AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 9-15, Copyright © 1989 by American Physiological Society
Ventricular function and fatty acid metabolism in neonatal piglet heart
R. J. Ascuitto, N. T. Ross-Ascuitto, V. Chen and S. E. Downing
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510.
Studies in which subcellular systems were used suggest that neonatal
myocardium has a sharply limited capacity to metabolize fatty acids. The
relationship of these findings to the intact heart was tested on piglets, 8
h to 12 days of age. Left ventricular (LV) performance, O2 consumption
(MVO2), and fatty acid (FA) uptake and oxidation were measured. Hearts were
perfused at 70 cmH2O pressure with buffer containing 2% bovine serum
albumin, insulin (100 microU/ml), 5 mM glucose, and 1.5 mM lactate.
14C-labeled palmitate was added (net FA, 0.5 mM). Washed erythrocytes were
used to assure adequate O2 delivery. LV end-diastolic pressure (EDP) was
controlled with a fluid-filled balloon. FA oxidation was estimated by
measuring 14CO2 production. Hearts less than 24 h (group I, n = 6), those
approximately 3 days (group II, n = 5), and those 6-12 days of age (group
III, n = 10) were compared. Measurements at a low EDP (2-4 cmH2O) and at a
higher EDP (7-9 cmH2O) were compared. At the low EDP, rates of FA oxidation
for groups I-III averaged 30.0 +/- 3.0, 31.4 +/- 2.9, and 50.2 +/- 2.6
nmol.min-1.g-1, respectively. These values increased to 43.8 +/- 3.7, 42.6
+/- 2.5, and 63.8 +/- 4.0 nmol.min-1.g-1, respectively, at the higher EDP
level (P less than 0.01 for each group). Thus within a few hours of birth,
pig hearts are able to oxidize long-chain FA, and the rate of oxidation is
linked to mechanical function. However, both the oxidation rate and the
percentage of MVO2 accounted for by FA oxidation are greater in older
hearts.
