Inhibition by somatostatin of hepatocarcinogenesis induced by N-nitrosomorpholine in Sprague-Dawley rats.

The effect of somatostatin on hepatocarcinogenesis induced by N-nitrosomorpholine (NNM) was investigated in male Sprague-Dawley rats. Rats were given drinking water containing NNM for 8 weeks and s.c. injections of 200 micrograms/kg body wt of somatostatin every other day from the beginning of the experiment until the end of week 16. Pre-neoplastic and neoplastic lesions staining for gamma-glutamyl transpeptidase (GGT) or placental type glutathione-S-transferase (GST-P) were examined histochemically. Administration of somatostatin for 16 weeks resulted in significant reduction in the percentage volume of GGT-positive and GST-P-positive lesions. The incidence, number and size of hepatocellular carcinomas were significantly less in rats treated with somatostatin than in untreated rats. Administration of somatostatin significantly decreased the labeling indices of pre-neoplastic lesions and adjacent liver. These findings indicate that somatostatin inhibits hepatocarcinogenesis and that this effect may be related to its effect in decreasing cell proliferation in pre-neoplastic lesions.