In the present study, we examined whether standard chow (SDS versus Purina 5001; both low fat, high carbohydrate) and reductions in hexokinase (HK) II (wild-type versus HKII þ/2 mice) affect (1) growth parameters, (2) HK levels in cardiac and skeletal muscle and (3) low-flow cardiac ischaemia -reperfusion (IR) injury. Total HK activity and HKI and HKII expressions were determined, and low-flow IR injury was examined in isolated hearts subjected to 40 min 5% low-flow ischaemia and 120 min reperfusion. Standard chow, but not HKII reductions, significantly affected body weight, heart weight and cardiac hypertrophy. Both standard chow and reduced HKII diminished total cardiac and skeletal muscle HK activity. For the heart, the Purina chow-induced decrease in total HK activity was through decreases in HKI expression, whereas for skeletal muscle post-translational mechanisms are suggested. Both standard chow and reduced HKII demonstrated a non-significant trend for affecting cardiac IR damage. However, the low-flow ischaemia model was associated with mild sublethal injury only ( 1% cell death). In conclusion, standard chow affects body weight, heart weight and HK activity and HKI expression in the heart, without altering HKII expression. This implicates standard chow as an important factor in genomic, physiological research models and demonstrates that large differences in fat or carbohydrates in the diet are not necessary to affect growth. In a cardiac low-flow IR model, resulting in only mild injury, standard chow or reduced HKII does not significantly affect IR damage.Keywords: Nutrition, body weight, cardiology, pathology, perfused organ Laboratory Animals 2011; 45: 160-166. DOI: 10.1258/la.2011.010096To our knowledge, standard chow has received little attention in the field of animal experimentation. In contrast, much attention has been given to diets that differ largely in fat or carbohydrates, comparing e.g. low-fat with high-fat diets or low-carbohydrate with high-carbohydrate diets. However, often these diets not only differ in their fat or carbohydrate composition but also in many other components because diets are obtained from different suppliers. 1 -4 Uncertainty then exists as to whether observed effects can be ascribed to alterations in the main constituent (fat or carbohydrate) or to differences in the background standard chow used. Obviously, information is needed concerning the effects that standard chow per se may have on growth and other physiological parameters. We examined this question using wild-type (WT) and HK þ/2 mice. The HK þ/2 mice were shown to have a 50% reduction in hexokinase (HK) II activity in adipose, skeletal and heart tissues, without an effect on HKI activity.5 However, our own initial results with the HK þ/2 mice on HK activity did not show a significant difference between WT and HK þ/2 hearts. Interestingly, a recent study 1 demonstrated that difference in cardiac HKII content between WT and HK þ/2 hearts disappeared when animal nutrition was changed from low-fat to h...

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