Effect of oral contraceptives and vitamin B6 supplements on alanine and glycine metabolism.

Plasma alanine or glycine concentrations and blood pyruvate were studied before and after oral administration of the two amino acids to women using estrogen-containing oral contraceptives and to a control group of women. Thirty oral contraceptive users and 14 controls received alanine loads (200 mg/kg of body weight). The two groups had similar fasting plasma alanine levels, but the fasting blood pyruvate was elevated in the contraceptive steroid-treated women. After alanine ingestion, the increases in plasma alanine were significantly lower in the oral contraceptive users. Both groups showed a rise in blood pyruvate; there were no differences in the increments above fasting values. Treatment with pyridoxine hydrochloride, 25 mg for 4 weeks, had not effect on the responses of 11 oral contraceptive users to alanine loading. Twenty-four oral contraceptive users and 14 controls were studied before and after a glycine load (140 mg/kg of body weight). The fasting plasma glycine levels were similar, but lesser increases after ingestion of the amino acid occurred in the oral contraceptive-treated group. Blood pyruvate concentrations in both oral contraceptive users and controls were unaffected by oral glycine loads.