Cardiovascular responses in rats with chronic renal failure.

Cardiovascular responses were determined in rats with chronic renal failure (CRF) produced by five sixths nephrectomy and in sham-operated rats. The conscious systolic blood pressure of rats with CRF was significantly higher than the pressure in controls although, after anaesthesia, there were no significant differences in the mean arterial pressure between the two groups of rats. The pressor responses to noradrenaline in rats with CRF were not significantly different from those recorded in sham-operated controls. The bradycardia elicited by electrical stimulation of the vagus nerve was significantly diminished in rats with CRF. However, indomethacin treatment (1 mg kg-1 s.c. twice daily for 2 days) abolished the differences in response to vagal stimulation. Changes in heart rate in response to electrical stimulation of the cervical sympathetic nerve and to bolus i.v. injections of isoprenaline and carbachol were similar in rats with CRF and controls. The most notable disturbance of cardiovascular function in rats with CRF is the diminished cardiac chronotropic response to vagal stimulation which appears to be mediated by a presynaptic action of prostaglandins.