Abstract
Summary
Baby rats, 15 days old, were fasted > 13 hr 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 calcium or CT.
Gavage with glucose produced a fall in serum calcium of 0.5-1.0 mg/dl 60 min later (P < 0.05-<0.005). Glucose produced a fall in serum phosphorus at 60 min similar to that in serum calcium. Measurement of immunoreactive CT in serum showed a significant rise from ~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 calcium 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 (~300 mg/dl) at 30 min after gavage and had returned toward the control level (~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 calcium.
The findings show that oral administration of a calcium-free solution can increase CT release in the absence of a rise in blood calcium.
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