Maternal Nutrient Restriction Alters Ca²⁺ Handling Properties and Contractile Function of Isolated Left Ventricle Bundles in Male But Not Female Juvenile Rats

<div><p>Intrauterine growth restriction (IUGR), defined as a birth weight below the 10th centile, may be caused by maternal undernutrition, with evidence that IUGR offspring have an increased risk of cardiovascular disease (CVD) in adulthood. Calcium ions (Ca²⁺) are an integral messenger for several steps associated with excitation-contraction coupling (ECC); the cascade of events from the initiation of an action potential at the surface membrane, to contraction of the cardiomyocyte. Any changes in Ca²⁺ storage and release from the sarcoplasmic reticulum (SR), or sensitivity of the contractile apparatus to Ca²⁺ may underlie the mechanism linking IUGR to an increased risk of CVD. This study aimed to explore the effects of maternal nutrient restriction on cardiac function, including Ca²⁺ handling by the SR and force development by the contractile apparatus. Juvenile Long Evans hooded rats born to Control (C) and nutrient restricted (NR) dams were anaesthetized for collection of the heart at 10–12 weeks of age. Left ventricular bundles from male NR offspring displayed increased maximum Ca²⁺-activated force, and decreased protein content of troponin I (cTnI) compared to C males. Furthermore, male NR offspring showed a reduction in rate of rise of the caffeine-induced Ca²⁺ force response and a decrease in the protein content of ryanodine receptor (RYR2). These physiological and biochemical findings observed in males were not evident in female offspring. These findings illustrate a sex-specific effect of maternal NR on cardiac development, and also highlight a possible mechanism for the development of hypertension and hypertrophy in male NR offspring.</p>