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Characterization of the effects of adenosine 5′‐[β‐thio]‐diphosphate in rat liver
Author(s) -
Keppens Stefaan,
Vandekerckhove Ann,
Wulf H.
Publication year - 1993
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.1476-5381.1993.tb12858.x
Subject(s) - glycogen phosphorylase , adenosine diphosphate , adenosine triphosphate , adenosine , glycogenolysis , purinergic receptor , adenosine monophosphate , biochemistry , inositol phosphate , chemistry , glycogen , inositol , receptor , biology , medicine , platelet , platelet aggregation , immunology
1 In rat liver cells micromolar concentrations of adenosine 5′‐[β‐thio]diphosphate (ADPβS), activate glycogen phosphorylase by an adenosine 3′:5′‐cyclic monophosphate (cyclic AMP)‐ independent mechanism. 2 As with adenosine 5′‐triphosphate (ATP), ADPβS also inhibits the rise in cyclic AMP after glucagon. 3 Cytosolic Ca 2+ measured in single cells is rapidly increased with a pattern similar for ADPβS and for ATP. 4 At variance with ATP, ADPβS hardly increases inositol 1,4,5‐trisphosphate (IP 3 ) levels. 5 Phorbol myristic acetate, which inhibits only slightly the glycogenolytic effect of ATP, almost completely abolishes this effect of ADPβS. 6 With adenosine 5′‐[β‐[ 35 S]thio]diphosphate (ADPβ[ 35 S]) as radioligand, we detected specific purinoceptors on rat liver plasma membranes. Binding consists of a major binding component with K D = 0.7 μ m and B max = 51 pmol mg −1 of protein, probably mediating the activation of glycogen phosphorylase, and a minor high affinity, low capacity binding component with no obvious function. 7 It is concluded that the differences in biological effects between ATP and ADPβS may involve different receptors and/or different transduction mechanisms and that ADPβ[ 35 S] can be used to detect the specific binding sites for ADPβS.