Decreased contractile responses to isoproterenol in isolated cardiac myocytes from ageing guinea-pigs

We have characterized the age-related changes of contractility and β-adrenoceptor function in isolated cardiac myocytes from guinea-pigs. We used either adult animals from 2 to 14 weeks of age, where body weight increases linearly with age, or senescent ones aged between 53–65 weeks. There was some indication of a decrease in contractility in maximum Ca 2+ with age, with significant differences between a young (≤4 weeks, weight 600 g) group in contraction amplitude expressed as percentage shortening (but not when expressed as μm change in length) or contraction and relaxation velocities. This decline was continued into senescence, and ANOVA showed a significant difference between the three groups for contraction amplitude (percentage shortening, 12.2 ± 0.9%, young, n = 31; 9.5 ± 0.6%, n = 28 aged; 6.7 ± 0.8%, n = 6, senescent; P = 0.005), and contraction or relaxation velocities ( P