The effect of vitamin D on urinary citrate in relation to calcium, phosphorus and urinary pH

Vitamin D increased the amount of urinary citrate excreted by young rats kept on rations varying widely in mineral content. These rations ranged in composition from those providing an adequate mineral intake to those made grossly deficient in Ca, P, and other minerals. The biggest percentage increase in citrate was obtained with P-containing rations, but supplements of P, given in the form of neutral solutions of K phosphates to a low-P ration, reduced citrate elimination. An increase in urinary pH induced by vitamin D with rats on low-P rachitogenic rations was not obtained with rations adequate in P, yet an increase in citrate elimination resulted in all instances. Inasmuch as a supplement of vitamin D increased urinary citrate far more than did an additional large intake of NaHCO 3, it appears that the effect of vitamin D is due to an increase in citrate synthesis rather than to a decrease in its destruction.