The role of the pineal in regulating the oncogenic processes was explored in Sprague-Dawley female rats by comparing incidence and growth of mammary
tumors in animals subjected to superior cervical
ganglionectomy (SCGx) or blinding and
anosmia (BAs) with that of intact rats treated with 7-12-dimethylbenz(a)anthracene (DMBA). The surgery was performed at the age of 56 days, 1 day following the administration of the
carcinogen. Growth of mammary
tumors was studied, and 15 weeks later the rats were sacrificed by
decapitation and the activity of the pineal
hydroxyindole-O-methyltransferase (
HIOMT) was determined. Carcinostatic effects of similar magnitude were present in both SCGx and BAs groups as evident from tendency toward reduced
tumor incidence and decreased total
tumor mass. Ganglionectomized rats developed significantly smaller numbers of
tumors than intact control animals. A trend toward reduced
tumor number and increased
tumor regression was evident in the BAs group. Although there was no significant difference in
tumor volumes among the groups, BAs animals showed a distinct trend toward smaller
tumor volumes at the termination of the experiment. Despite similar carcinostatic tendencies, SCGx rats had significantly lower
HIOMT activity than BAs animals. The possible existence of multiple carcinostatic mechanisms in BAs and SCGx rats is discussed.