Vitamin D-independent expression of chick brain calbindin-D28K.
A combination of calbindin-D28K-specific cDNA probes and polyclonal antisera were used to investigate expression of the calbindin-D28K in the vitamin D-deficient avian brain in vivo in response to pharmacological doses of the vitamin D3 metabolite, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Serum calcium levels were stimulated (2-fold) and intestinal calbindin-D28K expression (between 10- and 30-fold) by 1,25(OH)2D3 (6.5 nmol/animal) after 12 h. In marked contrast, steady-state whole brain levels of calbindin-D28K as judged by enzyme-linked immunoassay (ELISA) remained constant. Northern gel analysis revealed that three species of calbindin-D28K mRNA (2.0, 2.6 and 3.1 kb) were present a priori in the vitamin D-deficient chick brain and that administration of pharmacological doses (6.5 nmol/animal) of 1,25(OH)2D3 failed to influence their relative abundance. Separate but parallel dot blot hybridization analyses also confirmed that brain calbindin-D28K-mRNA levels were not influenced by 1,25(OH)2D3. These experiments demonstrate at the molecular level that, in contrast to the intestine, the gene encoding calbindin-D28K in the brain is regulated by mechanism(s) or factors which are independent of vitamin D status.
Hall
A K
AK
Division of Biomedical Sciences, University of California, Riverside 92521.
Norman
A W
AW
D000818:Animals; D001812:Blood-Brain Barrier; D001923:Brain Chemistry / Q000187:drug effects; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002645:Chickens; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation; D012333:RNA, Messenger / Q000032:analysis; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis* / Q000235:genetics; D014808:Vitamin D Deficiency / Q000378:metabolism*
D064026:Calbindins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D004247:DNA; D002117:Calcitriol; D002118:Calcium