Interaction between hemorrhagic hypotension and hypoxia in regulation of renal vascular resistance in unanesthetized rabbits.
Effects of interaction between hemorrhagic hypotension and hypoxia on the renal circulation were examined in awake rabbits. The hypothesis tested was that renal vasoconstriction during hemorrhagic hypotension is affected by arterial PO2 (PaO2). Awake rabbits were placed into an environmental chamber and exposed to either normoxia (PaO2 greater than 100 mmHg) or hypoxia (PaO2 less than or equal to 40 mmHg). Renal blood flow (RBF) was measured with 15 micron microspheres during normotension (mean arterial pressure = 86-97 mmHg), moderate hemorrhagic hypotension (mean arterial pressure = 62-65 mmHg), and severe hemorrhagic hypotension (mean arterial pressure = 49-50 mmHg). During normotension, RBF was 461 +/- 46 and 330 +/- 30 ml/min per 100 g (mean +/- SEM) in the normoxic and hypoxic groups, respectively (P less than 0.05), and renal vascular resistance (RVR) was 0.21 +/- 0.03 and 0.31 +/- 0.04 mmHg per ml/min per 100 g in the normoxic and hypoxic groups, respectively (NS). Renal blood flow fell progressively in each group during hypotension, but the magnitude of this response was unaffected by the level of PaO2. In contrast, RVR during severe hypotension was 0.42 +/- 0.11 and 2.08 +/- 0.57 mmHg per 100 g for normoxia and hypoxia, respectively (P less than 0.05), and the increase in RVR during severe hypotension compared to normotension was greater in the hypoxic than normoxic group (P less than 0.05). Thus, in unanesthetized rabbits, hypoxia reduces RBF but does not change RVR significantly during normotension, and hypoxia potentiates the increase in RVR during hemorrhagic hypotension.
D000818:Animals; D005260:Female; D006470:Hemorrhage / Q000503:physiopathology*; D007022:Hypotension / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D011817:Rabbits; D012039:Regional Blood Flow; D012079:Renal Circulation; D014655:Vascular Resistance; D014661:Vasoconstriction
D010100:Oxygen