Differential coronary microvascular exchange responses to adenosine: roles of receptor and microvessel subtypes.
OBJECTIVE
To assess the role of adenosine receptors in the regulation of coronary microvascular permeability to porcine serum albumin (P(s)(PSA)).


METHODS
Solute flux was measured in single perfused arterioles and venules isolated from pig hearts using fluorescent dye-labeled probes by microspectro-fluorometry. Messenger RNA, protein, and cellular distribution of adenosine receptors in arterioles and venules were analyzed by RT-PCR, immunoblot, and immunofluorescence.


RESULTS
Control venule P(s)(PSA) (10.7 +/- 4.8 x 10(- 7) cm x s(- 1)) was greater than that of arterioles (6.4+/- 2.8 x 10(-7) cm . s(-1); p < .05). Arteriolar P(s)(PSA) decreased (p < .05) with adenosine suffusion over the range from 10(- 8) to 10(-5) M, while venular P(s)(PSA) did not change. The nonselective A(1) and A(2) receptor antagonist, 8-(p-sulfophenyl) theophylline, blocked the adenosine-induced decrease in arteriolar P(s)(PSA). Messenger RNA for adenosine A(1), A(2A), A(2B), and A(3) receptors was expressed in arterioles and venules. Protein for A(1), A(2A), and A(2B), but not A(3), was detected in both microvessel types and was further demonstrated on vascular endothelial cells.


CONCLUSIONS
Arteriolar P(s)(PSA) decreases with adenosine suffusion but not venular P(s)(PSA). Adenosine A(1), A(2A), and A(2B) receptors are expressed in both arterioles and venules. Selective receptor-linked cellular signaling mechanisms underlying the regulation of permeability remain to be determined.
Wang
Jianjie
J
Department of Physiology and Pharmacology, School of Medicine, University of Missouri, Columbia, Missouri, USA.
Whitt
Stevan P
SP
Rubin
Leona J
LJ
Huxley
Virginia H
VH
D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000737:chemistry; D002199:Capillary Permeability; D003326:Coronary Circulation / Q000502:physiology*; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008833:Microcirculation; D008856:Microscopy, Fluorescence; D010477:Perfusion; D012333:RNA, Messenger / Q000032:analysis; D043682:Receptor, Adenosine A1 / Q000032:analysis / Q000235:genetics / Q000502:physiology; D043705:Receptor, Adenosine A2A / Q000032:analysis / Q000235:genetics / Q000502:physiology; D043704:Receptor, Adenosine A2B / Q000032:analysis / Q000235:genetics / Q000502:physiology; D043684:Receptor, Adenosine A3 / Q000032:analysis / Q000235:genetics / Q000502:physiology; D018047:Receptors, Purinergic P1 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D012709:Serum Albumin / Q000378:metabolism; D013552:Swine; D014699:Venules / Q000737:chemistry
D005456:Fluorescent Dyes; D012333:RNA, Messenger; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D012709:Serum Albumin; D000241:Adenosine