AIMS/ BACKGROUND: In the sinusoidal bed the distribution of water is flow-limited, but it becomes partly barrier-limited when adenosine triphosphate (ATP) is introduced. This effect could be exerted either directly by ATP or by substances released from presinusoidal regions. Furthermore, portally infused ATP seems to be able to diffuse in the direction of the arterial bed. It is not known if this diffusion route is specific. Answers to these questions can be obtained from indicator-dilution experiments in retrograde perfusion. METHODS: Indicator-dilution experiments, using [14C]sucrose and [3H]water, were conducted. Rat livers were perfused in the retrograde mode (hepatic vein+hepatic artery --> portal vein). RESULTS: When ATP was infused into the hepatic vein, the distribution of [3H]water remained essentially flow-limited. The infusion of ATP into the hepatic artery increased the sucrose and extra-sucrose spaces of the arterial bed, but infusion into the hepatic vein was without effect. CONCLUSIONS: The results indicate that the induction of barrier-limited distribution of [3H]water is not a direct effect of ATP. Furthermore, if the transhepatic diffusion of ATP can occur from presinusoidal regions to the arterial bed, as shown by previous work, a similar diffusion does not occur from postsinusoidal regions.
AIMS/ BACKGROUND: In the sinusoidal bed the distribution of water is flow-limited, but it becomes partly barrier-limited when adenosine triphosphate (ATP) is introduced. This effect could be exerted either directly by ATP or by substances released from presinusoidal regions. Furthermore, portally infused ATP seems to be able to diffuse in the direction of the arterial bed. It is not known if this diffusion route is specific. Answers to these questions can be obtained from indicator-dilution experiments in retrograde perfusion. METHODS: Indicator-dilution experiments, using [14C]sucrose and [3H]water, were conducted. Rat livers were perfused in the retrograde mode (hepatic vein+hepatic artery --> portal vein). RESULTS: When ATP was infused into the hepatic vein, the distribution of [3H]water remained essentially flow-limited. The infusion of ATP into the hepatic artery increased the sucrose and extra-sucrose spaces of the arterial bed, but infusion into the hepatic vein was without effect. CONCLUSIONS: The results indicate that the induction of barrier-limited distribution of [3H]water is not a direct effect of ATP. Furthermore, if the transhepatic diffusion of ATP can occur from presinusoidal regions to the arterial bed, as shown by previous work, a similar diffusion does not occur from postsinusoidal regions.