• Denis J Crankshaw, Jennifer M Walsh, and John J Morrison.
• Department of Obstetrics and Gynaecology, National University of Ireland Galway, Galway, Ireland. Electronic address: cranksha@mcmaster.ca.
• Life Sci. 2014 Oct 22; 116 (1): 25-30.

AimsMethyl palmitate is thought to cause relaxation in vascular smooth muscle by opening voltage-activated potassium channels. We have tested the hypothesis that methyl palmitate, a putative regulator from perivascular fat, is an inhibitor of the contractility of human pregnant myometrium and that its effects might partially explain the higher incidence of dysfunctional labor in obese women compared to those with normal body mass indices.Main MethodsStrips of myometrium obtained with informed consent from women undergoing elective cesarean section at term were mounted in organ baths. Strips stimulated with oxytocin (1nM) or KCl (30mM) were exposed to cumulatively increasing concentrations of methyl palmitate up to 10μM. Similar strips were exposed to cumulative addition of the potassium channel blockers 4-aminopyridine and tetraethylammonium. The contractility of the strips was monitored and analyzed using conventional methods.Key FindingsMethyl palmitate failed to inhibit oxytocin- or KCl-induced contractions over the concentration range tested. In fact, it exerted a slight excitatory effect in the presence of KCl, though not in the presence of oxytocin. The contractility of naïve strips was unaltered by exposure to 1μM methyl palmitate. Both 4-aminopyridine and tetraethylammonium produced concentration-dependent contractions of human pregnant myometrium providing pharmacological evidence for the presence of voltage-activated potassium channels in this preparation.SignificanceOur findings do not support the hypothesis that methyl palmitate is an inhibitor of human pregnant myometrial contractility. Alternate hypotheses must be pursued to explain the higher incidence of dysfunctional labor in obese women.Copyright © 2014 Elsevier Inc. All rights reserved.

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