of lysine vasopressin (LVP) the pattern of disappearance of both biological and immunological activity was similar. The total amount of immunoreactive material found in the urine was greater than the amount of antidiuretically active material. These results clearly demonstrate that the antidiuretic activity of TGLVP is mainly due to its conversion to LVP in vivo.