EFFECTS OF ANG-CONVERTING ENZYME AND ALPHA(1)-ADRENOCEPTOR INHIBITIONON INTRARENAL HEMODYNAMICS IN SHR

To investigate the prolonged effects of angiotensin-converting enzyme (ACE) inhibition and oil-adrenoceptor blockade on intrarenal hemodynam ics, whole kidney and renal micropuncture studies were performed in ma le 21-wk-old Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) r ats treated for 3 wk with quinapril (3 mg/kg), terazosin (1 mg/kg), or in their combination (quinapril 1.5 mg/kg and terazosin 0.5 mg/kg). I n WKY, only quinapril significantly reduced mean arterial pressure (MA P) associated with reduced afferent arteriolar resistance; there were no other significant changes. In contrast, all treatments similarly de creased MAP in SHR, Quinapril increased renal plasma flow and decrease d filtration fraction. With respect to intrarenal hemodynamics, quinap ril increased single-nephron plasma flow and reduced glomerular capill ary pressure (from 53.1 to 47.8 mmHg; P < 0.01), associated with reduc ed afferent (from 4.80 to 3.17 10(10)dyn . s . cm(-5); P < 0.01) and e fferent (from 1.70 to 1.17 10(10)dyn . s . cm(-5); P < 0.01) arteriola r resistances, and increased ultrafiltration coefficient (from 0.037 t o 0.052 nl . s(-1) . mmHg(-1); P < 0.05). Terazosin only reduced arter iolar resistance. The combined treatment attenuated either agent's ind ependent effects on glomerular hemodynamics. These data demonstrate th at prolonged ACE and adrenergic inhibition therapy alone or in combina tion produce different effects than when given by vein, suggesting tha t prolonged renopressor system inhibition may be more effective than a drenergic in SHR.