Effects of bilateral renal denervation on open-loop baroreflex function and urine excretion in spontaneously hypertensive rats

Bilateral renal denervation (RDN) decreases arterial pressure (AP) or delays the development of hypertension in spontaneously hypertensive rats (SHR), but whether bilateral RDN significantly modifies urine output function during baroreflex-mediated acute AP changes remains unknown. We quantified the relationship between AP and normalized urine flow (nUF) in SHR that underwent bilateral RDN (n = 9) and compared the results with those in sham-operated SHR (n = 9). Moreover, we examined the acute effect of an angiotensin II type 1 receptor blocker telmisartan (2.5 mg/kg) on the AP-nUF relationship. Bilateral RDN significantly decreased AP by narrowing the response range of the total arc of the carotid sinus baroreflex. The slopes of nUF versus the mean AP (in μL·min^-1·kg^-1·mmHg^-1) in the sham and RDN groups under baseline conditions were 0.076 ± 0.045 and 0.188 ± 0.039, respectively; and those after telmisartan administration were 0.285 ± 0.034 and 0.416 ± 0.078, respectively. The effect of RDN on the nUF slope was marginally significant (P = 0.059), which may have improved the controllability of urine output in the RDN group. The effect of telmisartan on the nUF slope was significant (P < 0.001) in the sham and RDN groups, signifying the contribution of circulating or locally produced angiotensin II to determining urine output function regardless of ongoing renal sympathetic nerve activity.