Thromboxane A2 analogue contracts predominantly the hepatic veins in isolated canine liver.
Thromboxane A2 (TxA2) is a potent vasoconstrictor and has been implicated as a mediator of liver diseases such as ischemic-reperfusion injury. We determined the effects of TxA2 and the well-known hepatic venoconstrictor histamine, on the vascular resistance distribution and liver weight in isolated canine livers perfused with blood via the portal vein. The stable TxA2 (STA2; 20 micrograms, n = 5) and histamine (5 micrograms, n = 6) similarly increased the hepatic total vascular resistance, 2.5- and 2.4-fold, respectively. The increase in the hepatic venous resistance was significantly greater than that of the portal resistance (threefold vs. 1.9-fold for STA2; threefold vs. 1.8-fold for histamine). Predominant hepatic venoconstriction induced by both agents was confirmed in livers perfused in a reverse direction from the hepatic vein to the portal vein, as shown by marked precapillary vasoconstriction. STA2 transiently increased liver weight loss (-3.6 g/100 g liver weight), followed by a gradual weight gain (9.0 g/100 g). Histamine caused a progressive weight gain (9.1 g/100 g). In conclusion, similar to histamine, TxA2 constricts predominantly the hepatic vein in isolated canine livers.
Urayama
H
H
Department of Physiology, Shinshu University School of Medicine, Matsumoto, Japan.
Shibamoto
T
T
Wang
H G
HG
Koyama
S
S
D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects; D006503:Hepatic Veins / Q000187:drug effects*; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000098:blood supply* / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D010477:Perfusion / Q000379:methods; D013928:Thromboxane A2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D013928:Thromboxane A2; C037866:STA 2; D006632:Histamine