Oral contraceptive and Platelet lipid biosynthesis in female rats: dose-response relationship

Oxidative status and oral contraceptive. Its relevance to platelet abnormalities and cardiovascular risk

Oral contraceptive (OC) use is a risk for thrombogenic events. This paper reviews effects of OC on oxidative status, coagulation, and platelet activity. Complicating effects of cardiovascular risk factors such as smoking, diabetes, hyperpidemia, and hypertension, are discussed. From these data we conclude that: 1. OC use modifies slightly but significantly the oxidative status in women and in animals by decreasing in plasma and blood cells the antioxidant defenses (vitamins and enzymes). 2. The changes in the oxidative status are related to an increase in plasma lipid peroxides apparently responsible for the hyperaggregability and possibly the imbalance in clotting factors associated with the OC-induced prethrombotic state. 3. These effects of OC appear to be increased by a high intake of polyunsaturated fat and counteracted by supplements of vitamin E. 4. The risk factors acting synergistically with OC, have all been shown to increase platelet reactivity. In addition, smoking, diabetes, and, to some extent, dyslipidemia are associated with an increased level of lipid peroxides and concomitant changes in the antioxidant defenses that can be additive to those induced by OC. Thus, free radicals and lipid peroxidation could be the underlying mechanism in the predisposition to thrombosis induced by most risk factors in OC users. 5. Results of epidemiologic and experimental studies in this field will be concordant only when diet and natural antioxidants will be systematically taken into consideration.

Steroidal contraceptives and changes in individual plasma phospholipids: possible role in thrombosis

The changes in the levels of individual phospholipids were studies in women during prolonged use of three types of steroidal contraceptive preparation: high-dose combined pills (Noriday 1 + 50 Fe); low-dose combined pills (Nominest Fe) and progestin-only injectables (Depo-Provera). Women on high-dose combined pills had significantly higher (p less than 0.05) mean lysophosphatidylcholine (LPC), sphingomyelin (SPH), phosphatidylserine (PS) and phosphatidylethanolamine (PE) levels, respectively, than the women on low-dose combined pills, progestin-only injectables and the controls, respectively. Women on low-dose combined pills had significantly lower (p less than 0.01) mean LPC and PS levels, respectively, than the controls, while women on progestin-only injectables had significantly lower (p less than 0.01) mean PS and PE levels, respectively, than the controls. Based on the reported high activities of PS and PE in hemostasis, the PE/total plasma phospholipids, PS/total plasma phospholipids and the sum of PE and PS/total plasma phospholipids ratios were calculated to assess the possible overall effect of the changes in plasma phospholipids in steroidal contraceptive users. The results obtained using these indices agree with some earlier reports of an estrogen dose-dependent risk/incidence of thrombosis in steroidal contraceptive users. It is concluded that the observed dose-dependent estrogen-induced alterations in phospholipids, and, most especially, the PE and PS fractions may bear a relationship with thrombotic conditions.

Influence of sex and dietary fats on platelet lipid biosynthesis in rat

The platelet biosynthesis of total lipids, lipid fractions and fatty acids was determined by incorporation of [14C]acetate in normal and castrated rats of both sexes. Comparison was made between animals fed laboratory chow alone, and animals receiving, in addition, for 4 days by stomach tube a saturated (cream) or polyunsaturated (sunflower seed oil) fat. In male rats, the polyunsaturated fat increased slightly the total platelet lipid biosynthesis. The saturated fat drastically reduced it by 43% in comparison to the polyunsaturated fat-fed animals. Normal female rats did not exhibit a similar difference in the platelet lipid synthesis. However, the inhibitory effect of saturated fat on lipid synthesis could be observed in castrated females, although it was less pronounced (27% reduction) than in castrated or normal males (43%). Administration to castrated males of estradiol for 1 month almost completely inhibited the difference induced by the feeding of the different fats in the lipid platelet synthesis of male rats. This difference in the platelet lipid biosynthesis between male and female rats, normal and castrated, was observed mostly in the phospholipid (especially phosphatidylcholine), monoacylglycerol and triacylglycerol fractions and affected primarily the synthesis of the three main saturated fatty acids, 14:0, 16:0 and 18:0. Thus, it seems that, in rat, the short-term administration of a saturated fat induces drastic changes in the platelet lipid biosynthesis, but only in males. The protection observed in females appears to be essentially dependent upon estrogens.