Subcellular localization of Ca-ATPase and calcium in Bufo arenarum oviducts

The localization of calcium and Ca-ATPase activity in Bufo arenarum oviduct s was investigated by ultrahistochemical techniques during the sexual cycle . In the preovulatory period prominent calcium deposits were detected in th e secretory granules of epithelial and glandular cells as well as in close proximity to the plasma membranes. Furthermore, intense Ca-ATPase activity was found outlining the plasma and secretory granule membranes. Regional di fferences along the oviduct were observed. Immediately after ovulation the above-mentioned cells exhibited a marked reduction of calcium deposits and Ca-ATPase activity, but during hibernation this situation progressively rev erted. These results demonstrate that the most prominent calcium deposits c an be detected in the cellular structures that, through different secretion mechanisms, release their products towards the oviductal lumen to form the structural network of the jelly coats. The variations in calcium contents in the oviduct and the animal cycle changes in serum calcium levels are clo sely related with the fluctuations of estradiol serum levers during the sex ual cycle, suggesting hormonal regulation.