Adenosine participates in regulation of smooth muscle relaxation in aortas from rats with experimental hypothyroidism.
The contribution of adenosine receptors was evaluated in vascular relaxation in experimental hypothyroidism. Hypothyroid aortic rings contracted less than normal controls with noradrenaline, phenylephrine, and KCl; the difference was maintained after incubation with 1,3-dipropyl-8-p-sulfophenylxanthine (an A1 and A2 adenosine receptor blocker). The vascular relaxation induced by acetylcholine or carbachol was similar in normal and hypothyroid aortic rings. However, adenosine, N6-cyclopentyladenosine (an A1 adenosine receptor analogue), and 5'-N-ethylcarboxamidoadenosine (an A2 and A3 adenosine analogue) induced vasodilation that was larger in hypothyroid than in normal aortas. Nomega-nitro-L-arginine methyl ester shifted the dose-response curves of adenosine, N6-cyclopentyladenosine, or 5'-N-ethylcarboxamidoadenosine to the right in both normal and hypothyroid vessels. The blocker 1,3-dipropyl-8-p-sulfophenylxanthine significantly reduced adenosine-induced relaxation in the hypothyroid but not in the normal aortic vessels. These results suggest that in hypothyroid aortas, a larger adenosine-mediated vasodilation is observed probably due to an increase in receptor number or sensitivity.
Department of Biochemistry, Instituto Nacional de Cardiología Ignacio Chávez, México City, México.
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G
Baños
F
F
Martínez
J I
JI
Grimaldo
M
M
Franco
D000241:Adenosine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007037:Hypothyroidism / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D013965:Thyroidectomy; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014662:Vasoconstrictor Agents; D014970:Xanthines; D010656:Phenylephrine; C053896:1,3-dipropyl-8-(4-sulfophenyl)xanthine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D000241:Adenosine; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine