Effects of hypoxia and isoflurane on liver blood flow: the role of adenosine.

We investigated the role of endogenous adenosine in mediating the effects of hypoxia and isoflurane on portal tributary blood flow (PTBF) and hepatic arterial blood flow (HABF) in rats. Liver blood flows were determined using radiolabelled microspheres. Hypoxia resulting from the exposure of rats to an atmosphere containing 15% oxygen for 30 min decreased PTBF (23%) (P<0.05) and cardiac index (15%) (P<0.05), and increased HABF (78%) (P<0.05). Isoflurane (1.4 vol%) increased HABF in both normoxic and hypoxic conditions but did not affect PTBF. The adenosine receptor antagonist 8-phenyltheophylline attenuated the hypoxia-induced increase in HABF but did not affect that resulting from the administration of isoflurane. In conclusion, in contrast to the increase in HABF induced by hypoxia, that induced by isoflurane appears to be independent of endogenous adenosine.