Glucose-Stimulated Insulin Secretion in Rats with Normal Plasma Calcium Levels: Effects of Calcium Deficiency

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Abstract
Weanling Wistar rats were pair-fed for 9 days a control or a calciumdeficient diet. After a 12-hour fast the rats were injected intraperitoneally with glucose (250 mg/100 g body weight), and blood was collected 15, 30 and 60 minutes after the injection. Before injection, calcium (9.7 ± 0.2 mg/100 ml), glucose and insulin plasma levels were identical in the control and deficient animals, although calcium-deficient animals showed a small but significant increase in blood plasma magnesium levels. Blood glucose levels were higher in the calcium-deficient rats than in control rats 15 to 30 minutes after the glucose injection (15.4 ± 1.4 vs. 9.7 ± 0.4 mM, P < 0.01, 30 minutes after). Plasma insulin levels were significantly lower 15 minutes after the glucose injection (24 ± 4 vs. 73 ± 8 µU/ml; P < 0.01). Calcium deficiency is therefore associated with a decreased response to the glucose tolerance test in the absence of any change in the blood plasma calcium levels.