Expression of the novel epithelial Ca2+ channel ECaC1 in rat pancreatic islets.
The epithelial Ca2+ channel, ECaC1, is primarily expressed in the apical membrane of vitamin D-responsive tissues. This study characterizes for the first time the presence of this novel channel in pancreatic tissue by reverse transcriptase-polymerase chain reaction and immunohistochemistry. In addition, the expression of ECaC1 was investigated in an animal model for Type 2 diabetes mellitus, the Zucker diabetic fatty (ZDF) rat. Identical staining patterns for ECaC1 and insulin were observed, whereas no co-localization of ECaC1 with glucagon was found. ECaC1, insulin, and prohormone convertase 1 (a neuroendocrine endoprotease expressed in secretory granules) showed a similar punctate staining. ECaC1 co-localized with the Ca2+ binding protein calbindin-D(28K) in the beta-cells. Furthermore, in contrast to wild-type rats, in ZDF rats aging led to a progressive decrease in both insulin and ECaC1 staining. Plasma 1,25-dihydroxyvitamin D3 levels were similar in both control and ZDF rats and decreased with aging. Taken together, our findings indicate that this novel Ca2+ channel may play a role in the regulation of endocrine Ca2+ homeostasis.
Janssen
Susan W J
SW
Department of Animal Physiology, Faculty of Science, University of Nijmegen, Nijmegen, The Netherlands.
Hoenderop
Joost G J
JG
Hermus
Ad R M M
AR
Sweep
Fred C G J
FC
Martens
Gerard J M
GJ
Bindels
René J M
RJ
D000818:Animals; D002117:Calcitriol / Q000097:blood; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007515:Islets of Langerhans / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011924:Rats, Zucker; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels
D015220:Calcium Channels; D012333:RNA, Messenger; D050916:TRPV Cation Channels; C492241:TRPV5 protein, rat; D002117:Calcitriol