Aims: 

There are conflicting results dealing with effect of proadrenomedullin N-terminal 20 peptide (PAMP) on coronary perfusion pressure (PP), contractile force (CF) and heart rate (HR). Little is known about effect of calcitonin on PP, CF and HR. Furthermore, action of human and rat PAMP as well as salmon and rat calcitonin has not been compared. Therefore, we have studied possible effect of these peptides on PP, left ventricular developed pressure (LVP) as an index of CF and HR in isolated rat hearts.

Methods: 

The hearts were perfused with modified Krebs-Henseleit solution under constant flow (12 ml/min) condition. Rat PAMP, human PAMP, rat calcitonin and salmon calcitonin were infused to separate groups of hearts.

Results: 

Rat PAMP (n = 7) did not affect PP. However, it increased HR (at 10^-9 M from 257.83 ± 9.55 to 282 ± 9.98 beats/min, mean±SE, p < 0.05 at 10^-8 M from 259.83 ± 10.02 to 289.83 ± 7.8 beats/min, p < 0.001 and at 10^-7 M from 249.66 ± 7.67 to 280.5 ± 10.1 beats/min, p < 0.001). Rat PAMP at a dose of 10^-9, 10^-8 and 10^-7 M decreased LVP from 90.5 ± 7.39 to 78.66 ± 5.08 mmHg, (p < 0.01), from 88 ± 4.04 to 73 ± 4.95 mmHg (p < 0.01) and from 79.83 ± 3.59 to 64.83 ± 4.05 (p < 0.001), respectively. Rat calcitonin (n = 7) did not alter PP and slightly decreased LVP. The peptide at a dose of 10^-8 M also slightly decreased HR. Rat calcitonin at 10^-7 and 10^-6 M concentrations significantly decreased HR from 263.83 ± 10.93 to 247 ± 14.57 beats/min (p < 0.01) and from 285 ± 12.96 to 264 ± 15.93 beats/min (p < 0.001), respectively. Human PAMP and salmon calcitonin did not change significantly PP, LVP and HR when all the respective concentrations applied.

Conclusion: 

Our results suggest that rat PAMP may produce positive chronotropic and negative inotropic effects. In contrast, rat calcitonin may induce a negative chronotropic effect.