Calcium-ATPase activity in erythrocyte ghosts from patients with familial benign hypercalcaemia.

It has been suggested that the parathyroid glands and the kidneys are insensitive to the high extracellular calcium levels found in familial benign hypercalcaemia (FBH) (familial hypocalciuric hypercalcaemia) and that there may be a general disorder of the plasma membrane 'calcium pump'. We have found that the activity of the calcium-stimulated, magnesium-dependent ATPase of erythrocyte ghost membranes from patients with FBH was significantly higher (p less than 0.01) than that from normal subjects. Values in FBH, as a group, were higher than those in primary hyperparathyroidism, but the difference was not significant. We suggest that the membrane abnormality in FBH could be a disorder of the regulation of the calcium pump.