Different ratio of myosin heavy chain isoforms in arterial smooth muscle of spontaneously hypertensive rats

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Abstract
The relative proportion of the two putative heavy chains of smooth muscle myosin (MHC1 and MHC2) was determined in the caudal and femoral arteries of spontaneously hypertensive rats (SHR) and normotensive (WKY) rats at 16 weeks of age. The heavy chain polypeptides with Mr 204000 and 200000 were resolved electrophoretically under denaturing conditions in porous polyacrylamide gels. Both proteins reacted strongly with a monoclonal antibody (2C4) to smooth muscle MHC. In caudal arteries the ratio of MHC1/MHC2 was 3.1∶1 in SHR rats compared with 1.8∶1 in WKY rats (p<0.005) and similarly in femoral arteries, 2.8∶1 vs 1.5∶1 (p<0.001). In the portal vein there was no significant difference, 1.7∶1 vs 1.5∶1. The possibility that the higher MHC ratio in the SHR is the genetically mediated defect in arterial smooth muscle cells leading to the hypertension is discussed as an alternative to the elevated systemic blood pressure causing the altered MHC ratio.