Metabolism of methionine in women using oral contraceptives

• Main Author: Dow, Marjorie J.
• Other Authors: Miller, Lorraine T.
• Language: en_US
• Published: 2011
• Subjects: Oral contraceptives > Side effects
• Online Access: http://hdl.handle.net/1957/26196

The effect of oral contraceptives on the urinary excretion of several methionine metabolites was determined in women before and after they had received a 3-g dose of L-methionine. Nine women between the ages of 20-29 years served as subjects: five had been using a combination-type oral contraceptive for six months or more (experimental group), and four had not been using these drugs (control group). Cystathionine excretion by both groups before and after the methionine loading was in the range reported for normal female subjects who were not deficient in vitamin B₆ (Krishnaswamy, 1972; Shin and Linkswiler, 1974). Changes in urinary methionine metabolites that were apparently produced by oral contraceptive drugs are: (1) homocysteine was detected in the basal urine of three of the oral contraceptive users. After methionine loading, it was found in the urine of four of these subjects, two of whom excreted measurable quantities. In contrast, three of the control subjects excreted traces of homocysteine only after methionine loading. (2) The mean excretion of taurine by oral contraceptive users was only one-tenth of that excreted by the control subjects. The activity of erythrocyte glutamic oxaloacetic transaminase (EGOT) before and after in vitro stimulation with added pyridoxal phosphate was similar in both groups. Basal activity of erythrocyte glutamic pyruvic transaminase (EGPT) was lower in oral contraceptive users, although the mean values for both groups were within the normal range reported by Miller et al. (1975) and Woodring and Storvick (1970). The percent in vitro stimulation after addition of pyridoxal phosphate was somewhat higher in oral contraceptive users, but the difference was not statistically significant. Thirteen free acidic and neutral amino acids (including metabolites of the methionine pathway) were measured in the urine specimens. The sum of the urinary excretion of these 13 amino acids was significantly lower (p < 0.01) for oral contraceptive users than for control subjects. However, total α-amino nitrogen excretion, measured in the same urine specimens, was similar for both groups. === Graduation date: 1976