The response of isolated guinea-pig aorta to amrinone.
1. In helically cut strips of aorta from reserpine-treated guinea-pigs, cumulative concentrations (30 microM, 0.3 mM and 3 mM) of amrinone progressively reduced the basal tone of the preparations and relaxed the smooth muscle contracted by 1 microM noradrenaline or by 20 mM K+. 2. The relaxing effect was completely suppressed by tissue pretreatment with adenosine deaminase (1 U ml-1). 3. Relaxation induced by amrinone was not affected by 50 microM indomethacin or by 0.1 mM 8-phenyltheophylline and was potentiated by 5 microM quinidine. 4. Like amrinone, exogenous adenosine reduced the basal tone of the guinea-pig aorta strips and relaxed the preparations contracted by 1 microM noradrenaline or by 20 mM k+ in a concentration-dependent manner. 5. The relaxing activity of exogenous adenosine was not affected by 50 microM indomethacin, was potentiated by 5 microM quinidine and was partially antagonized by 0.1 mM 8-phenyltheophylline. 6. These results indicate the involvement of endogenous adenosine in the relaxing effect of amrinone on guinea-pig aorta strips, but the specific mechanism of amrinone-adenosine interaction remains to be elucidated.
Dorigo
P
P
Department of Pharmacology, University of Padova, Italy.
Ceroni
G
G
Giacometti
A
A
Valentini
E
E
Gaion
R M
RM
Maragno
I
I
D000241:Adenosine / Q000494:pharmacology; D000243:Adenosine Deaminase / Q000494:pharmacology; D000676:Amrinone / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011802:Quinidine / Q000494:pharmacology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
D013806:Theophylline; C028322:8-phenyltheophylline; D000243:Adenosine Deaminase; D011802:Quinidine; D000676:Amrinone; D000241:Adenosine; D007213:Indomethacin