Action of coenzyme A on adenine derivative receptors in isolated tissues

The action of Coenzyme A (CoA) was investigated on the mechanical activity of four isolated tissues known to possess adenine derivative (AD) receptors that are sensitive, or resistant to blockade by theophylline. CoA produced a dose-related inhibition of the electrically stimulated myenteric plexus longitudinal muscle of the guinea pig ileum, and of the spontaneously contracting rabbit ileum. This effect was competitively antagonized by theophylline in both tissues. CoA caused a dose-related relaxation of the rat ileum. Low doses of CoA were not antagonized by theophylline but higher doses were antagonized by this drug. The rabbit detrusor, which was contracted by ATP and ADP, was not affected by CoA. Differences in the action of CoA at AD receptors in these four tissues, and in its antagonism by theophylline reflect a heterogeneity of these receptors. It is suggested that the simple sub-division of adenine derivative receptors into two types may be inappropriate.