title: Improved cardiac filling facilitates the postprandial elevation of stroke volume in Python regius.
abstract: To accommodate the pronounced metabolic response to digestion, pythons increase heart rate and elevate stroke volume, where the latter has been ascribed to a massive and fast cardiac hypertrophy. However, numerous recent studies show that heart mass rarely increases, even upon ingestion of large meals, and we therefore explored the possibility that a rise in mean circulatory filling pressure (MCFP) serves to elevate venous pressure and cardiac filling during digestion. To this end, we measured blood flows and pressures in anaesthetized Python regius The anaesthetized snakes exhibited the archetypal tachycardia as well as a rise in both venous pressure and MCFP that fully account for the approximate doubling of stroke volume. There was no rise in blood volume and the elevated MCFP must therefore stem from increased vascular tone, possibly by means of increased sympathetic tone on the veins. Furthermore, although both venous pressure and MCFP increased during volume loading, there was no evidence that postprandial hearts were endowed with an additional capacity to elevate stroke volume. In vitro measurements of force development of paced ventricular strips also failed to reveal signs of increased contractility, but the postprandial hearts had higher activities of cytochrome oxidase and pyruvate kinase, which probably serves to sustain the rise in cardiac work during digestion.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark sanneenok@gmail.com.
authors.forename: Sanne
authors.identifier: 0000-0003-4157-3617
authors.initials: S
authors.lastname: Enok
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, São Paulo 13565-905, Brazil.
authors.forename: Gabriella S P C
authors.initials: GS
authors.lastname: Leite
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, São Paulo 13565-905, Brazil.
authors.forename: Cléo A C
authors.initials: CA
authors.lastname: Leite
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Gesser
authors.affiliation: Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hedrick
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus 8000, Denmark.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wang
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001835:Body Weight; D017821:Boidae / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology; D003576:Electron Transport Complex IV / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology; D009929:Organ Size; D019518:Postprandial Period / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology*
chemical_list: D003576:Electron Transport Complex IV
keywords: Blood flow; Blood volume; Cardiac growth; Digestive regulation; Mean circulatory filling pressure; Venous tone