Synthesis and biological activity of vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate: role of vitamin D2 conjugates in calcium homeostasis.
To ascertain the physiologic function of vitamin D2 conjugates in calcium homeostasis, we synthesized vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate in pure form and tested their biological activity in vitamin D deficient rats fed a low calcium diet. Vitamin D2 3 beta-glucosiduronate was active in promoting calcium transport in the intestine at a dose of 100 pmol per rat. It increased calcium mobilization from bone and soft tissue at a dose of 1000 pmol per rat. This conjugate was less active than equimolar doses of vitamin D2. These results demonstrate that vitamin D2 3 beta-glucosiduronate can be utilized by the rat as a source of vitamin D. In contrast, vitamin D2 3 beta-sulfate was biologically inert. It failed to increase calcium transport in the duodenum of vitamin D deficient rats except at the highest doses tested (greater than 100,000 pmol/rat). It was similarly ineffective in increasing calcium mobilization from bone and soft tissue. Our results lead us to conclude that vitamin D2 3 beta-glucosiduronate is probably utilized by the rat after hydrolysis to the free sterol; on the contrary, the sulfate is not biologically active except at the highest doses tested.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004872:Ergocalciferols / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D006706:Homeostasis / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051381:Rats; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D004872:Ergocalciferols; C036282:vitamin D2 sulfate; C036286:vitamin D2 glucosiduronate; D002118:Calcium