Inhibitory effect of sialoadenectomy on hepatocellular tumourigenesis in male mice induced by 3'-methyl-4-dimethylaminoazobenzene.

Male C57BL/6xDS-F1 mice that had been treated with 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) neonatally were subjected to sialoadenectomy (removal of the submandibular salivary glands) 60 days after birth. The development of adenomatous nodules and carcinomas in the livers of these mice was compared with the livers of males without sialoadenectomy. The incidence of adenomatous nodules in sialoadenectomized males at 6, 8, 10, and 12 months was significantly lower than that in sham-operated animals. Carcinomas were found in the livers of both sham-operated and sialoadenectomized males that were 10 and 12 months old and were less frequent in sialoadenectomized males although the difference was significant only at the age of 12 months. Sialoadenectomy decreased the serum concentration of epidermal growth factor (EGF) by about 40%. The present results indicate that sialoadenectomy inhibits the development of hepatocellular tumours induced by 3'-Me-DAB in male mice, an effect which may be caused by decrease in the serum level of EGF.