Further findings on the inhibitory effect of estradiol benzoate on the circulation and on 45Ca and 3H-proline incorporation in rat bones.

Various aspects of the effect of estradiol benzoate (EB, Agofollin Depot, Czechoslovakia, usually in a s.c. dose of 5 mg/kg body weight once a week), on the local circulation (the uptake of 85Sr-microspheres), the incorporation of 45Ca and 3H-proline, bone density and ash weight related to bone volume were studied in six experiments in the tibia and distal femur of 224 rats. 1. The dose-response. In rats treated four weeks with doses of 0.5, 1.0, 1.5 and 2.0 mg EB per rat once a week, a significant correlation with the uptake of 85Sr-microspheres (r = -0.56), the blood flow (r = -0.56), the incorporations of 45Ca (r = -0.89) and 3H-proline (r = -0.35) and body weight (r = -0.71) was demonstrated. 2. The time course of changes after 1, 2, 4 and 8 weeks administration of EB. Circulatory values were not significantly lowered until after four weeks, 45Ca incorporation and body weight were significantly lower after only one week and 3H-proline incorporation did not fall until after eight weeks. The course of the uptake of 85Sr-microspheres and the incorporation of 45Ca were very similar. 3. Comparison of males and females. EB reduced circulatory values and 45Ca and 3H-proline incorporation and increased bone density and bone ash weight in both males and females. Conclusions. The decrease in the local bone blood flow after EB showed a significant dose-effect correlation; the decrease in circulatory values, on using the given administration method, is significant after four weeks. The inhibitory effect of EB on the bone blood flow is not sex-specific.(ABSTRACT TRUNCATED AT 250 WORDS)