RAT MAMMARY-CARCINOMA REGRESSIONS DURING SUPPRESSION OF SERUM GROWTH-HORMONE AND PROLACTIN

Abstract

Female rats bearing N-nitrosomethylurea-induced mammary carcinomas were treated with pergolide mesylate to suppress serum prolactin. The drug was given alone, or with somatostatin, 20 .mu.g/h delivered by osmotic minipump for 7 days to suppress serum growth hormone. Tumor regressions did not occur with pergolide alone, but did so promptly in all of 5 rats when growth hormone levels were also suppressed by somatostatin. A potent long-acting agonistic analog of somatostatin, L362823, produced similar tumor regressions at a dose of 5 .mu.g/h when given with pergolide, but was ineffective alone. This dose completely prevented the episodic release of pituitary growth hormone.