| Popis: |
This chapter discusses various biochemical aspects of vitamin D metabolism in man. Inositol polyphosphates derived from the partial hydrolysis of phytic acid can inhibit the calcification in vitro of ricketic rat cartilage and rat aorta-injected parentally, they will protect the aorta from the calcification induced by vitamin D intoxication. In preliminary experiments, it appears that injected inositol phosphates may also partly prevent the curative effects of physiological amounts of vitamin D in rats with low phosphate rickets, although they are less potent in this respect than the synthetic diphosphonates. The implications of an excessive intake are best seen in caricature by observing the disposition of pharmacological doses of the vitamin. Patients with advanced renal or without kidneys also have a normal capacity to form 25-hydroxycholecalciferol, but this metabolite, while more effective than an equivalent dose of cholecalciferol in treating renal osteodystrophy, is only effective in pharmacological and not in physiological dosage. |
