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In view of the lack of sufficient data regarding the morphology of the cystic duct and the extensive focus on the gallbladder, a preliminary examination of the cystic duct response to female sex steroid treatment was conducted to follow up a detailed ultrastructural study of the gallbladder epithelial response to a similar treatment. As observed in the gallbladder epithelium, the cystic duct epithelial cells of nulliparous Syrian hamsters demonstrate morphologic changes in response to female sex steroid treatment. Control (C) cystic duct epithelial cells are covered by short microvilli and each cell appears to exhibit a single vestigial cilium. Estrogen (E)- and estrogen + medroxyprogesterone (E + MP)-treatments induce differential duct cell morphologic changes. These changes are the result of steroid treatments in the significant decreasing sequence E > E + MP > C for nuclear volume, indentations and perinuclear lysosomal/lipofuscin bodies. Moreover E + MP-treatment results in larger cytoplasmic volume and more sloughing of apical cell excrescences than following E treatment. It is suggested that, similar to that in the gallbladder, the action of progestin is paramount in favoring cytoplasmic morphological changes in the cystic duct which, along with the alteration of mucus, cell sloughing, decreased bile acids and motility could also participate in the gallstone nucleation process as they are brought into the gallbladder with the incoming bile flow.

Ovariectomized Syrian hamsters treated by female sex steroids during a 1-month period show gallbladder surface epithelial changes in the fundic area consistent with apical bulging and decapitations of the epithelial cells. These events were detected in the infundibulum and the fundic or body regions of estrogen- and estrogen + progesterone-treated hamsters. In control hamsters, these events were restricted to the region in the vicinity of the bile duct. Following steroid treatment, intraluminal deposits detected resembled Ca-bilirubinate deposits described in previous studies while decapitations are similar to endometrial epithelium changes associated with hormonal physiological changes or treatments. Moreover some small electrondense deposits are comparable to those found in human cholesterol gallstones. This report indicates that, besides an alteration in bile composition, cell fragments originating from the surface epithelium of the bile duct and/or of the gallbladder mucosal epithelium could participate in gallstone nucleation.