RETURN OF NERVE FUNCTION FOLLOWING RENAL DENERVATION IN THE PRESENCE OF ANGIOTENSIN-CONVERTING ENZYME INHIBITION IN SPONTANEOUSLY HYPERTENSIVE RATS

Abstract

Objective: Regrowth of renal nerves and functional restoration occurs following renal denervation (RDN). There is little information regarding the impact of concomitant anti-hypertensive therapies on the extent of reinnervation following RDN. Angiotensin-II has previously been shown to promote renal vessel innervation. We hypothesised that angiotensin-converting enzyme inhibition (ACEi) prolongs the antihypertensive effects of RDN by delaying renal nerve regrowth. The aim of this study was to examine the effect of ACEi treatment on the return of nerve function at 12-weeks post-RDN in spontaneously hypertensive rats (SHR). Design and method: Male SHRs (∼12 weeks of age, n > 7/group) were implanted with a radiotelemetry probe to record mean arterial pressure (MAP). Rats were infused with enalapril (1 mg/kg/day s.c.) or vehicle for two weeks. Rats then underwent sham or surgical RDN procedures and ACEi/vehicle infusion continued for an additional 12 weeks following RDN. Vascular contraction to perivascular nerve stimulation in renal lobar arteries was assessed using wire myography to determine the extent of renal nerve function return. Results: ACEi and RDN independently caused an immediate and sustained reduction in MAP (ACEi: -12 ± 3 mmHg, RDN: -19 ± 4 mmHg, both P < 0.05) across the 12-week period compared to untreated counterparts. However, the blood pressure-lowering effect of RDN was not enhanced by concomitant ACEi. Heart mass was ∼16% less in ACEi-RDN rats compared to untreated counterparts. Return of neurovascular function was observed in RDN-treated rats, but levels were only partially restored to that of untreated rats (P < 0.001). ACEi alone attenuated the response to perivascular nerve stimulation (P < 0.05) but the effects of ACEi in combination with RDN were not additive. Conclusions: Here we show partial functional reinnervation is evident 12 weeks following RDN in the SHR. This may account for the sustained reduction in MAP following RDN. ACEi infusion alone attenuated neurovascular function, but ACEi combined with RDN did not affect the return of renal neurovascular function. These findings suggest that RDN and ACEi effectively lower blood pressure in the long term and may confer cardioprotective benefits despite the return of nerve function. However, ACE inhibition does not provide additive benefits to delaying renal reinnervation.