[3H]‐adenosine nucleotide and [3H]‐noradrenaline uptake by cold stored guinea‐pig taenia caecum; mechanical effects and release of [3H]‐adenosine nucleotide by noradrenaline, papaverine, and nitroglycerine

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Abstract
1 Cold storage (2° C) treatment progressively reduced noradrenaline uptake by the taenia caecum of the guinea-pig. After 15 days of cold treatment, [3H]-noradrenaline uptake by tissue was reduced to about 10% of control. On the other hand, prolonged cold storage failed to decrease [3H]-adenosine uptake by the taenia caecum. 2 Cocaine (10 μm) inhibited noradrenaline uptake by about 82% but nucleoside uptake was inhibited by 20%. Cocaine treatment failed to decrease the residual noradrenaline uptake in the cold stored strips (more than 10 days). Phenoxybenzamine (1 μm) or oligomycin (1 μg/ml) treatment decreased the tissue adenosine uptake to about 34% and 28% of the respective controls. 3 Based on thin layer chromatography, it was estimated that approximately 68% of [3H]-adenosine was converted into and retained as [3H]-ATP in the fresh tissues, a small fraction was accountable as [3H]-adenosine (18%) but virtually no [3H]-AMP, [3H]-cyclic AMP or [3H]-ADP was detected. Similar distribution of radioactivity of nucleotides was observed in tissues cold stored for 8 days. 4 The inhibition of the mechanical activity of taenia by noradrenaline (10 μm), papaverine (100 μm) and nitroglycerine (100 μm) was accompanied by [3H]-adenine nucleotide but not [3H]-noradrenaline release. Treatment with phentolamine and propranolol (both 1 μm) had no effect on the adenine nucleotide release elicited by nicotine and electrical field stimulation, whereas such treatment reduced the inhibitory action of both stimuli. 5 These results suggest that the nucleotide release after application of electrical and chemical stimulation may be from an extraneurogenic source. Thus, we conclude that ATP or a related nucleotide is not the chemical transmitter of the non-adrenergic inhibition in the taenia caecum of the guinea-pig.