We evaluated the turnover of the plasma 25-OH-vitamin D pool, acid, and mineral balances in paired balance studies of 6 normal subjects during normal acid base conditions and during stable chronic metabolic acidosis induced by NH4C1. Positive acid balances and negative Ca balances due to hypercalciuria were observed as previously reported. Plasma 25-OH-D pool turnover averaged 6.1 ± 0.4 nmol/day during control and did not change during acidosis (6.5 ± 0.5 nmol/day) nor were any significant increments in net intestinal absorption of Ca, PO4, or Mg, the physiological expression of vitamin D action, observed during acidosis. In 3 other subjects, repetitive measurements of serum iPTH during 7 control days and 24 days of stable NH4C1 acidosis showed no changes. We interpret the data to support the hypothesis that neither PTH nor vitamin D and its metabolites mediates the increase in net bone resorption that must accompany chronic metabolic acidosis.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical