title: Toborinone and olprinone, phosphodiesterase III inhibitors, inhibit human platelet aggregation due to the inhibition of both calcium release from intracellular stores and calcium entry.
abstract: OBJECTIVE
  We investigated the inhibitory effects of toborinone and olprinone on human platelet aggregation and calcium mobilization.Abstract Copyright:
  
  
  METHODS
  Washed human platelets were preincubated with toborinone or olprinone, then exposed to 0.015 U.ml-1 of thrombin. Aggregation curves were measured using an aggregometer. Effects of toborinone or olprinone on changes in intracellular calcium concentration ([Ca2+]i) were measured fluorometrically using fura-2 acetoxymethyl ester (fura-2). Levels of intracellular cyclic 3",5"-adenosine monophosphate concentration ([cAMP]i) were also measured, using enzyme-linked immunosorbent assay (ELISA) techniques.
  
  
  RESULTS
  The concentrations required to cause 50% inhibition of aggregation (IC50) induced by thrombin were 9.7 +/- 0.9 micro M for toborinone and 3.6 +/- 0.2 micro M for olprinone. Both drugs at IC50 significantly elevated [cAMP]i levels and significantly inhibited Ca2+ release from intracellular stores. Release of [Ca2+]i induced by thrombin was 272.9 +/- 87.1 nM, 153.3 +/- 28.7 nM, and 138.9 +/- 58.2 nM in the control, toborinone, and olprinone groups, respectively ( P < 0.02). Calcium influx through calcium channels in the plasma membrane was also suppressed by toborinone and olprinone.
  
  
  CONCLUSIONS
  Toborinone (9.7 micro M) and olprinone (3.6 micro M) inhibit human platelet aggregation, though these concentrations are higher than their therapeutic plasma concentrations. The inhibitory effects of both drugs are related to the inhibition of both Ca2+ release and Ca2+ entry through [cAMP]i elevation.
authors.affiliation: Department of Anesthesiology, Kyoto Prefectual University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kageyama
authors.forename: Toshiki
authors.initials: T
authors.lastname: Mizobe
authors.forename: Shinji
authors.initials: S
authors.lastname: Nozuchi
authors.forename: Noriko
authors.initials: N
authors.lastname: Hiramatsu
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Aoki
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011728:Pyridones / Q000494:pharmacology*; D015363:Quinolones / Q000494:pharmacology*; D013917:Thrombin / Q000494:pharmacology
chemical_list: D007093:Imidazoles; D010726:Phosphodiesterase Inhibitors; D010975:Platelet Aggregation Inhibitors; D011728:Pyridones; D015363:Quinolones; C077543:toborinone; C059498:olprinone; D000242:Cyclic AMP; D013917:Thrombin; D002118:Calcium