Effects of glycine on serum gonadotropins and estradiol and on concentrations of free amino acids in the middle hypothalamus in female rats.

Abstract

The effects of glycine on serum gonadotropins and estradiol (E2) and on concentrations of free amino acids in the middle hypothalamus have been studied in diestrus-1 rats. 20 min after intraperitoneal administration, glycine in doses of 50 and 100 mg had no significant effect on serum luteinizing hormone (LH) levels, but 200 mg significantly elevated serum LH levels. Glycine in doses of 50-200 mg had no effect on serum follicle-stimulating hormone levels at 20 min after intraperitoneal injection. 200 mg of glycine significantly elevated serum LH levels at 20 and 50 min and serum E2 levels at 50 and 80 min after intraperitoneal injection. The effects were maximal at 20 min after injection for LH and at 50 min after injection for E2. 20 min after intraperitoneal injection, 200 mg of glycine significantly increased the concentration of glycine in the middle hypothalamus, but had no effect on the concentrations of the other free acidic and neutral amino acids in the middle hypothalamus. These results suggest that glycine may play a role in the neural regulation of LH secretion.