Hepatorenal reflex in the rat

The possible existence of a hepatorenal reflex was evaluated in male Sprague-Dawley rats. Sodium excretion was measured in two groups of six rats each, during the first 4 h following acute ingestion of a known amount of high salt chow (2.0-2.5 mequiv. NaCl). Hourly excretion rates for sodium before surgery were compared with results following 7 days of recovery from either hepatic denervation (n = 6) or sham denervation (n = 6). Before denervation, hourly sodium excretion between the groups was not different. Following surgery for hepatic denervation, sodium excretion was 91% lower than presurgery values for the 1st h (p < 0.02) and 44% lower in the 2nd h (p < 0.04). Sham denervation caused no significant change in sodium excretion when compared with presurgery results. A test for completeness of denervation showed that norepinephrine concentration in liver tissue taken from denervated rats was 5.1 +/- 8 ng/g and that taken from sham rats was 22.8 +/- 1 ng/g (p < 0.001). These data demonstrate that the liver is essential for the normal postprandial excretion of sodium following ingestion of a high salt meal in rats.