The hormone potentiating capability of amino acids on lactational performance in rats injected with 7,12-dimethylbenzanthracene (DMBA) during gestation.
DMBA administered to pregnant rats caused a significant decrease in mammary gland RNA and DNA contents on day 1 of lactation. Some amino acids had gonadotropic-like and/or estrogenic-like activity. In order to determine the effects of reproductive amino acids on DMBA primed mammary gland tissue, female adult virgin Long Evans rats (12 animals/group) were intraperitoneally injected daily with 1 mg DMBA in 0.2 ml sesame oil on days 8 through 12 of pregnancy. On days 8 through 17 of gestation these rats were subcutaneously injected with 150 mg/kg body weight of either L-tryptophan, L-arginine, or L-glycine in 1 ml saline solution. On day 1 of lactation L-tryptophan and L-glycine significantly increased the depressed DMBA control values for total RNA (mg), RNA (mg/100 g B.W.), RNA (mg/100 mg M.G.), RNA/DNA and the DNA (mg/100 g B.W.) to that of sesame oil controls. However, L-arginine had no stimulatory effect on the RNA or DNA values. The data suggests that L-glycine, which increases growth hormone release, and L-tryptophan, which enhances and mimicks prolactin secretion, negate the harmful effects of DMBA by stimulating mammary gland growth (i.e., DNA) and secretion (i.e., RNA).