Regulation of calcium metabolism in streptozotocin-induced diabetes

Abstract

Female Wistar rats [69 days-old] that were made diabetic 9 days earlier, by an i.p. injection of streptozotocin, were studied by a combination radioisotope and balance technique that evaluates Ca absorption, excretion and bone Ca deposition and resorption rates. Streptozotocin-induced diabetes was associated with a marked drop in Ca absorption and a 3-fold rise in urinary Ca excretion, changes that greatly exceed the expected effects from the hyperphagia and increased Ca intake of the experimental animals. Bone Ca deposition was halved in the diabetic rats, with bone resorption unchanged and equal to the deposition rate. The bone and body Ca balances were 0 in the experimental animals. To maintain plasma Ca near normal under these circumstances, the diabetic animals turned over their skeletal Ca, in relationship to the central pool, much more rapidly than the controls. Although the skeleton in the normal animals serves as both storehouse and regulator of the plasma Ca, in short-term streptozotocin-induced diabetes there is no Ca storage in bone, with the skeleton only playing the role of regulator of Ca homeostasis.