Abstract
Exogenously applied ATP causes a rapid contraction of the isolated guinea-pig vas deferens preparation and is a candidate as a cotransmitter mediating the twitch component of the response to sympathetic nerve stimulation in the preparation.
The enzyme nucleotide pyrophosphatase converts ATP to AMP which is inactive in the vas deferens preparation. In preparations treated with the enzyme, contractions to ATP were markedly reduced compared to control untreated preparations. Contractions in response to sympathetic nerve stimulation were reduced in amplitude only slightly by nucleotide pyrophosphatase treatment although the peak of the initial twitch component was abolished leaving the slower phasic component. The drug phentolamine abolished the slower phasic response to sympathetic nerve stimulation which is attributed to the noradrenaline component of the cotransmission but the initial twitch component was not reduced. In phentolamine treated preparations, nucleotide pyrophosphatase caused a marked reduction of the response to sympathetic nerve stimulation. Nucleotide pyrophosphatase failed to affect contractions due to noradrenaline in phentolamine-free preparations.
The finding that nucleotide pyrophosphatase selectively antagonised the twitch component of the response to sympathetic nerve stimulation and contractions to ATP supports the idea that ATP is a cotransmitter in the tissue.
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Satchell, D. 136 NUCLEOTIDE PYROPHOSPHATASE ANTAGONIZES CONTRACTIONS DUE TO THE TWITCH COMPONENT OF THE SYMPATHETIC NERVE RESPONSE AND TO APPLIED ATP IN THE GUINEA-PIG VAS DEFERENS. Pediatr Res 24, 133 (1988). https://doi.org/10.1203/00006450-198807000-00160
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DOI: https://doi.org/10.1203/00006450-198807000-00160