The effect of induced metabolic acidosis on vitamin D3 metabolism in rachitic chicks

Summary The metabolism of vitamin D₃ was studied in 3-week-old, vitamin D deficient chicks, fed since hatching with a diet containing 3% ammonium chloride, 1% calcium, and 0.7% phosphorus. When kidney homogenates were incubated in vitro with ³H]25-(OH)D₃, the production of 1,25-(OH)₂D₃ was reduced by 40% in acidotic birds. During in vivo experiments, after injection of ³H]D₃ (1220 pM/bird), the level of 1,25-(OH)₂D₃ was also reduced in blood plasma, intestine, and tibiae in acidotic chicks as compared with the controls. As a large increase in plasma phosphate was found during acidosis, these results are discussed in relation to the possible role of phosphorus in the control of 1,25-(OH)₂D₃ synthesis.