Inhibition by extracellular ATP of organic anion transport in the perfused rat liver

Role of Extracellular Adenosine Triphosphate in Human Skin

Background:

The nucleotide adenosine triphosphate (ATP) has long been known to drive and participate in countless intracellular processes. Extracellular ATP and its metabolite adenosine have also been shown to exert a variety of effects on nearly every cell type in human skin. Knowledge of the sources and effects of extracellular ATP in human skin may help shape new therapies for skin injury, inflammation, and numerous other cutaneous disorders.

Objective:

The objective of this review is to introduce the reader to current knowledge regarding the sources and effects of extracellular ATP in human skin and to outline areas in which further research is necessary to clarify the nature and mechanism of these effects.

Conclusion:

Extracellular ATP seems to play a direct role in triggering skin inflammatory, regenerative, and fibrotic responses to mechanical injury, an indirect role in melanocyte proliferation and apoptosis, and a complex role in Langerhans cell-directed adaptive immunity.

Cellular Distribution and Functions of P2 Receptor Subtypes in Different Systems

This review is aimed at providing readers with a comprehensive reference article about the distribution and function of P2 receptors in all the organs, tissues, and cells in the body. Each section provides an account of the early history of purinergic signaling in the organ?cell up to 1994, then summarizes subsequent evidence for the presence of P2X and P2Y receptor subtype mRNA and proteins as well as functional data, all fully referenced. A section is included describing the plasticity of expression of P2 receptors during development and aging as well as in various pathophysiological conditions. Finally, there is some discussion of possible future developments in the purinergic signaling field.

The hemodynamic effects of ATP in retrograde perfusion of the bivascularly perfused rat liver

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.