Synthesis, Antidiuretic and Pressor Activities of [Arginine4]Arginine-Vasopressin and Two Related Analogues.

Abstract
Using well-established solid-phase techniques, three new analogues of arginine-vasopressin (AVP) were synthesized. In these the glutamine residue in position 4 was replaced with an additional arginine. The new analogues were: [Arginine4]arginine-vasopressin ([Arg4]AVP), [2-thiopropionic acid1,arginine4]arginine-vasopressin (d[Arg4]AVP) and [1-thiocyclohexaneacetic acid1,arginine4]arginine-vasopressin (d(CH2)5[Arg4]AVP). [Arg4]AVP showed about the same antidiuretic activity as AVP but had only about 40% of its pressor activity. Unexpectedly, deamination caused a drop in the antidiuretic activity to about 50%, d(CH2)5[Arg4]AVP had practically negligible antidiuretic and low pressor effects.