cholecalciferol and Acidosis

Homeostasis of inorganic phosphate (P(i)) is primarily an affair of the kidneys. Reabsorption of the bulk of filtered P(i) occurs along the renal proximal tubule and is initiated by apically localized Na(+)-dependent P(i) cotransporters. Tubular P(i) reabsorption and therefore renal excretion of P(i) is controlled by a number of hormones, including phosphatonins, and metabolic factors. In most cases, regulation of P(i) reabsorption is achieved by changing the apical abundance of Na(+)/Pi cotransporters. The regulatory mechanisms involve various signaling pathways and a number of proteins that interact with Na(+)/P(i) cotransporters.

Topics: Acidosis; Animals; Cholecalciferol; Circadian Rhythm; Diet; Fibroblast Growth Factor-23; Fibroblast Growth Factors; Gene Expression Regulation; Glucuronidase; Gonadal Steroid Hormones; Homeostasis; Humans; Ion Transport; Kidney Tubules, Proximal; Klotho Proteins; Parathyroid Hormone; Phosphates; Phosphoproteins; Potassium Deficiency; Signal Transduction; Sodium-Hydrogen Exchangers; Sodium-Phosphate Cotransporter Proteins; Sodium-Phosphate Cotransporter Proteins, Type IIa; Sodium-Phosphate Cotransporter Proteins, Type IIc

Studies in rats with renal ablation indicate that anemia lessens, whereas its vigorous correction with recombinant human erythropoietin (r-HuEPO) worsens systemic and glomerular hypertension, factors known to promote progression of chronic renal failure (CRF). However, in human studies, use of r-HuEPO in predialysis patients has not been associated with worsening renal function, provided blood pressure control is achieved. Histological evidence of bone disease is common in early renal failure, and deficits in calcitriol synthesis seem to be an important factor in the pathogenesis of secondary hyperparathyroidism (HPTH) in early CRF. Reports to data, on the use of low dose active vitamin D metabolites in predialysis patients, indicate either a reversible decline or no decline in renal function. Adynamic bone disease, however, may ensure during such therapy if excessive reductions in serum intact parathyroid hormone concentrations occur. Recent data suggest that chronic metabolic acidosis decreases albumin synthesis, increases muscle proteolysis, and induces negative nitrogen balance in patients with CRF. Despite these experimental data, the clinical relevance of correction of metabolic acidosis in end-stage renal disease (ESRD) is still not defined. Even though therapy of metabolic acidosis in the adult patient with CRF remains conjectural at this time, reports indicate that its correction might lead to healing of osteomalacia and osteopenia, and possibly may decrease protein degradation and improve growth in children with CRF.

Topics: Acidosis; Adult; Anemia; Animals; Calcitriol; Calcium Compounds; Cholecalciferol; Chronic Kidney Disease-Mineral and Bone Disorder; Ergocalciferols; Erythropoietin; Humans; Kidney Failure, Chronic; Rats; Recombinant Proteins; Renal Dialysis

Topics: Acidosis; Calcitriol; Cholecalciferol; Energy Metabolism; Follow-Up Studies; Humans; Urinary Reservoirs, Continent

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.

Topics: Acidosis; Ammonium Chloride; Animals; Chickens; Cholecalciferol; Diet; Dihydroxycholecalciferols; Hydroxycholecalciferols; Intestine, Small; Kidney; Liver; Rickets; Tibia

Topics: Acidosis; Animals; Calcium; Cattle; Cattle Diseases; Cholecalciferol; Female; Magnesium; Paralysis; Phosphorus; Pregnancy; Puerperal Disorders

Topics: Acidosis; Alkaline Phosphatase; Animals; Bone and Bones; Bone Development; Bone Resorption; Calcitonin; Calcium; Cholecalciferol; Chromium Isotopes; Citrates; Cortisone; Dogs; Hydrochloric Acid; Hydrogen-Ion Concentration; Hypercalcemia; Hypocalcemia; Metatarsus; Microradiography; Osteoclasts; Parathyroid Hormone; Perfusion; Phosphates; Phosphorus; Thyroxine