Ectonucleotidases

Expression of Purinergic Receptor Channels and Their Role in Calcium Signaling and Hormone Release in Pituitary Gonadotrophs

“…Like ecto-ATPase, ecto-ADPase and ecto-5Ј-nucleotidase are also inhibited by depletion of Ca 2ϩ and Mg 2ϩ (27). In accord with this, in cells perifused with or bathed in EDTA-containing medium, more than 90% recovery of added ATP was detected.…”

“…Total concentration of adenosine nucleotides was also measured in several experiments, by employing the following enzymatic reactions to convert ADP and AMP to ATP (27,28),…”

“…In accord with this, in cells perifused with or bathed in EDTA-containing medium, more than 90% recovery of added ATP was detected. Furthermore, in Ca 2ϩ -containing medium, addition of 50 M ␣,␤-methylene-ADP, an inhibitor of 5Ј-ectonucleotidase (27,28) led to almost complete recovery of exogeneously added ATP in static cultures and to about 40% recovery in perifusate. As shown in Table I, basal secretion of ATP also increased in cells exposed to ␣,␤-methylene-ADP.…”

“…Such a rapid degradation of ATP in the presence of the cells indicated the operation of ecto-ATPases. To permit the measurement of ATP secretion, several ecto-ATPase inhibitors were employed: N-ethylmaleimide, trifluoroperazine, etharinic acid, and the removal from external medium of Ca 2ϩ and Mg 2ϩ , the ions required for activation of ecto-ATPases (27). Only a minor reduction of ecto-ATPase activity was observed in cells treated with these inhibitors or in cells perifused with Ca 2ϩ /Mg 2ϩ -deficient medium.…”

Synthesis and Biological Activity of Novel 2-Thio Derivatives of ATP

“…The biological activity of the new substances has so far been judged from measurements of ectoenzyme-induced 32 (phosphatases, nucleotidases, phosphodiesterases) breakdown, studies of P 2 R ligand (agonist, antagonist) properties, second messenger formation 8 and resultant biological effects.…”