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INTERACTIONS BETWEEN THE EFFECTS OF α‐ AND β‐ADRENOCEPTOR AGONISTS AND ADENINE NUCLEOTIDES ON THE MEMBRANE POTENTIAL OF CELLS IN GUINEA‐PIG LIVER SLICES
Author(s) -
JENKINSON D.H.,
KOLLER KARIN
Publication year - 1977
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1977.tb06991.x
Subject(s) - agonist , isoprenaline , adenosine , chemistry , intracellular , nucleotide , membrane potential , adenosine triphosphate , guinea pig , alpha (finance) , biochemistry , biophysics , medicine , pharmacology , endocrinology , receptor , biology , stimulation , construct validity , nursing , gene , patient satisfaction
1 The β‐adrenoceptor agonist isoprenaline normally causes only a small and inconsistent increase in the membrane potential of cells in guinea‐pig liver slices, in contrast to the large hyperpolarizations seen with α‐agonists. However, after a selective α‐adrenoceptor agonist has been applied, the response to isoprenaline becomes greatly enhanced. 2 Simultaneous application of small doses of an α‐ and a β‐agonist produce hyperpolarizations larger than the sum of the responses to each agent alone. 3 These interactions occur with a range of sympathomimetic amines, including some which are not substrates for various processes for the uptake and inactivation of catecholamines. 4 Hyperpolarizations caused by externally applied cyclic adenosine‐3′,5′‐monophosphate (cyclic AMP) also become larger after application of an α‐agonist. 5 The adenine nucleotides adenosine 5′‐diphosphate (ADP) and adenosine 5′‐triphosphate (ATP) hyperpolarize guinea‐pig liver cells in the dose range 0.1‐1.0 m m . This response is not increased after an α‐agonist. However, ADP and ATP are themselves able to enhance the response to β‐agonists. 6 These interactions between α‐agonists, β‐agonists and adenine nucleotides seem to involve steps subsequent to receptor activation. Changes in the intracellular actions of cyclic AMP may be concerned.