Endocrinology
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Comparative Study
Differential effects of parathyroid hormone on the renal 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 production of young and adult rats.
In young rats, PTH markedly stimulates the renal conversion of 25-hydroxyvitamin D3 (25OHD3) to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], the biologically active form of vitamin D3. With increasing age, serum 1,25-(OH)2D3 decreases while serum PTH increases. Therefore, the effect of PTH on the renal metabolism of 25OHD3 to 24,25-(OH)2D3 or 1,25-(OH)2D3 was compared in young and adult rats. ⋯ The PTH-stimulated increase in the cAMP content of renal slices from adult rats was 75% that of slices from young rats. These studies demonstrate that PTH modulates renal 24,25-(OH)2D3 production in the adult. However, PTH does not modulate renal 1,25-(OH)2D3 production in the adult under the same conditions that produce a PTH effect in the young animal.