INTERCONVERSIONS OF ESTROGENS AND RELATED DEVELOPMENTAL EFFECTS IN SAND DOLLAR EGGS

Fertilized eggs of the sand dollar, Dendraster excentricus, are blocked from normal development by low concentrations of 17 β-estradiol (3.7 μm) and diethylstilbestrol (0.24 μm), but not by comparable levels of cortisol, corticosterone, and androstenedione, or higher concentrations (59 μm) of estrone, testosterone, and progesterone. The blockage is apparently due to incomplete development of astral and spindle fibers. Protein synthesis is not affected. Radioactive steroids were used to show that fertilized eggs bind estradiol, estrone, testosterone, and progesterone, and that unfertilized eggs bind less estradiol than those that are fertilized. Most of the bound steroid resists extraction with chloroform, but small fractions are recovered by this method. Analyses of recovered steroids indicate that estradiol and estrone and interconverted by the eggs. Although estrogens and other steroids are found in reproductive tissues of various invertebrates, levels used in this study are unphysiological. The results are of interest because they might be related to mechanisms by which development is inhibited by estrogens. © 1969.