[Effect of ascorbic acid on 25-hydroxyvitamin D3 metabolism in the kidneys and 1,25-dihydroxyvitamin D3 reception in the small intestine mucosa of guinea pigs].
Ascorbic acid deficiency in vitamin D-supplied guinea pigs caused a moderate decrease of Ca in the blood and osseous tissue, a 1.5-fold decrease of 2.5-hydroxyvitamin D (25-OH D) in blood serum, a 2-fold decrease of the 25-OH D 1-hydroxylase activity in kidneys and a 1.6-fold increase of the 24-hydroxylase activity. The concentration of 1.25-dihydroxyvitamin D3 (1.25-(OH)2D3) nuclear receptors in small intestinal mucosa diminished by 20-30%; in this case the percentage of occupied hormone receptors reduced from 11.8 to 8.6%. The affinity of receptors for 1.25-(OH)2D3 did not change thereby (Kd = 0.25-0.26 nM; Kd2 = 0.06-0.10 nM). At the same time the value of cooperativity coefficient showed a decrease-from 1.7 to 1.4, which was accompanied by a reduction of the maximum capacity of receptors (1.2-1.5-fold). Vitamin C depletion augmented the manifestation of vitamin D deficiency in guinea pigs and impeded their correction after administration of cholecalciferol. This markedly retarded the restoration of the 25-OH D level in the blood as well as the number of occupied and unoccupied nuclear receptors for 1.25-(OH)2D3. The experimental results illustrate the effects of ascorbic acid on the vitamin D hormonal system function, which is manifested both at the level of 1.25-(OH)2D3 synthesis in the kidneys and of its receptor binding in target tissues.
Sergeev
I N
IN
Arkhapchev
Iu P
IuP
Kim
R K
RK
Kodentsova
V M
VM
Spirichev
V B
VB
D000818:Animals; D001206:Ascorbic Acid Deficiency / Q000378:metabolism*; D001842:Bone and Bones / Q000378:metabolism; D002112:Calcifediol / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D006168:Guinea Pigs; D007413:Intestinal Mucosa / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000378:metabolism
D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002112:Calcifediol; D002118:Calcium
Vliianie askorbinovoĭ kisloty na obmen 25-oksivitamina D3 v pochkakh i retseptsiiu 1,25-dioksivitamina D3 v slizistoĭ obolochke tonkogo kishechnika u morskikh svinok.