Stretch-induced phosphorylation of the 20,000-dalton light chain of myosin in arterial smooth muscle.
Stretching to 1.7 times the resting length of porcine carotid arteries reversibly prevents active tension development by K+ or norepinephrine stimulation. The 20,000-dalton light chain of myosin was maximally phosphorylated in the stretched noncontracting muscles, equal to that in the nonstretched contracting muscles challenged with K+ or norepinephrine. These results show that the contractile event is not a prerequisite for phosphorylation. Furthermore, stretching alone also induced maximal light chain phosphorylation even in the absence of K+ or norepinephrine. The stretch-induced light chain phosphorylation was not affected by exhaustive washing of the muscle with Ca2+-free physiological salt solution, treatment of the muscle with verapamil, or by a short exposure to ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). Prolonged EGTA treatment abolished the stretch-induced light chain phosphorylation. All evidence suggests that upon stretch, Ca2+ is released from intracellular sources and this Ca2+ activates the myosin light chain kinase producing phosphorylation of the light chain.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002339:Carotid Arteries / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D013552:Swine
D004533:Egtazic Acid; D009218:Myosins; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine