Interrelationships between vitamin D3 and 25-Hydroxyvitamin D3 during chronic ethanol administration in the rat

Vitamin D {D} depleted female Sprague-Dawley rats were fed for a period of 4 wk a D deficient diet containing 36% of total calories as ethanol while control animals received an isocaloric regimen where ethanol was substituted for by dextrins. In conjunction with the ethanol feeding 92 I.U. of {¹⁴C}-vitamin D₃ {{¹⁴C}-D₃} were administered by intragastric gavage 3 times 1 wk for 3 $\text{2}\text{3}$ wk. At the end of the experiment, {¹⁴C}-D₃ and {¹⁴C}-25-hydroxyvitamin D₃ {{¹⁴C}-25(OH)D₃} concentrations were analyzed in plasma, liver, striated muscle and adipose tissue. Body reserves in unchanged {¹⁴C}-D₃ were significantly reduced by ethanol treatment as seen by 24%, 26%, and 59% lower plasma (p < 0.02), muscle (p < 0.001) and adipose tissue (p < 0.001) {¹⁴C}-D₃ concentrations in ethanol-treated compared to control rats. In contrast total plasma and liver {¹⁴C}-25(OH)D₃ content were increased by 30% (p < 0.05) and 55% (p < 0.001) respectively. This increased liver and plasma {¹⁴C}-25(OH)D₃ following ethanol treatment was not accompanied by a proportional {¹⁴C}-25(OH)D₃ incorporation into muscle and adipose tissue. These results suggest that during steady state conditions 25(OH)D₃ production is increased during chronic ethanol administration while the body pool in unchanged D₃ is significantly lowered. These results also point out that in the rat plasma 25(OH)D concentrations are not a reliable guide for the determination of vitamin D status during chronic ethanol administration.