Differential effects of acute thermal injury on rat splanchnic and renal blood flow and prostanoid release

This study examines the hypothesis that acute thermal injury decreases renal and splanchnic blood flow which correlates with altered endogenous vasodilator eicosanoid release. Anesthetized male Wistar rats were subjected to sham or a non-resuscitated 30% total body surface area burn. At 1, 2, 4, 8, and 24 h post-burn mean arterial pressure as well as superior mesenteric and renal artery in vivo blood flow were measured. The superior mesenteric and renal arteries were cannulated and perfused in vitro with their end organs with Krebs buffer (pH 7.4, 37°C). Renal and splanchnic 6-keto-PGF_1α (PGI₂), PGE₂, and thromboxane B₂ (TXB₂) release were measured by EIA at 15 min of perfusion. Renal and superior mesenteric artery blood flow decreased by 40% or more at 1 and 2 h post-burn despite mean arterial pressure remaining unchanged. The major eicosanoids released were PGI₂ from the splanchnic bed and PGI₂ and PGE₂ from the kidney. Splanchnic PGI₂ and TXB₂ release and renal TXB₂ increased 2-3 fold at 1 h post-burn but returned to the sham level at 2 h post-burn. By 24 h post-burn the vasodilator eicosanoids were increased in both the splanchnic and renal vascular beds. These data show that decreased renal and splanchnic blood flow was associated with increased endogenous release of the potent vasoconstrictor TXB₂. By 2 h post-burn, renal and splanchnic blood flow began returning toward the sham level as endogenous release of TXB₂ from both organs fell to sham levels. These data suggest that increased endogenous release of TXB₂ may contribute to the short-term decrease in renal and splanchnic blood flow in the immediate post-burn period and thus may contribute to ischemia of both vascular beds.