title: Pharmacokinetic-pharmacodynamic modeling of the effect of propofol on alpha 1-adrenoceptor-mediated positive inotropy in rat heart.
abstract: Since it is unclear whether and how propofol affects the alpha(1)-mediated inotropic response, we used a pharmacokinetic-pharmacodynamic modeling approach in isolated rat hearts to analyze the effect of propofol on receptor binding and signal transduction. In Langendorff rat hearts perfused with buffer containing 12.3 microM phenylephrine, 1.27 nmol doses of [(3)H]-prazosin were infused (over 1 min), in the absence and presence of propofol (28 microM). Simultaneous analysis of prazosin outflow concentration and inotropic response (left ventricular developed pressure) using an agonist-antagonist interaction model allowed to estimate receptor affinity, as well as the parameters of the operational model of agonism. Propofol significantly (P<0.05) increased the negative inotropic effect of prazosin. Modeling suggested that propofol increased the Hill coefficient, which determines the steepness of the stimulus-response curve for the positive inotropic effect of phenylephrine, from 1 to 2.6+/-0.1 and decreased the maximum achievable inotropic effect from 121.2+/-12 to 91.8+/-6 mmHg. Thus, propofol may attenuate the positive inotropic effect of alpha(1)-agonists by decreasing the transduction efficiency of alpha(1)-adrenergic receptor signaling primarily at lower receptor occupancy.
authors.affiliation: Section of Pharmacokinetics, Department of Pharmacology, Martin Luther University Halle-Wittenberg, Halle, Germany. michael.weiss@medizin.uni-halle.de
authors.forename: Michael
authors.initials: M
authors.lastname: Weiss
authors.forename: Rana
authors.initials: R
authors.lastname: Hassna
authors.forename: Pakawadee
authors.initials: P
authors.lastname: Sermsappasuk
authors.forename: Tobias
authors.initials: T
authors.lastname: Bednarek
mesh_terms: D000818:Animals; D002316:Cardiotonic Agents / Q000493:pharmacokinetics* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008954:Models, Biological; D008956:Models, Chemical; D015742:Propofol / Q000493:pharmacokinetics* / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*
chemical_list: D002316:Cardiotonic Agents; D018340:Receptors, Adrenergic, alpha-1; D015742:Propofol