Abstract
Summary
The influence of gastrin on calcium (Ca) homeostasis was investigated in anesthetized rats. When administered intraperitoneally, gastrin was found to lower plasma Ca concentration in both intact rats and rats which had their source of calcitonin removed (thyroparathyroidectomized) but to exert no significant effect on the rates of urine Ca excretion in the intact rats. Thus, its hypocalcemic effect was independent of calcitonin. In search of possible routes of Ca removal from the blood, both the Ca concentration in gastric juice and the total gastric Ca excretion were measured. Total gastric calcium excretion increased from 14 ± l.4 to 22 ± 2.4 μg/hr/100 g rat by the administration of gastrin. The increase in gastric Ca secretion and the hypocalcemic effect were abolished by concurrent administration of secretin (2 units). The bile volume and the Ca content in the bile secretion were not affected by gastrin. These findings were compatible with the hypothesis that the hypocalcemic effect of gastrin was partly caused by an increased Ca excretion into the gastrointestinal lumen.
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