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Acquired alterations in vitamin D metabolism in the acidotic state
Insights
Metabolic acidosis in chicks affects vitamin D metabolism. This study shows that acidosis alters the production and breakdown of 1,25-dihydroxyvitamin D3, impacting calcium levels and growth.
Area of Science:
- Biochemistry
- Pediatric Endocrinology
- Nutritional Science
Background:
- Classic (Type I) renal tubular acidosis in children presents with growth retardation and rickets.
- Alkali therapy can correct these abnormalities.
- The chick model is used to study vitamin D metabolism in acidosis.
Purpose of the Study:
- To investigate the effects of metabolic acidosis on vitamin D metabolism.
- To understand how acidosis influences the production and degradation of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3).
Main Methods:
- Rachitic chicks were treated with ammonium chloride (NH4Cl) for 96 hours.
- Serum calcium levels and blood pH were measured.
- The metabolism of radiolabeled 25-hydroxyvitamin D3 ([3H]25OHD D3) and 1,25-dihydroxyvitamin D3 ([3H]1,25(OH)2D3) was assessed.
Main Results:
- NH4Cl ingestion led to increased serum calcium and decreased blood pH.
- A reduction in [3H]1,25(OH)2D3 levels was observed after [3H]25OHD D3 injections.
- Enhanced metabolic clearance of administered [3H]1,25(OH)2D3 was noted.
Conclusions:
- Metabolic acidosis in chicks alters the production of 1,25-dihydroxyvitamin D3.
- Metabolic acidosis also affects the degradation rate of 1,25-dihydroxyvitamin D3.
- These alterations in vitamin D metabolism may contribute to the observed abnormalities in acidotic states.
Abstract:
Classic (type I) renal tubular acidosis in children in attended by growth retardation and rickets, abnormalities that can be corrected by alkali therapy alone. We have employed the NH4Cl-treated rachitic chick as a model to investigate vitamin D metabolism in the acidotic state. NH4Cl ingestion for 96 h was associated with a rise in serum calcium, a significant decrease in blood pH (7.42 +/- 0.08 vs 7.30 +/- 0.08, P less than 0.005), decreased [3H]1,25(OH)2D3 following [3H]25OHD D3 injections, and enhanced metabolic clearance of administered [3H]1,25(OH)2D3. The data collectively suggest that metabolic acidosis in the chick alters the production and degradation of 1,25(OH)2D3.