Kinetics of Oxytocin and Deaminooxytocin Displacement from the Oxtr-Receptor Compartment in Rat Uterus Ex Vivo.

Kinetics of Oxytocin and Deaminooxytocin Displacement from the Oxtr-Receptor Compartment in Rat Uterus Ex Vivo. Biochem Pharmacol. 2018 Jan 05;: Authors: Pliska V, Jutz G Abstract The oil immersion method suggested earlier by Kalsner and Nickerson for analysing actions of sympathomimetic drugs in smooth muscle tissues was applied to isometric preparations of rat myometrium stimulated by oxytocin and deaminooxytocin. An exchange of the aqueous medium by mineral oil allows monitoring the displacement of the peptides from their receptor compartment in absence of free diffusion transport between tissue and organ medium. Exponential analysis of the data from the uterotonic decay phase allows several inferences to be drawn: 1) Transport rate constants (roughly equal for the two peptides) are higher than rate constants of (irreversible) elimination from the receptor compartment. 2) The response decay rate in the oil immersion phase is proportional solely to the peptide elimination and thus offers estimates of elimination rate constants. 3) Peptide elimination kinetics in the receptor compartment is only insignificantly influenced by the kinetics of ligand-receptor binding. 4) As expected, the elimination rate constant of deaminooxytocin is considerably lower than for oxytocin. The apparent concentration of receptors in the paracellular space of the myometrium ("apparent", since receptor molecules are embedded in the cell membrane and hence ...
Source: Biochemical Pharmacology - Category: Drugs & Pharmacology Authors: Tags: Biochem Pharmacol Source Type: research