CHARACTERISTICS OF ARTERIAL MYOSIN IN EXPERIMENTAL RENAL-HYPERTENSIONIN THE DOG

We compared myosin samples isolated from iliac-femoral arteries of con trol and renal (stenosis) hypertensive dogs to determine the effects o f increased blood pressure on the characteristics of the myosin. The r atio of 204-kd (SM-1) to 200 -kd (SM-2) myosin heavy chains was approx imately 1:0.75 for myosin from the iliac-femoral artery of normotensiv e dogs. This was not altered significantly in response to hypertension . Both SM-1 and SM-2 myosin heavy chains cross-reacted with antibody a gainst smooth muscle myosin on Western blot analysis. In addition to t hese heavy chains, purified myosin from both groups showed a very fain t protein band slightly below the 200 -kd myosin heavy chain on electr ophoresis on a highly porous sodium dodecyl sulfate-polyacrylamide gel . This protein band cross-reacted with antibody against nonmuscle myos in but not with smooth muscle myosin antibody. The 20- and 17-kd light chains of myosin isolated from normotensive and hypertensive dogs gav e similar results on isoelectric focusing. Peptide maps of tryptic dig ests of heavy chains revealed both quantitative and qualitative differ ences. The Ca2+-activated myosin ATPase activity measured in high salt (0.5 mol/L KCl) was similar for myosin from both groups, whereas the potassium (ethylenedinitrilo)tetraacetic acid-stimulated ATPase of myo sin from hypertensive animals was higher than that from normotensive a nimals. The actin-activated ATPase activities of the myosin from hyper tensive animals was also higher than that of the myosin isolated from normotensive artery (0.11 +/- 0.007 and 0.213 +/- 0.008 mumol P(i) per milligram per minute, respectively, for normotensive and hypertensive ). These studies indicate that the structural and functional propertie s of myosin in a muscular artery are altered in hypertensive dogs.