Induction of calbindin-D 9k mRNA but not calcium transport in rat intestine by 1,25-dihydroxyvitamin D3 24-homologs.
The function and precise mechanism of regulation of calbindin-D 9k in intestine is largely unknown. It is suggested that this calcium binding protein is involved in active intestinal calcium transport and that its expression is mainly mediated by 1,25-dihydroxyvitamin D3. We examined the effect of two side chain modified analogs of 1,25-dihydroxyvitamin D3 as compared to 1,25-dihydroxyvitamin D3 itself on the regulation of the calbindin-D 9k at the mRNA level and on intestinal calcium transport in the rat. delta 22-24,24-dihomo-1,25-dihydroxyvitamin D3 at a single dose of 500, 1,000, and 2,000 pmol caused greater than 7.0-fold increase in calbindin-D 9k mRNA without stimulating intestinal calcium transport. A 10,000-pmol dose of delta 22-24,24,24-trihomo-1,25-dihydroxyvitamin D3 caused a 7.6-fold increase in calbindin-D 9k mRNA without significantly increasing intestinal absorption of calcium. In contrast, 1,25-dihydroxyvitamin D3 caused a parallel increase in calbindin-D 9k mRNA and intestinal absorption of calcium. Thus, calbindin 9k is not by itself responsible for 1,25-dihydroxyvitamin D3-mediated increase in intestinal absorption of calcium.
Krisinger
J
J
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.
Strom
M
M
Darwish
H D
HD
Perlman
K
K
Smith
C
C
DeLuca
H F
HF
D000818:Animals; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000097:blood; D007408:Intestinal Absorption; D007422:Intestines / Q000502:physiology*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis* / Q000235:genetics; D013329:Structure-Activity Relationship; D013997:Time Factors
D064026:Calbindins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D002117:Calcitriol; D002118:Calcium