Relationship of vitamin D with calbindin D9k and D28k expression in ameloblasts.
OBJECTIVE
Calbindin D9k (CB9k) and D28k (CB28k) are intracellular soluble calcium-binding proteins, whose expressions are considered to be regulated by vitamin D. However, the amount of CB28k expression in the kidneys of vitamin D receptor-null mice was reported to be similar to that in wild type mice, suggesting no dependence on vitamin D for its expression in kidneys. In the present study, we evaluated the effects of vitamin D on the expressions of CB9k and CB28k during amelogenesis.


METHODS
Rats fed a vitamin D-deficient diet (VD(-) rats) or a standard diet (VD(+) rats) were subjected to immunohistochemical assays using anti-CB9k and anti-CB28k anti-serum. Further, after culturing in medium containing 1,25(OH)(2)D(3) at various doses, quantitative RT-PCR analyses of CB9k and CB28k mRNA were performed using tooth germs from the lower first molars of ICR mice.


RESULTS
CB9k-immunoreactivity was detected faintly during the secretory stage of ameloblasts in the incisors of VD(+) rats, with increased staining observed during the maturation stage, whereas no such immunoreactivity was detected in those of VD(-) rats. In contrast, the distribution of CB28k in the teeth of VD(-) rats was nearly identical to that in teeth of VD(+) rats, with immunoreactivity detected in both secretory and maturation ameloblasts. Further, quantitative RT-PCR analyses revealed that the amount of CB9k mRNA was increased in a dose-dependent manner, whereas that of CB28k mRNA was not changed.


CONCLUSIONS
Vitamin D has no effect on the expression of CB28k, whereas it has a significant effect on that of CB9k in ameloblasts.
Onishi
Tomoyuki
T
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan. onishi@dent.osaka-u.ac.jp
Shintani
Seikou
S
Wakisaka
Satoshi
S
Ooshima
Takashi
T
D000565:Ameloblasts / Q000378:metabolism*; D000818:Animals; D064026:Calbindins; D007150:Immunohistochemistry; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018167:Receptors, Calcitriol / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism*; D014083:Tooth Germ / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000378:metabolism*
D064026:Calbindins; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D064030:S100 Calcium Binding Protein G; C576507:S100g protein, mouse; C576508:S100g protein, rat