Expression of alternatively spliced variants of Na-Ca-exchanger-1 in experimental colitis: role in reduced colonic contractility.
Inflammation-induced colonic motility dysfunction is associated with a disturbance in Ca(2+) ion transporting mechanisms. The main objective of this study was to identify the types of Na-Ca-exchanger-1 (NCX-1) variants expressed in the rat colon, and how this was affected by colitis. In addition, the effect of colitis on the possible involvement of NCX-1 in the reduced carbachol-induced contraction of the rat colon was examined. Colitis was induced in male Sprague-Dawley rats by intra-rectal instillation of trinitrobenzenesulphonic acid (TNBS). Animals were killed on day 5. Colitis was characterized by estimating myeloperoxidase (MPO) activity, body weight, and histological scores. NCX-1 mRNA and protein variants were confirmed by RT-PCR coupled nucleotide sequencing and by Western blot analysis, respectively. Contractility of the colon segments was studied using standard procedure. There was a significant reduction in body weight of TNBS-treated rats. A significant increase in MPO activity and infiltration of inflammatory cells were observed in the inflamed rat colon. RT-PCR coupled nucleotide sequencing identified NCX-1.3 mRNA variant containing exons B and D. Western blot analysis confirmed 70 and 120 kDa molecular mass NCX-1 protein variants in rat colon. There was no significant difference (p > 0.05) in the level of NCX-1 protein variants in inflamed colon as compared to non-colitis controls. Functional experiments demonstrated that NCX in reverse mode played a role in carbachol-induced contraction of colon, and this was not affected by colitis. These findings demonstrated expression of a NCX-1.3 mRNA splice variant, and 70 and 118 kDa protein variants. Inhibition of the reverse mode of NCX-1 was not different in reduced carbachol-induced contraction between the groups. These findings are interpreted to suggest that NCX-1, though expressed did not play a role in reduced contractility in experimental colitis.
Department of Biochemistry, Faculty of Medicine, Kuwait University, Kuwait, Kuwait.
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Shubair
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Oriowo
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Khan
D017398:Alternative Splicing / Q000187:drug effects / Q000235:genetics*; D000818:Animals; D015153:Blotting, Western; D002217:Carbachol / Q000494:pharmacology; D003092:Colitis / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*; D003106:Colon / Q000187:drug effects / Q000473:pathology* / Q000503:physiopathology*; D005769:Gastrointestinal Motility / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019831:Sodium-Calcium Exchanger / Q000235:genetics*
D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D002217:Carbachol