Reversal of skeletal resistance to parathyroid hormone in uremia by vitamin D metabolites: evidence for the requirement of 1,25 (OH) 2D3 and 24,25 (OH) 2D3
Massry, S.G.; Tuma, S.; Dua, S.; Goldstein, D.A.
Journal of Laboratory and Clinical Medicine 94(1): 152-157
1979
ISSN/ISBN: 0022-2143 PMID: 469372 Document Number: 150491
Changes in serum calcium after infusion of parathyroid extract 2 U/kg h for 8 h were evaluated in thyroparathyroidectomized dogs before and after 1 and 3 days of acute uraemia produced by bilateral nephrectomy. The dogs were given vitamin D metabolites during the 3 days of uraemia. Supplements of 0.68 mu g 1,25-dihydroxycholecalciferol (DHCC) and 24R,25-DHCC daily restored the calcaemic response to parathyroid extract to normal, in contrast to only partial correction of the response to parathyroid extract by 1,25-DHCC alone. Administration of 1.36 mu g 24R,25-DHCC daily did not improve the calcaemic response to parathyroid extract. The results indicate that 1,25-DHCC and 24R,25-DHCC are necessary for the complete reversal of the impaired calcaemic response to parathyroid extract, that this effect is not due to the increase in the amount of the dihydroxylated compounds of vitamin D, as equivalent amounts of these compounds in the form of 24R,25-DHCC alone had no effect, and that the better effect of the combination of 1,25-DHCC and 24R,25-DHCC is most probably due to an interaction between these two metabolites of vitamin D permitting an intact calcaemic action of parathyrin.