BINDING OF STRONTIUM VS CALCIUM TO 17-BETA-ESTRADIOL-INDUCED PROTEINSIN THE PLASMA OF THE GOLDFISH CARASSIUS-AURATUS

The binding of Sr to estradiol-induced proteins (EIP) was studied 7 da ys after a single injection of 17 beta-estradiol (E-2) into goldfish e xposed to Sr-enriched water (5, 10, and 15 mg/l). E-2 induced hypercal cemia in a way that was negatively correlated with ambient Sr concentr ation and hyperstrontemia in a way that was positively correlated with the concentration. Diffusible Ca concentrations in plasma remained un changed in the estrogenized and control fish, while diffusible Sr conc entrations increased with an increase in ambient Sr concentration in b oth the experimental and control fish. Protein-bound Ca and Sr concent rations in plasma were always higher in the estrogenized fish than in the control fish and their levels decreased and increased, respectivel y, depending on the ambient Sr concentration. The ratios of EIP-bound Sr to EIP-bound Ca increased with an increase in the Sr concentration. These results suggest that Sr competes with Ca for binding to vitello genin in estrogenized goldfish.