Abstract
In guinea-pig ileum adenosine and adenosine analogs act presynaptically to inhibit cholinergic transmitter release and this has been shown to be due to actions at A1 (Ri) receptors. The I.C.50 of adenosine on the twitch response of this tissue is about 2μM. The purine content of the medium and tissues was measured throughout the pharmacological studies. The tissue released purines into the medium at 7.8±1.0 SEM pmol/mg/min and this was mostly uric acid. NAD (2μM) was rapidly hydrolysed to 5'-AMP (2.8±0.3pmol/mg /min). Both 5'- and 2'-AMP formed adenosine (2.8±0.6 and 3.2±0.6 pmol/mg/min). Adenosine was deaminated (3.2±0.2 pmol/mg/min) then oxidised to uric acid. Deoxycoformycin (dCF, 2μM) increased adenosine to 1-2μM in the medium from all substrates but the effect of adenosine on the twitch was not simply related to the increased adenosine concentration except when adenosine itself was the substrate, when a linear correlation was found between the inhibition of twitch response and the concentration of adenosine in the medium.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
