The prevalence of diabetes mellitus (DM) in the United Arab Emirates is among the highest in the world. Hearts of diabetic patients are frequently in a compromised condition. A variety of diastolic and systolic dysfunctions have been reported in patients with type 2 diabetes mellitus (T2DM). Although, several novel forms of intervention aiming at newly identified therapeutic targets are being developed for T2DM it is well established that physical exercise continues to be one of the most valuable forms of non-pharmacological therapy. An abundance of evidence exists for prescribing exercise therapy in the treatment of various diseases including metabolic syndrome-related disorders, heart and pulmonary diseases. Physical activity has been reported to influence several aspects of DM including blood glucose concentrations, insulin action and cardiovascular risk factors and long-term exercise has been repeatedly associated with lower rates of T2DM. The effects of DM and exercise training on expression of mRNA encoding cardiac muscle proteins and on ventricular myocyte contraction and intracellular Ca2+ transport in the adult Goto-Kakizaki (GK) type 2 diabetic rat was investigated. Experiments were performed in GK and control rats aged 10-11 months following 2-3 months of treadmill exercise training. Expression of mRNA was assessed in ventricular muscle with real-time RT-PCR. Shortening, intracellular free Ca2+ and L-type Ca2+ current were measured in ventricular myocytes with video edge detection, fluorescence photometry and whole cell patch clamp techniques. Non-fasting blood glucose was elevated in GK compared to age-matched controls and exercise slightly reduced blood glucose in control and more so in GK rats. Expression of mRNA encoding cardiac muscle, intercellular, cell membrane transport, calcium and potassium channel proteins were variously altered in GK and control rats and with exercise. Expression of Tpm2, Gja4, Atp1b1, Cacna1g, Cacnb2, Hcn2, Kcna3 and Kcne1 were up-regulated and Gja1, Kcnj2 and Kcnk3 were down-regulated in heart of GK rats compared to sedentary controls. Gja1, Cav3 and Kcnk3 were up-regulated and Hcn2 was down-regulated in hearts of exercise trained GK compared to sedentary GK controls. Amplitudes of shortening, Ca2+ transients and L-type Ca2+ current were not significantly altered in ventricular myocytes from GK rats compared to sedentary controls or by exercise training. Despite alterations in the profile of expression of mRNA encoding a variety of cardiac muscle proteins in the GK rat and as a result of exercise training, ventricular myocyte shortening and Ca2+ transport were generally well preserved in the adult GK diabetic rat heart.