Raised levels of calcium-binding protein in plasma following insulin-induced hypoglycaemia in the pig.

Insulin-induced hypoglycaemia in the pig elicited sharp increases in the plasma concentrations of vitamin D-dependent calcium-binding protein (CaBP) and cortisol and a decrease in plasma inorganic phosphate. Glucose infusion following insulin administration abolished the increases in plasma CaBP and cortisol in response to insulin and reduced the hypophosphataemia. The percentage increases in plasma CaBP and cortisol in response to insulin-induced hypoglycaemia were reduced when the pigs were fed a low-calcium diet, but the hypophosphataemic response was similar. We conclude that insulin-induced hypoglycaemia leads to increased plasma CaBP in pigs fed a normal calcium diet, which is associated with the hypoglycaemia rather than being a direct effect of insulin. We therefore suggest that plasma CaBP may represent more than a mere uncontrolled leak from its sites of storage.