Widespread distribution of calcium pump in calcium-transporting tissues. Immunohistochemical studies.

We examined the distribution of the plasma membrane calcium pump in several calcium-transporting tissues. Epitopes of the pump were found in the human kidney, specifically in the basolateral membrane of the distal tubule. The 28-kD calcium-binding protein co-localized with the calcium pump in cells of the distal tubule. Other human tissues that contain calcium pump epitopes include the basal surface of the syncytiotrophoblast of the placenta, human osteoblast-like cells and human choroid plexus. In the rat, calcium pump epitopes were found in the distal tubule of the kidney, the duodenum, the ileum, jejunum, placenta and in the choroid plexus. The pump is widely distributed in various calcium-transporting tissues and probably plays an important role in the translocation of calcium.