Brief mesenteric ischemia increases PGE2, but not PGI2, in intestinal lymph of cats

Mesenteric ischemia of short duration (5-10 min) can stimulate A delta- and C-fiber afferent nerve endings in the viscera to reflexly activate the cardiovascular system. The mechanism of activation of abdominal visceral afferents is probably multifactorial and may involve prostaglandins (PGs), which have been shown to directly stimulate and/or sensitive visceral afferents when administered exogenously. We hypothesized that brief visceral ischemia is accompanied by release of PGI2 and PGE2 into the interstitium, where these cyclooxygenase products could stimulate or sensitize visceral afferent nerve endings. Accordingly, we measured immunoreactive PGE2 (iPGE2) and 6-keto-PGF1 alpha (i6-keto-PGF1 alpha), the stable metabolite of PGI2, in lymph draining the ischemic viscera as well as in portal venous blood. An intestinal lymph duct distal to the lymph node was cannulated in pentobarbital sodium-anesthetized cats. Lymph and plasma iPGE2 and i6-keto-PGF1 alpha concentrations were measured by radioimmunoassay before, during, and immediately after a 5- to 10-min occlusion of the descending aorta. The i6-keto-PGF1 alpha concentration increased significantly (P < 0.001) in portal venous plasma (61 +/- 12 to 107 +/- 18 pg/0.1 ml; n = 14) but not in lymph (148 +/- 30 to 159 +/- 24 pg/0.1 ml; n = 16). In contrast, iPGE2 concentration was significantly (P < 0.01) elevated in both venous plasma (156 +/- 16 to 207 +/- 26 pg/0.1 ml; n = 19) and lymph (520 +/- 48 to 590 +/- 52 pg/0.1 ml; n = 20).(ABSTRACT TRUNCATED AT 250 WORDS)