Endothelial cell uptake of adenosine in canine skeletal muscle
Gorman, M.W.; Bassingthwaighte, J.B.; Olsson, R.A.; Sparks, H.V.
American Journal of Physiology 250(3 Pt 2): H482-H489
1986
ISSN/ISBN: 0002-9513 PMID: 3513628 Document Number: 268922
The vascularly isolated muscles in the hindlimbs of five dogs were perfused with an oxygenated physiological salt solution. The extractions of adenosine and of a nontransported analogue of adenosine, 9-.beta.-D-arabinofuranosyl hypoxanthine (AraH), were determined by the single-pass indicator-dilution technique. A bolus containing [125I]albumin (reference tracer), [14C]adenosine, and [3H]AraH was injected into the artery while samples of venous effluent were collected over the next minute. This injection was repeated with dipyridamole (10-5 M) in the perfusate. Early extractions of AraH (EAra) and adenosine (EAdo) under control conditions were 48 .+-. 4 and 80 .+-. 4%, respectively. In the presence of dipyridamole, EAra was unchanged (47 .+-. 5) while EAdo decreased to 45 .+-. 7%. Since early extraction reflects primarily the barrier posed by endothelial cells, these results demonstrate significant endothelial uptake of adenosine. Analysis of these data using a mathematical model of blood-tissue exchange indicates that, under the conditions of these experiments, at least 78% of the adenosine taken up by skeletal muscle entered endothelial cells.