Differential responses of canine myosin ATPase activity and tissue gases in the pressure-overloaded ventricle dependent upon degree of obstruction: mild versus severe pulmonic and aortic stenosis.
Mild pulmonic stenosis, induced in dogs by banding the pulmonary artery, elevated right ventricular peak systolic pressure to 60% above the control and elevated right ventricular K+- and Ca2+- activated myosin ATPase activities. In contrast, severe pulmonic stenosis, which elevated right ventricular peak systolic pressure to 300% above the control, did not produce an increase in myosin enzymatic ATPase Vmax values but caused a decrease in myosin activity. Mild aortic stenosis, induced by banding the ascending aorta, forcing a transaortic pressure gradient of 25 mm Hg, caused an elevation in left ventricular muosin ATPase, whereas severe aortic banding, brought about by creating a transaortic pressure gradient of 55 mm Hg, never caused an elevation in left ventricular myosin enzymatic Vmax values, but, like severe pulmonic banding, caused a decrease in K+- and Ca2+- activated myosin activities. Normal left ventricular myosin Vmax values in mumol of PO4/mg-min at 37 degrees C were: K+ = 2.84 +/- 0.22, and Ca2+ = 0.97 +/- 0.14. For right ventricular myosin they were: K+ = 2.15 +/- 0.16, and Ca2+ =0.74 +/- 0.10. Analyses of tissue gases, based on mass spectrometry data, showed that the hypertrophied ventricles had an elevated tissue pCO2 and an elevation in the cGMP/cAMP ratio.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001020:Aortic Stenosis, Subvalvular / Q000378:metabolism* / Q000503:physiopathology; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002312:Cardiomyopathy, Hypertrophic / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004285:Dogs; D006352:Heart Ventricles / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011662:Pulmonary Subvalvular Stenosis / Q000378:metabolism* / Q000503:physiopathology; D013312:Stress, Physiological / Q000503:physiopathology
D002245:Carbon Dioxide; D000242:Cyclic AMP; D000251:Adenosine Triphosphatases; D009218:Myosins; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium