Sodium-glucose cotransporter 2 inhibitors (SGLT2i) represent a unique class of glucose-declining renal-targeted drugs. The SGLT2i Canagliflozin (CANA) is an anti-hyperglycemic drug that reduces various cardiovascular and renal outcomes in patients with type 2 diabetes mellitus. This study aimed to explore the potential effects of CANA on the isolated healthy adult rat hearts to show if CANA has positive inotropic or cardiac depressant effects via analyzing the amplitude and frequency of cardiac contractions. In isolated normal adult rat hearts, the effects of CANA on cardiac contractility were examined. In a dose-response curve, CANA led to a significant cardiac depressant effect in a dose-dependent manner. This cardiac depressant effect of CANA (10-6 M) was not prevented by atropine. However, this cardiac depressant effect was partially antagonized by both Isoproterenol (10-5 M) and Calcium chloride (10-6 M), suggesting beta-adrenoceptor and calcium channel blocking actions. In addition, the cardiac depressant effect of CANA (10-6 M) was mitigated in part by Nitric oxide synthase inhibitor, L-NAME, suggesting that its action probably depends to some extent on the accumulation of nitric oxide, which decreases the rise of intracellular Calcium. Data from this study demonstrate that CANA has a significant cardiac relaxant effect in isolated hearts of healthy adult rats by different possible mechanisms. This inhibitory effect on cardiac contractility may help improve the diastolic ventricular filling providing a therapeutic potential to help the other cardioprotective mechanisms of CANA in the prevention and treatment of heart failure.

KEY WORDS: Canagliflozin; Isoproterenol; L-NAME; Heart contractility; Rats.