Cardiac beta-receptors in experimental Chagas' disease.

Experimental Chagas' disease (45 to 90 days post-infection) showed serious cardiac alterations in the contractility and in the pharmacological response to beta adrenergic receptors in normal and T. cruzi infected mice (post-acute phase). Chagasic infection did not change the beta receptors density (78.591 +/- 3.125 fmol/mg protein and 73.647 +/- 2.194 fmol/mg protein for controls) but their affinity was significantly diminished (Kd = 7.299 +/- 0.426 significantly diminished (Kd = 7.299 +/- 0.426 nM and Kd = 3.759 +/- 0.212 nM for the control) p < 0.001. This results demonstrate that the alterations in pharmacological response previously reported in chagasic myocardium are related to a significantly less beta cardiac receptor affinity. During this experimental period serious cardiac cell alterations take place and functional consequences will be detected in the chronic phase.