Thromboxane production in the blood of women increases after menopause whereas tumor necrosis factor is reduced in women compared with men.

ABSTRACT

Previously we have shown that incubation of heparinized blood with a low dose of lipopolysaccharides (5 ng/ml) resulted in a 60% higher generation of TxB2 in the blood of young men as compared with that of young women. In the present study, we investigated a group consisting of 38 healthy men and 38 healthy postmenopausal women aged 50-73 years with no drug use and no known chronic disease. In contrast to our earlier observation that young men produce more TxB2 than young women, no significant difference was observed between the men and women when all the participants above 50 years of age were included (5.7 +/- 0.6 ng/l for men versus 5.2 +/- 0.7 ng/l for women). However, a strong correlation was found with simple regression analysis when increasing TxB2 generation was compared with years after menopause (P < 0.0001). No such correlation was observed for increasing age of men and their TxB2 production. The LPS stimulation system of whole blood was also used to evaluate the production of tumor necrosis factor (TNF-alpha) in older people. Men were found to generate 60% more TNF-alpha than women, but no correlation was found between increasing age of women and TNF-alpha production as observed with TxB2. Risk factors such as SDS-cholesterol, fibrinogen and factor VII were the same in men and women, whereas total cholesterol was higher in women than in men (P < 0.05). Since TxA2 is known to be a mediator of atherosclerotic-induced lesions and TNF-alpha is a well-established indicator of inflammatory reactions, we propose that the reduced production of TxB2 and TNF-alpha in women in our model system may partially explain the lower incidence of atherosclerosis in women as compared with men, and the phenomenon of increased incidence of this disease after menopause.