Radioprotective effect of local administration of lysine-vasopressin and triglycyl-lysine-vasopressin on the rectal mucosa in rats.

Reactions from the rectal mucosa often give rise to troublesome side-effects during and after radiotherapy in the pelvic region. Local vasoconstriction in the rectal mucosa will cause an ischemia which will decrease the sensitivity of the mucosal cells to radiation and thereby these side-effects can be reduced. Triglycyl-lysine-vasopressin applied rectally in 1% Blanose solution gave in the present study significant radioprotection of the rectal mucosa in the doses of 0.8, 1.6, and 3.2 mg. These doses are, however, very high. Triglycyl-lysine-vasopressin in 1.2% Natrosol solution in a dose of 128 micrograms did not show any certain protective effects. However lysine-vasopressin in 1.2% Natrosol solution in a dose of 16 micrograms gave significant radioprotection of the rectal mucosa. This dose level has in a previous study not given any significant effects on the systemic circulation. Lysine-vasopressin in Natrosol solution seems to be a suitable combination for further studies.