Role of UW solution and sodium nitroprusside in reperfusion of liver xenografts from guinea-pig to rat

Guinea-pig livers are poorly reperfused when transplanted into rats. We hav e observed that, in contrast to that of the rat, the guinea-pig intrahepati c portal vein (PV) has a thick layer of smooth muscle. It is possible that, after perfusion of the liver with ice-cold saline, this could go into spas m, resulting in poor reperfusion. To test this hypothesis, guinea-pig liver s were perfused with different solutions stored at varying temperatures and transplanted into LEW rats. To prevent xenograft hyperacute rejection, all xenograft recipients were treated with 80 U/kg cobra venom factor (CVF) i. v. on days -1 and 0. In addition to the percentage reperfusion, PV resistan ce and recipient survival were also monitored. In group I, liver xenografts perfused with ice-cold saline (4 degrees C) reperfused poorly (20-30%), re sulting in the development of portal hypertension (16.5 cmH(2)O vs. 12 cmH( 2)O in naive LEW rats) and shortened mean survival time(11.7 +/- 4.2 h). In contrast, group II livers perfused with saline at room temperature (23 deg rees C) underwent homo-geneous reperfusion (98-100%) with no increase in po rtal vein resistance, indicating that low temperature was the main trigger for the spasm of the PV. Moreover, recipient survival in this group was sig nificantly prolonged to a mean of 22 +/- 2.6 h (P < 0.01). Although UW solu tion (group III) and the vasodilator sodium nitroprusside (NP) (group IV) w hen used alone improved the degree of hepatic reperfusion, it was still not optimal. The supplementation, however, of UW solution with NP in group V a nimals resulted in homogeneous reperfusion (98%) with no portal hypertensio n and consistent prolonged graft survival of 21.0 +/- 1.7 h. Therefore, thi s study has determined that the riddle of the abnormal reperfusion of guine a-pig liver xenografts by rat blood is nonimmune mediated and is due to the spasm of the strong smooth muscle in the PV tree produced by cold perfusat es.