The relationship between diet and estrogens was studied in two groups of women with different dietary habits and breast cancer risks. Plasma estrogens and androgens and 24-h urinary and fecal excretion of estrogens were measured in premenopausal and postmenopausal Caucasians and recent Oriental immigrants from Southeast Asia to Hawaii. Premenopausal Caucasians had 30-75% higher plasma estrone and estradiol levels than their age-matched cohorts in Hawaii, and the postmenopausal Caucasians had 3-fold higher plasma levels of estradiol. The Oriental women excreted more than twice the amount of estrogen in their feces but they excreted significantly less in their urine. Thus, the ratio of urinary-to-fecal excretion was approximately 3-5 times higher in young Caucasian women. Analysis of dietary components and plasma estrogens in premenopausal women showed a positive correlation between daily intake of total fat and saturated fat and plasma estrone and estradiol concentrations.

Ouabain binding by the human erythrocyte membrane is reversible, exhibits a high degree of chemical specificity, and can be detected at ouabain concentrations as low as 1 X 10-1 0 M. The relation between ouabain binding and ouabain concentration can be described by a rectangular hyperbola permitting determination of the maximal binding (Bma) and the ouabain concentration at which ouabain binding is half-maximal (KB). Reducing the external sodium concentration increased KB, while reducing the external potassium concentration decreased KB . Neither cation altered Bmax. The reciprocal of KB was a linear function of the sodium concentration at sodium concentrations ranging from 0 to 150 mM. Conversely, the relation between the reciprocal of KB and the external potassium concentration was nonlinear, and raising the potassium concentration above 4 mM produced no further increase in KB. These results are compatible with a model which postulates that the erythrocyte membrane contains a finite number of receptors each composed of a glycosidebinding site and a cation-binding site. When sodium occupies the cation-binding site, the affinity of the glycoside site for ouabain is increased; when potassium occupies the cation-binding site the affinity of the glycoside site for ouabain is decreased.

A B S T R A CT COOH-terminal octapeptide of cholecystokinin (CCK-octapeptide)

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