Calcium metabolism in relation to vitamin D and adrenal function in the chick

¹ Department of Biochemistry, University of Adelaide, Adelaide, South Australia

The influence of certain adrenal and synthetic steroids on calcium absorption has been tested in rachitic or vitamin D₃-treated rachitic chicks. Long-term (3-day) administration of cortisol or deoxycorticosterone (DOC) interfered with the enhancement of Ca transport generally brought about by vitamin D₃. The steroids had no effect on absorption by rachitic chicks. The effect was not a direct antagonism of the vitamin D₃ effect, since cortisol, ' cortisol, or DOC enhanced the vitamin D₃ effect when the steroids were injected intracardially 1 hr before the test. The effects can be correlated with interference of adrenal function when cortisol or DOC are administered for long periods. The theory is proposed that vitamin D₃ is transformed into its active form in the adrenal cortex. Use of the specific inhibitor, 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2, 2-dichloroethane, to interfere with adrenal function showed that this substance, when given for 3 days prior to the test, would eliminate the enhancement of Ca transport usually brought about by vitamin D₃.

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