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Ca2+ sensitization contributes to basal contractions of smooth muscles from different regions of a murine gastrointestinal tract
Author(s) -
Bhetwal Bhupal P,
Perrino Brian A
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1115.28
Subject(s) - rho associated protein kinase , biology , myosin light chain kinase , gq alpha subunit , medicine , myosin light chain phosphatase , endocrinology , muscle contraction , nicardipine , antrum , myosin , anatomy , microbiology and biotechnology , phosphorylation , signal transduction , biochemistry , stomach , g protein , blood pressure
Ca2+ sensitization of smooth muscle contraction occurs by myosin light chain phosphatase (MLCP) inhibition. CPI‐17 phosphorylation or MYPT‐1 phosphorylation by Rho kinase inhibits MLCP. We employed western blotting to examine the levels of proteins involved in Ca2+ sensitization to address a question; is basal Ca2+ sensitization different among smooth muscles from antrum, fundus and proximal colon (PC) in a murine gastrointestinal (GI) tract? Fundus and PC smooth muscles showed higher levels of Ca2+ sensitization proteins than antrum. Myosin light chain (MLC) and pSer19‐MLC levels were lower in fundus and PC compared to that in antrum. Rho kinase inhibitorY‐27632, reduced contractions and MYPT‐1 pThr853 levels, perhaps with different sensitivities, in all three smooth muscles. Y‐27632 reduced MYPT‐1 pThr696 levels in fundus, but not in antrum and PC smooth muscles. L‐type Ca2+ channel blocker, nicardipine, reduced antrum and PC smooth muscle contractions without affecting MYPT‐1 pThr853 or pThr696 levels. Whereas, nicardipine did not affect fundus smooth muscle contraction but still reduced MYPT‐1 phosphorylation. pSer19‐MLC levels were reduced by Y‐27632 or nicardipine in fundus and PC, but not in antrum smooth muscles. These findings suggest that both Ca2+ dependent mechanisms and MLCP inhibition by MYPT‐1 phosphorylation contribute to basal contractile properties of GI smooth muscles. Supported by NIH Grant RR018751.