Plasma triglyceride turnover during use of oral contraceptives

Abstract

The effect of oral contraceptives on the concentration, production rate, and removal efficiency of plasma triglycerides was studied in premenopausal women using an endogenous labeling of triglycerides with tritiated glycerol. Thirteen subjects were studied while receiving the drug and seventeen normal healthy females served as controls. In some instances the study was made both before and during the drug or repeated after discontinuation of the treatment. The elimination of triglycerides from the circulation was characterized using the Michaelis constant, K m, which gives the plasma concentration at half-maximal removal velocity. The control group showed a polymorphism of plasma triglyceride kinetics being composed of three subgroups which had different maximal turnover rates. Treatment with oral contraceptives was associated with highly significant increases of concentration, rate of production, and efficiency of removal of plasma triglycerides whereas the maximal turnover rate was apparently unaffected. Thus, the increase of plasma triglyceride concentration (average 1.5-fold) observed in women receiving oral contraceptives is accounted for by a much enhanced influx (average 1.9-fold). The influence of the latter is partly compensated by a simulataneous acceleration of triglyceride efflux, however. The effects are produced already by one cycle of treatment but almost no reversion of the changes can be observed at 1 mo after discontinuation of the drug. The triglyceride concentration and production rate were significantly correlated to the duration of intake of contraceptive preparations while the removal efficiency was not.