A comparison of adenine and some derivatives on pig isolated tracheal muscle.

We studied the muscle relaxation induced by adenine and several adenine derivatives in strips of tracheal smooth muscle from pigs; in addition their metabolism by the tissue was examined. Adenine relaxed tissue which was contracted by carbachol, histamine, or KCl. Adenine's potency was similar to that of adenosine and ATP (threshold about 4 X 10(-5)M). In tissues with carbachol-induced tone, the adenine effect differed from adenosine and ATP by being slower in onset and in 'washout' time. Furthermore, neither dipyridamole nor theophylline modified the response to adenine. The relationship was examined between pharmacological effects and the metabolism of [3H]-adenosine and [3H]-adenine. Both substrates were taken up by the tissue and converted to nucleotides, but relaxation correlated with nucleotide accumulation only in the case of [3H]-adenine. We conclude that the site and mechanism of adenine-induced relaxation is different from that of adenosine and ATP in porcine tracheal muscle.