NUCLEOTIDE PYROPHOSPHATASE ANTAGONIZES RESPONSES TO ADENOSINE 5′ ‐TRIPHOSPHATE AND NON‐ADRENERGIC, NON‐CHOLINERGIC INHIBITORY NERVE STIMULATION IN THE GUINEA‐PIG ISOLATED TAENIA COLI

Abstract

The enzyme, nucleotide pyrophosphatase converted adenosine 5′ -triphosphate (ATP) to adenosine 5′ -monophosphate (AMP). In the isolated taenia coli of the guinea-pig it reduced the inhibitory responses to exogenously applied ATP. This could be explained on the basis that the ATP was rapidly converted to AMP which is less potent. The enzyme also reduced inhibitory responses to stimulation of non-adrenergic, non-cholinergic nerves but failed to reduce inhibitory responses to either perivascular sympathetic nerve stimulation or to noradrenaline. The results support the hypothesis that ATP is the transmitter released by non-adrenergic, non-cholinergic (‘purinergic’) inhibitory nerves.