Analysis of the effects of adenosine in skinned bovine coronary artery

We have investigated the mechanism of adenosine-induced relaxation in relation to its effects on intracellular organelles in Triton X-100- and saponin-skinned bovine coronary arteries. In intact coronary arteries, high K+ and prostaglandin F2 alpha caused sustained contractions, whereas caffeine produced transient contractions. Triton X-100 treatment abolished these contractions. However, Triton X-100-skinned coronary arteries were responsive to added free calcium. There was no significant difference between calcium concentration-response curves obtained in the absence and presence of adenosine (50 microM). Unlike Triton X-100, in saponin-skinned arteries, caffeine produced transient contractions but high K+ and prostaglandin F2 alpha did not. Adenosine had no effect on caffeine-induced contractions in saponin-skinned coronary arteries. These data suggest that adenosine had no direct inhibitory effect on either the contractile apparatus or calcium release from sarcoplasmic reticulum in coronary arteries.