Myosin light-chain phosphorylation in diabetic cardiomyopathy in rats

• Published in: Metabolism, clinical and experimental clinical and experimental, 1997, Vol.46 (1), p.71-75
• Main Authors: Liu, Xueliang, Takeda, Nobuakira, Dhalla, Naranjan S.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - analysis; Animals; Associated diseases and complications; Biological and medical sciences; Blotting, Western; Diabetes Mellitus, Experimental - metabolism; Diabetes Mellitus, Experimental - physiopathology; Diabetes. Impaired glucose tolerance; Diabetic Angiopathies - metabolism; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Heart - physiology; Insulin - pharmacology; Male; Medical sciences; Myocardial Contraction - physiology; Myocardium - enzymology; Myocardium - metabolism; Myosin Light Chains - analysis; Myosin Light Chains - metabolism; Myosin Light Chains - physiology; Myosin-Light-Chain Kinase - analysis; Myosin-Light-Chain Kinase - metabolism; Myosin-Light-Chain Kinase - physiology; Phosphorylation; Rats; Rats, Sprague-Dawley; Streptozocin
• ISSN: 0026-0495; 1532-8600
• DOI: 10.1016/S0026-0495(97)90171-2

The regulatory myosin light chain (MLC) is phosphorylated in cardiac muscle by Ca 2+/calmodulin-dependent MLC kinase (MLCK) and is considered to play a modulatory role in the activation of myofibrillar adenosine triphosphatase (ATPase) and the process of force generation. Since the depression in cardiac contractile function in chronic diabetes is associated with a decrease in myofibrillar ATPase activity, we investigated changes in MLC phosphorylation in diabetic heart. Rats Were made diabetic by injecting streptozotocin (65 mg/kg intravenously); and the hearts were removed 8 weeks later; some 6-week diabetic animals were injected with insulin (3 U/d) for 2 weeks. Changes in the relative MLC and MLCK protein contents were measured by electrophoresis and immunoblot assay, whereas phosphorylated and unphosphorylated MLCs were separated on 10% acrylamide/urea gel and identified by Western blot. MLC and MLCK contents were decreased markedly (40% to 45%) and MLC phosphorylation was decreased significantly (30% to 45%) in the diabetic rat heart homogenate in comparison to control values. The changes in MLC and MLCK content in diabetic heart were partially reversible, whereas changes in MLC phosphorylation were normalized upon treatment with insulin. These results suggest that decreased protein contents of MLC and MLCK and phosPhorylation of MLC may contribute to the depression of cardiac myofibrillar ATPase activity and heart dysfunction in diabetic cardiomyopathy.