Dapagliflozin reduces the amplitude of shortening and Ca²⁺ transient in ventricular myocytes from streptozotocin-induced diabetic rats

In the management of type 2 diabetes mellitus, Dapagliflozin (DAPA) is a newly introduced selective sodium-glucose co-transporter 2 inhibitor which promotes renal glucose excretion. Little is known about the effects of DAPA on the electromechanical function of the heart. This study investigated the effects of DAPA on ventricular myocyte shortening and intracellular Ca²⁺ transport in streptozotocin (STZ)-induced diabetic rats. Shortening, Ca²⁺ transients, myofilament sensitivity to Ca²⁺ and sarcoplasmic reticulum Ca²⁺, and intracellular Ca²⁺ current were measured in isolated rats ventricular myocytes by video edge detection, fluorescence photometry, and whole-cell patch-clamp techniques. Diabetes was characterized in STZ-treated rats by a fourfold increase in blood glucose (440 ± 25 mg/dl, n = 21) compared to Controls (98 ± 2 mg/dl, n = 19). DAPA reduced the amplitude of shortening in Control (76.68 ± 2.28 %, n = 37) and STZ (76.58 ± 1.89 %, n = 42) ventricular myocytes, and reduced the amplitude of the Ca²⁺ transients in Control and STZ ventricular myocytes with greater effects in STZ (71.45 ± 5.35 %, n = 16) myocytes compared to Controls (92.01 ± 2.72 %, n = 17). Myofilament sensitivity to Ca²⁺ and sarcoplasmic reticulum Ca²⁺ were not significantly altered by DAPA in either STZ or Control myocytes. L-type Ca²⁺ current was reduced in STZ myocytes compared to Controls and was further reduced by DAPA. In conclusion, alterations in the mechanism(s) of Ca²⁺ transport may partly underlie the negative inotropic effects of DAPA in ventricular myocytes from STZ-treated and Control rats.