Intrinsic sympathomimetic activity ofcardioselective r3-adrenoceptor blockers andeffects onrenal function

1 Theeffects ofa21infusion ofisotonic sodium chloride onrenal haemodynamics and sodium excretion weremeasured inninenormotensive volunteers. 2 Changes inthese responses tovolumeexpansion induced bycardioselective adrenoceptor blockade bydrugs with(epanolol) andwithout intrinsic sympathomimetic activity (atenolol) wereexamined. 3 Renalplasma flowwassignificantly lower before, during andafter sodium chloride infusion whilst ontreatment withatenolol compared withepanolol. 4 Urinary sodium excretion waslower onatenolol thanepanolol. 5 Glomerular filtration rate wasunchanged byeither drug. 6 Basal urinary kallikrein excretion wasdiminished byatenolol andbothepanolol and atenolol inhibited therise inurinary kallikrein excretion after sodium chloride infusion. 7 Although someofthese findings maybeduetoamorepotent hypotensive effect of atenolol, intrinsic sympathomimetic activity maycontribute totheapparent protective effects ofepanolol onrenal function.