Effects of leukotrienes B4, C4, and D4 on rat mesenteric microcirculation

Arachidonic acid is metabolized to leukotriene (LT) B4, C4, D4, and E4 by lipoxygenase. LTB4 is a chemotactic agent while LTC4 and LTD4 stimulate smooth muscle fibers to contract. Mesenteric vessels have the capacity to release leukotrienes. The possibility that leukotrienes might be responsible for or contribute to mesenteric ischemia during mesenteric low flow, embolism, and thrombosis prompted us to investigate their action on mesenteric vessels. LTB4, C4, and D4 were applied topically on small bowel mesentery of 22 Sprague-Dawley rats in sequentially increasing concentrations. Mesenteric arterioles with diameters of 8-20 microns were observed through a microscope and vessel diameters were measured using a video shear monitor. LTB4 had no effect on diameter, but doses as low as 3 X 10(-8) M induced white blood cell adherence to venular endothelium, reflecting the potent chemotactic properties of this compound. LTC4 and D4 had no effect on systemic blood pressure or white blood cell adherence. Applications of 6.4 X 10(-9), 3.2 X 10(-8), and 6.4 X 10(-8) M LTC4 decreased mesenteric arteriolar diameter to 85.3* +/- 4.7% (mean +/- SD), 75.7* +/- 7.5%, and 66.8* +/- 6.1% of baseline, and 4 X 10(-9), 2 X 10(-8), and 4 X 10(-8) M LTD4 decreased diameter to 84.9* +/- 6.1%, 75.1* +/- 4.2%, and 64.1* +/- 5% of baseline, respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)