Sex-related differences in the effect of aluminum on calcium transport in the small intestine of the rat

Everted sacs of distinct segments of small intestine from male and female rats were incubated with 2 mu M of aluminum (Al). In duodenum, Al significantly diminished calcium flux (JCa(ms)) in cycling females (31%, P < 0.01) and in males (17%, P < 0.05). Incubation under anaerobic conditions nullified the inhibition of Al on JCa(ms) both in male and in female duodenal sacs. Jejunal and ileal JCa(ms) measured under aerobic conditions were not modified by the presence of Al in mucosal fluid compared to Al-free controls, neither in males nor in cycling females. In ovariectomized female rats treated with estrogen the studies of dose-response curves showed that the sensitivity to the effect of Al on JCa(ms) was raised (the dose that produced half maximum response diminished) with increasing 17 beta-estradiol serum levels, without changes in the maximum response. In castrated male rats injected with testosterone, the effect of Al on duodenal JCa(ms) was found to be independent of testosterone levels. In summary, our results demonstrated that the Al inhibition on duodenal JCa(ms) was influenced by sexual hormone levels in females but was independent of them in males.