Coronary artery disease causes an increase in glutamate uptake and alanine output by the heart. We assessed the effects of acute myocardial ischemia on alanine and glutamate exchange and ammonia production in 10 anesthetized open-chest domestic swine (46.9 +/- 0.7 kg). Coronary blood flow was controlled through an extracorporal perfusion circuit. After a nonischemic control period (aerobic) the blood flow in the left anterior descending coronary artery was reduced by 60%. Arterial and anterior interventricular venous samples where drawn before and during 35 min of ischemia. Subendocardial blood flow, measured using radiolabeled microspheres, decreased from 1.27 +/- 0.16 to 0.25 +/- 0.09 (ml/g)/min, and left-ventricular wall-thickening fell to 47% of aerobic values. Ischemia resulted in a significant increase in the rate of glucose uptake (p less than 0.05) and a switch to net lactate production (p less than 0.01). Ischemia did not affect the rates of alanine output (-0.9 +/- 1.0 vs. -0.3 +/- 0.3 mumol/min) or glutamate uptake (-0.4 +/- 1.1 vs. 0.3 +/- 0.6 mumol/min), but did increase the venous-arterial difference for ammonia (-4.1 +/- 4.1 to 52.7 +/- 5.5 microM, p less than 0.0001) and the ammonia output (-0.33 +/- 0.24 to 1.34 +/- 0.14 mumol/min, p less than 0.0001). In conclusion, acute ischemia did not stimulate greater alanine output or glutamate uptake. However, acute ischemia did cause an increase in anaerobic glycolysis rate and ammonia output, which reflects a profound disruption in myocardial energy metabolism.

Background: Congenital heart defects (CHDs) encompass a large numbers of cardiovascular malformations, and remain the major cause of infant mortality among all types of birth defects. However, molecular mechanisms underlying CHDs remain elusive, largely owning to the complexity of the diseases and lack of animal models that can reproduce the pathophysiological conditions in a laboratory setting. The hyperpolarization-activated, cyclic nucleotide-gated cation channels (HCN) are responsible for generating spontaneous pacemaker activities in cardiac and central nervous systems. These channels are also detected in other cell types such as ventricular myocytes. HCN currents recorded from neonatal cells have an activation threshold of -70 mV while those recorded from adult cells are activated at -110 mV. This difference indicates that HCN activity might be important in early development. However, roles of HCN channels in cardiogenesis and development are not fully understood. Methods and Results: We created a HCN2 conditional knockout (HCN2KO) model in which the full-length HCN2 was disrupted. Two KO lines were subsequently derived from this model. The first line was weaned by 21 days and they all died by 4-5 wks of age. Maternal ultrasound study revealed that these KO mice developed fetal arrhythmia and had an underdeveloped left side in their hearts. The second line was able to live on under our special diet/care. These mice displayed a slower growth rate (1.1±0.2 g/wk) and lower body weight (15.1±2.0 g) relative to their age-matched WT controls (2.2±0.1 g/wk and 27.5±1.5 g; n=9-10, p<0.05). Echocardiography and tissue staining data suggested that KO hearts had laterality defects compared to their size-matched WT controls. The survived KO mice were able to maintain cardiac function by developing much thicker anterior and posterior walls to sustain blood-pumping (n=6, p<0.05). Electrocardiographic results indicated that the average heart rate recorded from KO mice was ~100 bpm slower than their age-matched WT controls (n=5-6, p<0.05). Conclusions: These novel findings indicate that HCN2 is indispensable in mouse cardiogenesis and development. Our KO models are therefore innovative platforms for future CHD research.

Moderate to extreme premature birth is associated with a 17-fold higher risk of heart failure in childhood through early adulthood, with the right ventricle disproportionately affected. However, preclinical models to study heart failure mechanisms are poorly defined. Here, we utilized varying durations of postnatal hyperoxia exposure, a common model for bronchopulmonary dysplasia, to characterize the preterm heart phenotype. Methods: Pups from timed-pregnant Sprague Dawley rats were randomized to normoxia or hyperoxia (F I O 2 0.85-0.95