Calcium adenosine triphosphatase and secretion of koilin membrane in the gizzard of the fowl.

The localization of calcium adenosine triphosphatase (Ca(2+)-ATPase) was determined histo- and ultracytochemically in the gizzard gland cells of the adult domestic fowl. Surface and chief gland cells exhibited faint and inconstant basolateral activity in contrast to basal cells, whose basolateral cell membrane constantly showed deposition on the external side. Intracellular enzyme activity was localized on the luminal aspect of Golgi membranes in all types of gland cells. Lysosomes also reacted positive for Ca(2+)-ATPase. Neither membranes of secretory vesicles nor cortical cytoplasm of the secretory pole exhibited enzyme activity. From these results it is speculated that calcium is not essentially involved in the secretion of the koilin membrane in terms of storage of the secretory material, transport to the secretory surface and release into the lumen. Ca(2+)-ATPase activity rather seems to be related to differentiation and maturation processes and to intracellular storage of Ca2+.