Thermodynamic assessment of the use of alternative metabolic energy resources on work performance efficiency of spontaneous rat myometrium contractions

Abstract

Uterine smooth muscles (myometrium) are employed during labour to expel foetus (infant) out of the uterus. Exergy efficiency of the rat myometrium muscle contractions were assessed with the data collected in organ bath experiments in Krebs solutions. The major energy source, glucose, of the Krebs solution was substituted with sucrose, sodium pyruvate and calcium and lactate to assess the effect of the metabolic energy source on the exergy efficiency of work performance. Force versus time graphs were correlated with the work done during the contractions. Muscle contraction exergy efficiency was calculated as the ratio of work done by a muscle strip to the total exergy supplied. Exergy efficiency of the contractions was the highest, 36.7%, when lactate was the metabolic energy source and it was followed by 35.3% when pyruvate was the metabolic energy source. Exergy efficiencies of the cases with glucose and sucrose were 34.1% and 23.5%, respectively. The findings of this study may open way to further studies which may eventually help women give birth to babies with less pain by increasing exergy efficiency of the process.