A physiological basis for variation in the contractile properties of isolated rat heart

摘要: 1. The maximum Ca(2+)-activated force, velocity of unloaded shortening and both Ca(2+)- actin-activated ATPase activities myosin have been measured in detergent-skinned preparations isolated bundles rat right ventricle after exposure the intact tissue to different conditions superfusion, mechanical activity temperature. 2. Maximum force per unit cross-sectional area decreases with increasing area, and, absence electrical stimulation, duration superfusion. is not influenced by these differences. 3. Actin-activated as increases superfusion increases, but extent decrease enzymatic less than that developed force. independent 4. cryostatic sections quickly frozen uniform across transverse section. In thin bundles, it highest centre lowest at edge section, which correspond, respectively, surface bundle. Exposure section 1 microM-cyclic AMP largest increase occurring or near 5. changed cyclic AMP. 6. Electrical elevated Ca2+ concentration medium, isoprenaline partially completely reverse decline produced prolonged bundle before its skinning. 7. These observations are similar many ways those made on frog skeletal muscles Elzinga, Howarth, Rull, Wilson & Woledge (1989a). An explanation based existence a physiological mechanism for regulating properties generators proposed. Regulation attachment cross-bridge an actin filament may be basis regulatory mechanism.