Calcium metabolism in relation to chronic ethanol ingestion and estrogen deficiency in rat

The plasma calcium concentration, urinary calcium excretion, total bone calcium content and the rate of calcium uptake and release by tibias were measured in 6 groups of rats which were kept under various treatment protocols for 8 wk. Ovariectomy led to significant hypocalcemia and a decrease in bone calcium content; the former being reversed towards normal by estrogen treatment. Chronic ethanol ingestion reduced the bone calcium content without apparent effect on plasma calcium in intact rat and further reduced (P less than 0.05) the bone calcium content in ovariectomized rats. The calcium uptake by the bone measured by 45Ca injected ip at zero hour was the same among the 6 groups. When 45Ca was injected ip 17 hours earlier, the disappearance of plasma 45Ca was found to be slower in ovariectomized and alcohol treated groups, indicating a higher rate of calcium movement from bone to plasma. Moreover, there was also an increase in the rate of calcium release by tibias after ovariectomy and chronic alcohol ingestion; the release was slightly greater in the condition of ovariectomy plus alcohol. The present investigation thus, provides evidence that ethanol is likely to have a direct stimulatory effect on bone resorption as well as an indirect effect through disrupting ovarian function during chronic administration.