Comparison of effects of verapamil, low calcium diet and betamethasone on duodenal calcium absorption efficiency in the chick.

The results indicate that oral administration of verapamil for 2 weeks to the chick is followed by an increase in the efficiency of the duodenal absorption of calcium. In these chicks both a decrease in serum calcium level and an increase in the activity of renal 1 alpha-hydroxylase were observed. The increased calcium absorption following prolonged treatment with verapamil resembles that induced by a low calcium diet. The mechanism of both responses presumably involves an increased production of 1,25-dihydroxyvitamin D3. Both verapamil- and low calcium diet-induced adaptations are capable of overcoming the inhibitory action of betamethasone on intestinal calcium absorption. No effects on calcium absorption were noted if verapamil was administered intraperitoneally which suggests that verapamil exerts its action directly on the intestinal mucosa.