Developmental changes in cardiac contractility in fetal and postnatal sheep: in vitro and in vivo
Anderson, P.A.; Glick, K.L.; Manring, A.; Crenshaw, C.
American Journal of Physiology 247(3 Pt 2): H371-H379
1984
ISSN/ISBN: 0002-9513 PMID: 6476131 Document Number: 226693
Developmental changes in contractility were sought in the fetal and postnatal sheep heart by using postextrasystolic potentiation and force, pressure and wall-motion measures. Two different preparations were used, isolated myocardium and the chronically instrumented lamb. In the isolated muscle, the following increased significantly with age: force of contraction, the maximum rate of rise of force, and postextrasystolic potentiation. In the intact heart prior to birth [period of study, 20 .+-. 4 (SD) days] heart rate (HR) fell significantly, and the following increased significantly: postextrasystolic potentiation [measured with the maximum rate of rise of left ventricular (LV) pressure (.ovrhdot.Pmax)], LV peak systolic pressure (LVP), end-diastolic dimension (EDD), end-systolic dimension (ESD), and aortic diastolic pressure. After birth, LVP, .ovrhdot.Pmax, HR, LVEDP, EDD and ESD increased and postextrasystolic potentiation fell. The latter fall was not found in vitro and probably demonstrates a transient change in contractility, related to hormonal or neural stimulation. Over the subsequent postnatal days (6-122 days), HR fell while potentiation, EDD and ESD increased significantly. Both in vitro and in vivo, the overall increase in postextrasystolic potentiation demonstrates a similar long-term change in contractility. The similarity of this change to that induced by mild hypertrophy suggests that development and mild hypertrophy alter myocardial contractility through a common mechanism.