Fuel substrate utilization is highly regulated during cardiac development and with the onset of cardiac hypertrophy. Glucose and lactate are the predominant fuel substrates utilized during cardiac development. Postnatally, a switch occurs so that fatty acids become the chief energy substrate in the nonfed adult mammalian heart. A reversion back towards fetal energy metabolism occurs with the development of cardiac hypertrophy. To evaluate the role of this substrate preference switch in the development of cardiac hypertrophy, the molecular regulation directing these switches is being explored. Thus, we have begun by defining the temporal expression patterns of genes encoding key rate-controlling enzymes directing major fuel substrate metabolism during cardiac development, with pressure-overload-induced cardiac hypertrophy, and following antihypertensive therapy in spontaneously hypertensive rats. The genes encoding the fatty acid and adult enriched rate-controlling glycolytic enzymes are expressed at low levels in the fetal and neonatal rat heart. The genes encoding these enzymes are significantly and coordinately upregulated (> or = 70%) in adult rat hearts compared to the fetal expression patterns. A reciprocal and coordinate downregulation (> or = 40% reduction) of the fatty acid and adult enriched glycolytic enzyme encoding genes are observed with the induction of pressure-overload-induced hypertrophy in spontaneously hypertensive rats compared to Wistar-Furth normotensive control rats. Antihypertensive therapy with carvedilol, a vasodilating alpha- and beta-adrenoreceptor antagonist, attenuates this reversion of the metabolic gene expression pattern towards fetal levels compared to placebo-treated littermate controls. This coordinate developmental and hypertrophy-induced regulation of genes that encode enzymes controlling both fatty acid and glycolytic catabolic pathways in the heart implicates potential mutual/overlapping regulatory signaling proteins within their gene regulatory programs. These gene regulatory pathways need to be identified and modulated in order to characterize the functional role of fuel substrate metabolism in cardiac development and with the induction of cardiac hypertrophy.