Abstract
The biochemical, nutritional chemical and comparative biochemical studies on vitamin D were performed and the following results have been obtained. 1. Physiological activities of two kinds of novel vitamin D_3 derivatives, 22-oxa-1α,25(OH)_2D_3(OCT) and 2β-(3-hydroxy-propoxy)-1α,25(OH)_2D_3 (ED-71) have been studied. OCT, which has less calcemic and stronger cell differentiation activities than 1α,25(OH)_2D_3 was clarified to have the properties of weak binding affinity for vitamin D binding protein (DBP), rapid turn-over in the body and rapid excretion into bile. On the other hand, ED-71, which has stronger effects on intestinal calcium absorption and longer bone turn-over than 1α,25(OH)_2D_3 was clarified to have the properties of stronger binding affinity for DBP and longer half-life in blood than 1α,25(OH)_2D_3. 2. Assay of vitamin D in various kinds of Japanese foods revealed that fish generally contained high levels of vitamin D. 3. Assay of vitamin D and its metabolites in milk revealed that neither mother milk nor cow's milk contained enough amounts of vitamin D and its derivatives. 4. The origin of extremely high contents of vitamin D_3 in fish liver was confirmed to be a result of food chains originated from plankton. 5. The existence of 25-OH-D_3-1α-hydroxylase in the liver of fish was found. 6. Comparative studies on vitamin D metabolism in the liver and kidney of vertebrates (fish, amphibians, reptile and mammals) and fetal and mature rats support the thesis that ontogeny is a recapitulation of phylogeny.
