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Chronic hypoxia promotes preferential loss of MLCK not associated with MLC in fetal lamb arteries (700.7)
Author(s) -
Williams James,
Aguilar Luisa,
Pearce William
Publication year - 2014
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.28.1_supplement.700.7
Subject(s) - myosin light chain kinase , contractility , anatomy , myosin , chemistry , biology , medicine , microbiology and biotechnology , endocrinology
As we have previously shown (PMID: 23325408), chronic hypoxia (CH) dramatically reduces MLCK abundance in fetal common carotid arteries without proportionate loss of contractility. The present study explores the hypothesis that CH preferentially decreases MLCK not associated with MLC and thereby preserves contractility. Common carotid arteries from term fetal sheep were mounted in a custom‐made organ bath apparatus that enabled computer controlled freezing of artery samples in 200 msec increments (PMID: 18835918). Artery segments were frozen in methacarn fixative and analyzed for MLC, S19 pMLC and MLCK by Westerns and confocal microscopy. CH reduced MLCK abundance 24‐fold, but did not significantly alter MLC abundance. Despite decreased MLCK abundance, rates of ser19 MLC phosphorylation after 1 sec electrical stimulation were unchanged in Calyculin A (10 nM) pre‐treated arteries (27.6±0.8% N, 22.4±4.9% H). Confocal microscopy revealed that colocalization of MLC with MLCK was increased more than 3‐fold in hypoxic arteries. These data indicate that hypoxic losses of MLCK are restricted to a fraction of MLCK not associated with MLC, such that the remaining MLCK is more tightly colocalized with MLC and is fully capable of phosphorylating MLC and sustaining contraction. The role of the large fraction of MLCK not colocalized with MLC is unclear, but may serve structural or other non‐enzymatic purposes. Grant Funding Source : Supported by NIH Grants HD‐31266 and NS‐076945