Hypocalcemia and Increased Serum Calcitonin in Baby Rats Given Glucose Orally

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Abstract
Baby rats, 15 days old, were fasted > 13 h and given 1.5 ml 5% glucose by stomach tube. Control babies were gavaged with 1.5 ml 0.9% NaCl which itself did not affect serum Ca or CT. Gavage with glucose produced a fall in serum Ca of 0.5-1.0 mg/dl 60 min later (P < 0.05-< 0.005). Glucose produced a fall in serum P at 60 min similar to that in serum Ca. Measurement of immunoreactive CT in serum showed a significant rise from .apprx. 120 pg/ml or less up to as much as 900 pg/ml (P < 0.01). A time course study showed that serum CT increased and serum Ca decreased only at 60 min after oral glucose; values had not changed at 30 min and had returned to control levels by 90 min. In contrast, serum glucose was high (.apprx. 300 mg/dl) at 30 min after gavage and had returned toward the control level (.apprx. 130 mg/dl) by 60-90 min. The decrease in Ca after glucose must, at least in part, be due to CT since after thyroidectomy glucose did not produce a significant fall in serum Ca. Oral administration of a Ca-free solution can increase CT release in the absence of a rise in blood Ca.