Inhibition of contractions and 45Ca influx by adenosine in rabbit aorta.
The effects of adenosine on contractility and 45Ca-uptake in rabbit aorta have been examined and compared with those of nifedipine. Both adenosine (10(-5) M) and nifedipine (10(-8) M) inhibited contractions caused by CaCl2 (0.1-10 mM) in K(+)-depolarized preparations. Nifedipine (10(-7) M) significantly inhibited the contractions of noradrenaline (NA) at all doses (10(-8)-10(-4) M), while adenosine inhibited the contractions induced only by lower doses of NA (10(-8) and 10(-7) M) without affecting those at higher doses (greater than 10(-7) M). Adenosine (10(-8) M) and nifedipine (10(-7) M) inhibited K(+)-stimulated 45Ca-uptake by aortic strips by 75 and 100%, respectively. Similarity, NA (10(-4) M)-stimulated 45Ca influx was inhibited by about 70% by both these agents. The results suggest that adenosine inhibits inward Ca2+ movement involving both voltage-operated and receptor-operated calcium channels in rabbit aortic smooth muscle.
Parija
S C
SC
Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar.
Raviprakash
V
V
Mishra
S K
SK
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000037:antagonists & inhibitors*; D002132:Calcium Radioisotopes; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D011817:Rabbits
D002132:Calcium Radioisotopes; D009543:Nifedipine; D000241:Adenosine; D002122:Calcium Chloride; D002118:Calcium; D009638:Norepinephrine