Characterization of the effects of adenosine 5'-[beta-thio]-diphosphate in rat liver.
1. In rat liver cells micromolar concentrations of adenosine 5'-[beta-thio]diphosphate (ADP beta S), activate glycogen phosphorylase by an adenosine 3':5'-cyclic monophosphate (cyclic AMP)- independent mechanism. 2. As with adenosine 5'-triphosphate (ATP), ADP beta S also inhibits the rise in cyclic AMP after glucagon. 3. Cytosolic Ca2+ measured in single cells is rapidly increased with a pattern similar for ADP beta S and for ATP. 4. At variance with ATP, ADP beta S hardly increases inositol 1,4,5-trisphosphate (IP3) levels. 5. Phorbol myristic acetate, which inhibits only slightly the glycogenolytic effect of ATP, almost completely abolishes this effect of ADP beta S. 6. With adenosine 5'-[beta-[35S]thio]diphosphate (ADP beta[35S]) as radioligand, we detected specific purinoceptors on rat liver plasma membranes. Binding consists of a major binding component with KD = 0.7 microM and Bmax = 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 ADP beta S may involve different receptors and/or different transduction mechanisms and that ADP beta[35S] can be used to detect the specific binding sites for ADP beta S.
Afdeling Biochemie, Fakulteit Geneeskunde, Leuven, Belgium.
S
S
Keppens
A
A
Vandekerckhove
H
H
De Wulf
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology; D066298:In Vitro Techniques; D007293:Inosine Triphosphate / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000187:drug effects; D013462:Sulfur Radioisotopes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology*
D011983:Receptors, Purinergic; D013462:Sulfur Radioisotopes; D013873:Thionucleotides; D007293:Inosine Triphosphate; C030812:adenosine 5'-O-(2-thiodiphosphate); D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D005934:Glucagon; D000242:Cyclic AMP; D006005:Phosphorylases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium