ENALAPRILAT RESTORES SENSITIVITY OF BAROREFLEX CONTROL OF RENAL AND TOTAL NORADRENALINE SPILLOVER IN HEART-FAILURE RABBIT

1. The acute effect of an angiotensin converting enzyme inhibitor (ACE I), enalaprilat, on baroreflex-mediated changes in renal and total NA spillover rate in conscious rabbits with doxorubicin-induced cardiomyo pathic congestive heart failure (CHF) were investigated under resting conditions and in response to changes in arterial pressure induced by sodium nitroprusside and phenylephrine infusions. 2. Six saline-treate d (N group) and 11 doxorubicin-treated rabbits (1 mg/kg administered i .v. twice weekly) were studied after 4 and 6 weeks treatment. Five CHF rabbits received saline (C group) and six enalaprilat infusion (ACEI group). 3. After 4 weeks of doxorubicin, mean arterial pressure (MAP)- renal noradrenaline (NA) spillover and MAP-total NA spillover curves d id not change during enalaprilat infusion. 4. After 6 weeks, the C gro up showed blunted MAP-renal NA spillover and MAP-total NA spillover cu rves. In the ACEI group, however, both curves returned toward those se en in the N group (slope of MAP-renal NA curve: from 0.27 to 1.80 ng/m in per mmHg, MAP-total NA curve: from 1.61 to 3.59 ng/min per mmHg). 5 . Results of this study indicate that enalaprilat enhances baroreflex control of renal and total NA spillover in rabbits with CHF and furthe r support the view that activation of the renin-angiotensin system con tributes significantly to the attenuated baroreflex responses in CHF.