Regulation of calf renal 25-hydroxyvitamin D-hydroxylase activities by calcium-regulating hormones

J Dairy Sci. 1987 Nov;70(11):2266-71. doi: 10.3168/jds.S0022-0302(87)80286-2.

Abstract

Parathyroid hormone and 1,25-dihydroxyvitamin D3 had opposite effects on calf renal 25-hydroxyvitamin D3 24-, 23-, and 1 alpha-hydroxylase activities. Parathyroid hormone administration increased renal 25-hydroxyvitamin D3-1 alpha-hydroxylase activity 7-fold while 25-hydroxyvitamin D3-23- and 24-hydroxylase activities were essentially the same as controls. Administration of 1,25-dihydroxyvitamin D3 increased 25-hydroxyvitamin D3-23-hydroxylase and 24-hydroxylase activities 4-fold and decreased 25-hydroxyvitamin D3-1 alpha-hydroxylase activity to undetectable concentrations. Vitamin D deficiency increased 25-hydroxyvitamin D3-1 alpha -hydroxylase activity 13-fold, and 25-hydroxyvitamin D3-23-hydroxylase and 24-hydroxylase activities were undetectable. These results confirm previous reports with regard to control of renal 25-hydroxyvitamin D3-24-hydroxylase and 1 alpha -hydroxylase in other species and represent new findings relative to the control of 25-hydroxyvitamin D3-23-hydroxylase. Plasma P was lower and 1,25-dihydroxyvitamin D3 higher in calves treated with parathyroid hormone, and Ca and 1,25-dihydroxyvitamin D3 were lower in the vitamin D-deficient calves. 1,25-Dihydroxyvitamin D3-treated calves had higher plasma P and lower Mg than controls. Further studies using this calf model should lead to better understanding of Ca-regulating hormones control of vitamin D metabolism.

MeSH terms

  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase / metabolism*
  • Animals
  • Calcitriol / pharmacology*
  • Cattle / metabolism*
  • Cytochrome P-450 Enzyme System*
  • Kidney / drug effects
  • Kidney / enzymology*
  • Male
  • Parathyroid Hormone / pharmacology*
  • Steroid Hydroxylases / metabolism*
  • Vitamin D3 24-Hydroxylase

Substances

  • Parathyroid Hormone
  • Cytochrome P-450 Enzyme System
  • Steroid Hydroxylases
  • Vitamin D3 24-Hydroxylase
  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase
  • Calcitriol