Postmenopausal estrogen and androgen replacement and lipoprotein lipid concentrations.

The effect of a combined estrogen-androgen drug on the lipoprotein lipid profile of women who received it parenterally as long-term postmenopausal replacement therapy was compared to that of women who had been receiving estrogen alone parenterally and to untreated surgically menopausal women. Plasma estradiol, testosterone, total cholesterol, triglycerides, high-density lipoproteins, and low-density lipoproteins were measured at baseline (55 days after injection) and then on days 2, 4, 8, 15, 21, and 28 after injection. The plasma estradiol levels were greater in the two hormone-treated groups compared with the control group (p less than 0.01), and plasma testosterone levels of the combined group exceeded those of the other two groups (p less than 0.01) and remained above the normal female range for the duration of the study. There were no between-group differences in total cholesterol, triglycerides, high-density lipoprotein, or low-density lipoprotein values. Neither was the low-density/high-density lipoprotein ratio significantly different between groups at any of the test times. Therefore, the addition of testosterone to a long-term parenteral estrogen replacement regimen did not induce an increased atherogenic lipid profile compared with that produced by the parenteral administration of estrogen alone.

Relation between insulin and glucose flux rates in the dog.

A constant infusion isotope dilution procedure for measurement of plasma insulin flux rates was performed in acutely eviscerated dogs receiving an infusion of nonlabeled insulin; the calculated rate of insulin flux corresponded closely to that of the administered rate, thus validating the isotope dilution procedure. Flux rates of insulin and glucose were measured simultaneously at different steady levels in intact dogs. There was a linear relationship between plasma insulin concentration and insulin flux rate. In each animal there was also a linear relationship between glucose flux rate and insulin concentration, and between rates of glucose flux and insulin flux, but there was considerable inter-animal variation in the slope of the regression lines.