Salidroside contributes to reducing blood pressure and alleviating cerebrovascular contractile activity in diabetic Goto-Kakizaki Rats by inhibition of L-type calcium channel in smooth muscle cells

Background: Vascular disease is a common and often severe complication in diabetes mellitus. Hyperglycemia and hypertension are considered to be two of the leading risk factors for vascular complications in diabetic patients. However, few pharmacologic agents could provide a combinational therapy for controlling hyperglycemia and blood pressure in diabetic patients at the same time. Salidroside (SAL) is the major active ingredient derived from Rhodiola. Recently, it has been reported that SAL have an obvious hypoglycemic effect in diabetes and show a beneficial activity in diabetic vascular dysfunction. However, it remains unknown whether or not SAL treatment could directly reduce blood pressure in diabetes. Furthermore, it is not clear what is the molecular mechanism underlying the vascular protection of SAL treatment in diabetes. Methods: Male diabetic Goto-Kakizaki (GK) and non-diabetic control Wistar-Kyoto (WKY) rats were administrated with different dosages of SAL (50, 100 and 200 mg/kg/day) for 4 weeks. Contractile responsiveness of cerebral artery to KCl or 5-HT was investigated by Pressure Myograph System. The activity of Ca-L channel was investigated by recording whole-cell currents, assessing the expressions of Ca-L channel alpha(1C)-subunit and its downstream kinase, MLCK, at protein or mRNA levels. Results: We showed that administration of 100 mg/kg/day SAL for 4 weeks not only lowered blood glucose, but also reduced blood pressure and alleviated cerebrovascular contractile activity in diabetic GK rats, which suggested that SAL treatment may provide a combinational therapy for lowering blood glucose and reducing blood pressure in diabetes at the same time. Furthermore, SAL treatment markedly inhibited the function and expression of Ca-L channel in cerebral VSMCs isolated from diabetic GK rats or when exposed to hyperglycemia condition, which may be the underlying mechanism responsible for the vascular protection of SAL in diabetes. Conclusions: The present study provided evidences that SAL contributes to reducing blood pressure and alleviating cerebrovascular contractile activity in diabetic GK rats by inhibition of Ca-L channel in smooth muscle cells, which may provide a novel approach to treat vascular complications in diabetic patients.