Temporal decrease in renal sensory responses in rats after chronic ligation of the bile duct.

Renal responses to renal sensory receptor activation were examined in rats after 1 and 4 wk of common bile duct ligation (CBDL). Compared with sham-operated rats (Sham), urine and sodium excretion after acute saline loading was significantly reduced at both times after CBDL. The blunted excretory responses in CBDL rats, accompanied by less activation of afferent renal nerve activity (ARNA), were already apparent at 1 wk and became severe at 4 wk. The defect in ARNA activation in CBDL rats was further studied using specific stimuli to activate renal sensory receptors. Graded increases in intrapelvic pressure or renal pelvic perfusion of substance P (SP) elicited an increase in ARNA in Sham rats, these responses being temporally attenuated in CBDL rats. Despite no significant change in renal pelvic SP release, no renorenal reflex was demonstrable in 4-wk CBDL rats. Immunoblotting showed that expression of renal pelvic neurokinin 1 (NK-1) receptors was 32 and 47% lower in 1- and 4-wk CBDL rats, respectively, than in Sham rats, this decrease correlating well with plasma SP levels. The quantitative real-time RT-PCR showed similar levels of NK-1 receptor mRNA in the renal pelvis in the Sham and 4-wk CBDL groups. We conclude that impairment of renal excretory and sensory responses increases with the duration of cirrhosis. An impaired renorenal reflex in cirrhotic rats is involved in the defective activation of the renal sensory receptors could be due, in part, to the low expression of NK-1 receptors, which is dependent on the duration of CBDL. The decrease in NK-1 receptor protein levels is not due to a decrease in mRNA levels.