DOPAMINE INCREASES RENAL MEDULLARY BLOOD-FLOW WITHOUT IMPROVING REGIONAL HYPOXIA

The effects of dopamine (10 mu g/kg/min i.v.) upon intrarenal microcir culation, total, superficial cortical and outer medullary blood flows and outer medullary pO(2) were continuously determined in anesthetized rats with ultrasonic and laser-Doppler probes and oxygen microelectro des. While total and cortical flows were unaffected, outer medullary f low increased by 35 +/- 5% (mean +/- SE, p < 0.01). Outer medullary pO (2) was not significantly altered (from 16 +/- 4 to 18 +/- 4 mm Hg). I n volume-expanded rats total and cortical flows rose as well. In rats pretreated with indomethacin, with or without N omega-nitro-L-arginine methyl ester HCl, dopamine restored renal microcirculation and amelio rated outer medullary hypoxia.