Metabolic side-effects of oral contraceptives

Plasma homocysteine in women on oral oestrogen-containing contraceptives and in men with oestrogen-treated prostatic carcinoma

The mechanism by which oral oestrogen-containing contraceptives in women and oestrogen treatment of prostatic carcinoma in men increases the risk of vascular disease is unclear. These agents decrease serum concentrations of vitamin B12, pyridoxal 5-phosphate, and folate, all of which are essential for the metabolism of the atherogenic amino acid homocysteine. We found serum vitamin B12 concentrations to be lower in 17 women using oral contraceptives (219 +/- 84 pmol l-1) than in 13 age-matched female controls (385 +/- 129, p less than 0.001), but similar values were obtained in the two groups both for fasting plasma homocysteine concentrations (9.1 +/- 2.4 vs 9.2 +/- 3.6 mumol l-1) and for the increase in these concentrations after methionine loading (19.2 +/- 7.5 vs 17.8 +/- 5.2 mumol l-1). In five men with prostatic carcinoma, high-dose oestrogen treatment decreased serum vitamin B12 concentrations by a mean of 30% (p less than 0.05) within 4 weeks, during which fasting plasma homocysteine concentrations decreased (13.8 +/- 4.5 vs 10.5 +/- 2.8 mumol l-1) and response to methionine loading increased (12.4 +/- 3.4 vs 17.3 +/- 5.1 mumol l-1), though the latter changes were non-significant. Our findings do not support the hypothesis that hyperhomocysteinemia explains cardiovascular risk in women using oral oestrogen-containing contraceptives, or in oestrogen-treated men with prostatic carcinoma.

Combined toxic effects of tetracycline and ethinyl estradiol on liver function of mice

The combined effects of ethinyl estradiol (EE) (0.5 micrograms/g s.c. once daily for 4 days) and tetracycline (TC) or doxycycline (DC) (50 micrograms/g i.v.) on liver weight and water content, serum transaminases, alkaline phosphatase, urea, triglycerides, and cholesterol as parameters of various liver functions were investigated in mice. It became apparent that depending on the parameter tested synergistic and antagonistic effects may occur, e.g., synergistic effects were observed with the serum transaminases and liver cholesterol; antagonistic effects were seen with the serum urea and serum cholesterol.

Plasma and erythrocyte membrane fatty acids in oral contraceptive users

The fatty acid composition of the plasma choline phosphoglycerides (CPG) and erythrocyte phospholipids were determined in women using oral contraceptive agents and age-matched female controls. Those using oestrogen and progestogen combined preparations had higher concentrations of palmitic acid (16:0) and linoleic acid (18:2 omega 6) and lower concentrations of stearic acid (18:0) and long chain polyunsaturated fatty acids (LCP), in particular arachidonic acid (20:4 omega 6) and eicosapentaenoic acid (20:5 omega 3), in their plasma CPG than controls. These differences were reflected in the erythrocyte phospholipids. The progestogen-only group had similar concentrations to matched controls. It is suggested that the lower concentrations of LCP in combined pill users may affect membrane function and prostaglandin synthesis and may relate to their increased risk of thrombosis.

Plasma lipoprotein induction and suppression of the generation of cellular procoagulant activity in vitro: two procoagulant activities are produced by peripheral blood mononuclear cells

In the process of analyzing the effects of lipoproteins on functions of lymphoid cells, it was observed that physiological concentrations of isolated human plasma lipoproteins possess varying capacities to rapidly enhance the expression of procoagulant activity of human peripheral blood mononuclear cells in vitro. In a strict dose-dependent fashion, very low density lipoprotein, intermediate density lipoprotein, and high density lipoprotein enhanced both the surface expression by viable cells and the total cellular content of procoagulant activity during a 6-h incubation. Very low density lipoprotein induced a maximal 6.7-fold increase in the expression of a thromboplastin activity, which was consistent with tissue factor, in that it was dependent on Factors VII, X, and II. Both intermediate density lipoprotein and high density lipoprotein induced approximately a 12-fold increase of a different procoagulant activity which appears to be a direct prothrombin activator. This prothrombinase was calcium dependent and was inhibited by 2.5 mM diisopropylfluorophosphate, but was not neutralized by anti-Factor X antibodies or by inhibitors of Factor Xa. In contrast to the other lipoprotein density classes, low density lipoprotein did not stimulate procoagulant activity, but instead actively suppressed the generation of the two procoagulant activities induced by the stimulatory lipoproteins. Suppression by low density lipoprotein was clearly evident at molar ratios of low density lipoprotein to stimulatory lipoproteins of 1:3 or less. Reconstitution of all lipoproteins to physiological concentrations was not stimulatory as a consequence of the suppressive effects of low density lipoprotein. These data indicate that isolated plasma lipoproteins are capable of regulating the expression of two different procoagulant activities of peripheral blood mononuclear cells in vitro. The possibility that these interactions may be implicated in the association between certain types of hyperlipoproteinemias and thromboembolic disease merits study.

Oral contraceptives and responsiveness of plasma renin activity and blood pressure in normotensive women

In young normotensive women (5 without and 5 with chronic oral contraceptives (= o.c.) cardiovascular homeostasis was challenged by isoproterenol and ergometer exercise, at normal and at resitricted sodium intake. Blood pressure and plasma renin activity (= PRA) did not differ between the 2 groups. Plasma renin substrate was markedly elevated in the o.c. group. Sodium restriction induced similar changes in body weight, urinary sodium excretion, systolic blood pressure and PRA; diastolic blood pressure decreased only in the non-o.c. group (by 6 mm Hg). In both groups isoproterenol and exercise induced similar changes in heart rate and blood pressure, except that after sodium restriction both stimuli caused larger decreases in diastolic blood pressure in the o.c. group. At both levels of sodium intake, PRA increased slightly less during exercise in the o.c. group; following restriction PRA response to isoproterenol was significantly less in the o.c. group. These results indicate that following chronic use of o.c. PRA responsiveness is normal or somewhat blunted. The different responses of diastolic blood pressure to sodium restriction and subsequent isoproterenol or exercise point to subtle changes in the inter-action of aodium and pressor mechanisms during chronic o.c. use.

[Metabolic studies under administration of oral contraceptives. A review]

The use of oral contraceptives can produce changes in the metabolism of carbohydrates, lipids, proteins, vitamins, and minerals. Responsible for the alterations seems to be the used oestrogen- and gestagen derivative and not so much the type of the contraceptive. The most frequent findings are raised serum-glucose-, insulin-, and triglyceride levels; disturbances in protein-metabolism increase the risk of developing thrombosis and hypertonia. Little is known about the significance of oral contraceptives on the vitamin- and mineral metabolism--yet extreme deficiencies have not been observed so far. Oral contraceptives can become an extra risk factor when given to women with metabolic disturbances.

Estrogen receptor in the mammalian liver

The cytosol from livers of adult female mammals contains [3H]estradiol-binding proteins that can translocate to the nucleus and attach to chromatin. In comparison to the prepubescent rat, adults have higher estrogen binding in the liver and greater increases in plasma renin substrate after administration of estrogen. The protein in the liver which binds estrogen may be an estrogen receptor involved in modulating hepatic synthesis of selective plasma proteins.