Uptake and release of adenosine by cultured rat aortic smooth muscle.
We wanted to determine whether CO2, H+ and K+ affect the adenosine metabolism of vascular smooth muscle in a way that could account for the effects of these substances on vascular reactivity and their ability to modulate adenosine-induced vascular relaxation. Accordingly, 1-week-old cultures of rat aortic smooth muscle were incubated in phosphate-buffered saline with various [K+]'s and pH's and aerated in an incubation chamber with gases containing various proportions of CO2. Uptake was measured as 14C incorporation into cellular constituents during exposure to 2 microM [14C]adenosine. Release was measured as net extracellular adenosine accumulation. Uptake of adenosine was not significantly affected by any of the experimental maneuvers, except that it was greatly attenuated by dipyridamole (10(-5) and 10(-4) M) and transiently enhanced by the low CO2 levels. Adenosine release, however, was depressed by lowering atmospheric CO2 (0% vs 5%) and also by normocapnic acidosis (pH 6.8 vs pH 7.4). We conclude that vascular smooth muscle in culture releases adenosine at a rate that might have vasoactive significance in vivo. Furthermore, some of the vascular actions of CO2 and H+, but not those of K+, may be partially explained by their effects on vascular smooth muscle's adenosine metabolism.
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D002245:Carbon Dioxide; D000241:Adenosine; D011188:Potassium