Action of adenosine and characterization of adenosine receptors in human placental vasculature.
1. Adenosine induced concentration-dependent relaxations in segments of human chorionic arteries and veins precontracted with 75 mM K+, which were attenuated by 1-methyl-3-isobutylxanthine (MIX). In the same conditions, L-phenylisopropyladenosine (L-PIA), N-ethylcarboxamideadenosine (NECA) and dibutyryl-cyclic AMP (Db-cAMP) also produced concentration-dependent vasodilations. 2. The order of potency with respect to EC50 was in arteries: NECA greater than or equal to L-PIA greater than Db-cAMP greater than or equal to adenosine, and in veins: L-PIA greater than or equal to NECA greater than adenosine greater than or equal to Db-cAMP. 3. In segments precontracted with 10(-6) M PGF2 alpha, adenosine, NECA and L-PIA induced similar relaxations, which were markedly larger than those found in K+ contracted segments. 4. Db-cAMP (15 min preincubation) inhibited more potently K+ (75 mM) contractions than adenosine. 5. Adenosine reduced Ca addition-induced contractions in depolarized segments exposed to Ca-free medium, as well as 45Ca uptake elicited by 75 mM K+. 6. It is concluded that there exists a similar population of adenosine A1 and A2 receptors in chorionic vessels, which mediate adenosine relaxation. This effect appears to be mainly produced by inhibition of Ca influx, but not by a cAMP-dependent mechanism.
Departamento de Farmacología y Psiquiatría, Facultad de Medicina, Universidad de Extremadura, Madrid, Spain.
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Reviriego
M J
MJ
Alonso
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Ibañez
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J
Marín
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D019830:Adenosine-5'-(N-ethylcarboxamide); D001808:Blood Vessels / Q000187:drug effects / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002132:Calcium Radioisotopes; D002463:Cell Membrane Permeability / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D015237:Dinoprost / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D010920:Placenta / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D011983:Receptors, Purinergic / Q000378:metabolism*
D002132:Calcium Radioisotopes; D011983:Receptors, Purinergic; D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); D003994:Bucladesine; D015237:Dinoprost; D000242:Cyclic AMP; D000241:Adenosine; D011188:Potassium; D015056:1-Methyl-3-isobutylxanthine