Length‐Dependent Regulation of ROK Activity During KCl‐Induced Tonic Force in Rabbit Epigastric Artery Involves Microtubule Depolymerization

TL;DRAbstract

Vascular smooth muscle contraction can be divided temporally into early (phasic) and late (tonic) phases. ROK regulates tonic force by phosphorylating the regulatory subunit of myosin light chain (MLC20) phosphatase (MLCP), MYPT1. Whether alterations in muscle length can regulate ROK activity has yet to be determined. Epigastric Artery (EA) showed increasing tonic-to-peak force ratios with increasing circumferential (length) stretch of the vessel, indicating that the degree of tonic force was selectively muscle length-dependent. The ROK inhibitor, Y-27632, completely abolished tonic force at all lengths examined. Femoral artery (FA) showed no significant differences in basal and KCl-stimulated MLC20 -p and MYPT-p levels when comparing muscles at slack length (Ls) to those preloaded by stretching to 1.2-fold the optimal length for muscle contraction (Lp). This is in contrast to EA, in which an increase in muscle stretch from Ls to Lp caused increased basal levels of MLC20-p (Ls: 9.40±1.

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