Effect of sunlight exposure on circulating 1,25-dihydroxyvitamin D in hemodialyzed patients and of exogenous parathyroid hormone in anephric patients.
Sunshine exposure increased the serum concentration of 25-hydroxyvitamin D (25-OHD) in 9 hemodialyzed patients. Mean 1,25-dihydroxyvitamin D (1,25-(OH)2D) was unchanged, but in two patients with low initial 25-OHD values this increase was accompanied by a rise in circulating 1,25-(OH)2D, although not to normal levels. One hemodialyzed patient developed liver insufficiency with a resultant reduction of serum 25-OHD concentration accompanied by a decrease in serum 1,25-(OH)2D concentration. The results indicate that the circulating levels of 1,25-(OH)2D in patients with end-stage renal failure are to some extent regulated by the serum 25-OHD concentrations. Injection of parathyroid hormone (PTH) induced minor increases in serum concentrations of 1,25-(OH)2D in patients with end-stage renal failure and even in anephric patients, suggesting the existence of an extrarenal PTH-sensitive 1-alpha-hydroxylase. However, the enzyme was stimulated by supraphysiological concentrations of PTH, and therefore not necessarily of importance in the normal regulation of calcium metabolism.
D015650:24,25-Dihydroxyvitamin D 3; D000328:Adult; D004100:Dihydroxycholecalciferols / Q000378:metabolism*; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000378:metabolism; D007275:Injections, Intravenous; D007674:Kidney Diseases / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009392:Nephrectomy; D010281:Parathyroid Hormone / Q000008:administration & dosage*; D006435:Renal Dialysis; D013472:Sunlight
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010281:Parathyroid Hormone; D015650:24,25-Dihydroxyvitamin D 3; D006899:Mixed Function Oxygenases