Plasma concentrations of 1,25-dihydroxyvitamin D, 1,24R,25-trihydroxyvitamin D3, and 2,25,26-trihydroxyvitamin D3 after their administration to dairy cows

J Dairy Sci. 1983 Jul;66(7):1455-60. doi: 10.3168/jds.s0022-0302(83)81959-6.


Intramuscular administration of 1,25 (R or S),26-trihydroxyvitamin D3 to dairy cows resulted in significant elevation of 1,25-dihydroxyvitamin D3 concentration in blood plasma. The increase of 1,25-dihydroxyvitamin D3 in plasma paralleled the increase of 1,25,26-trihydroxyvitamin D3. We also found that intramuscular 1,25-dihydroxyvitamin D3 administration to dairy cows significantly elevated plasma 1,24,25-trihydroxyvitamin D3. These data suggest possible impairment of 1,25-dihydroxyvitamin D3 metabolism during the presence of pharmacologic concentrations of 1,25,26-dihydroxyvitamin D3 in plasma. In addition, the 24-hydroxylation of 1,25-dihydroxyvitamin D3 to 1,24,25-trihydroxyvitamin D3 appears to be an important route for further metabolism of 1,25-dihydroxyvitamin D3 in dairy cows.

MeSH terms

  • Animals
  • Calcitriol / administration & dosage
  • Calcitriol / blood*
  • Cattle / blood*
  • Female
  • Hydroxycholecalciferols / administration & dosage
  • Hydroxycholecalciferols / blood*
  • Injections, Intramuscular / veterinary


  • Hydroxycholecalciferols
  • 1,24,25-trihydroxyvitamin D3
  • 1,25,26-trihydroxyvitamin D3
  • Calcitriol