Fluorescent antibody localization of the vitamin D-dependent calcium-binding protein in the oviduct of the laying hen.

Fluorescein isothiocyanate-conjugated sheep antirabbit gamma-globulin was used in the indirect fluorescent antibody technique to localize the vitamin D-dependent calcium-binding protein (CaBP) in the shell gland of the laying hen. Intense specific fluorescence, indicative of the presence of CaBP, was found only in the tubular gland cells and not in the surface epithelium. CaBP was primarily associated with the luminal surface and other cell boundaries, and in lesser concentrations within the cells except for occasional intracellular regions of high concentration. The magnum, isthmus and vagina were essentially negative. Since the concentrations of intestinal CaBP is highly and directly correlated with the efficiency of calcium absorption, the present results suggest that the tubular gland cells might have a primary role in the transport of calcium associated with egg shell formation.