[Calcium metabolism in dogs].

Calcium homeostasis is controlled both directly and by hormones. Directly as a result of the fact that the uptake of calcium from the intestine and its excretion by the intestine, kidney and skeleton are well attuned to one another. A process of diffusion of calcium through the intestinal wall occurs in addition to active absorption of calcium, particularly in young animals. The maximum excretion of calcium by the kidneys is one per cent of the amount of circulating calcium. The skeleton acts as a calcium buffer in which 99.5 per cent of the body calcium is present. As regards hormones, the calciotropic hormones (parathormone, calcitonin and vitamin D) are the most important factors, which particularly affect the processes of absorption, resorption and accretion of calcium. The effects on the excretion of calcium are very slight. The system of calcium homeostasis is designed to maintain a normal level of calcium in blood (dog less than twelve months: 2.5-2.9 mmol/l; dog greater than twelve months: 2.2-3.0 mmol/l). A prolonged abnormal calcium intake will result in skeletal changes, particularly in young dogs. Inhibition of remodelling reconstruction of the skeleton and disturbance of enchondral ossification, which became clinically apparent, among other things, in the canine Wobbler syndrome and osteochondritis dissecans, were observed in Great Danes dogs having a high calcium intake. A low calcium intake in Great Danes dogs resulted in osteoporosis and pathological fractures without any impairment of enchondral ossification being observed.(ABSTRACT TRUNCATED AT 250 WORDS)