Table 9.
Status of β1-adrenreceptors and adenylyl cyclase activity in the presence of isoproterenol (100 μM) in the right ventricle from the control as well as different stages of heart failure at 4, 8 and 16 weeks of myocardial infarction (MI) in rats.
| Parameters | Control | Early Failure Stage (4 Week MI) |
Moderate Failure Stage (8 Weeks MI) |
Severe Failure Stage (16 Weeks MI) |
|---|---|---|---|---|
| A. β1-Adrenoreceptors | ||||
| Bmax (f mol/mg protein): | 24 ± 2.3 | 29 ± 3.1 | 28 ± 3.1 | 27 ± 3.2 |
| Kd (pM): | 48 ± 3.3 | 49 ± 3.4 | 49 ± 4.0 | 49 ± 4.1 |
| B. β2-Adrenoreceptors | ||||
| Bmax (f mol/mg protein): | 8 ± 1.9 | 7 ± 1.1 | 9 ± 2.0 | 10 ± 1.8 |
| Kd (pM): | 13 ± 1.2 | 14 ± 1.0 | 11 ± 1.3 | 12 ± 1.4 |
| C. Adenylyl cyclase activity (pmol cyclic AMP/10 min/mg protein) | ||||
| Isoproterenol | 402 ± 35 | 258 ± 21 * | 640 ± 42 * | 648 ± 45 * |
Values are mean ± SE of four to six animals. Both maximal binding (Bmax) and dissociation constants (Kd) were calculated from the Scatchard plot analysis. (125I) iodocyanopindolol binding was obtained by employing CGP-20712A for β1-adrenoreceptors and ICI-118551 for β2-adrenoreceptors. Determination of adenylyl cyclase in the presence of isoproterenol was carried out by using 10 μM Gpp(NH)p in the assay medium. The data are based on information in our paper, Sethi et al., 1997 [46]. * p < 0.05 vs respective control.