Myocardial depression produced by unilateral nephrectomy in rats.

Previous experiments using 15 days renovascular hypertensive rats and their sham operated uninephrectomized controls suggested a decrease in contractile force developed by the papillary muscles from uninephrectomized rats. Because of the implications of such findings two sets of experiments were performed. The first set 15 days after operations, compared four groups of Wistar male rats: uninephrectomized, sham operated controls and renovascular hypertensive 1K1C and 2K1C. In the second set of experiments the time course effects of uninephrectomy was analysed. The first four groups of animals showed that mean blood pressure was normal in both controls and uninephrectomized rats, but the 1K1C and 2K1C groups were hypertensive. Contractile performance was analysed 24 hours after hemodynamic studies from isometric contracting left ventricle papillary muscles. Results showed similar force development in controls, 1K1C and in 2K1C muscles. However, the muscles from uninephrectomized rats showed a significant contractile depression when compared to the other groups, even under different inotropic interventions, like isoproterenol or post-rest potentiation. The study of the time course effects of uninephrectomy showed that the contractile activity is depressed 7, 15 and 30 days after unilateral nephrectomy. The results suggest that the mechanical depression, whatever its underlying mechanism, is located at the contractile machinery level.