Effect of cilnidipine as an antihypertensive agent on two forms (L-NAME and L-NAME+4%NaCl) of hypertension in rats.

Abstract

Background: A calcium channel blocker (CCB) of the fourth generation, cilnidipine, is dihydropyridine. It is inhibiting calcium channels of both the L- and N-type. Vascular smooth muscle contains L-type calcium channels, while presynaptic nerve terminals contain N-type calcium channels. Vasodilating effects from cilnidipine are slow-acting and persistent. Very few research studies have been done to clarify how N-type calcium channel blockers affect hypertensive rats whose nitric oxide production has been suppressed. Aim and objectives: The purpose of our study was to show protective effect of cilnidipine on L-NAME or L-NAME plus salt induced experimental hypertension rats. Objectives of our study are to assess cardiovascular hemodynamic parameters like heart rate, mean arterial blood pressure, symapathovagal balance by heart rate variability analysis (HRV), systemic and renal oxidative stress (serum and kidney tissue MDA), renin angiotensin system activity (Kidney and serum VEGF, NOS3 and ACE protein expression and serum and urinary Ang II level) in N G -nitro-L-arginine methyl ester hydrochloride (L-NAME) induced hypertensive rat model. Further we investigated (24hour protein excretion, Creatinine clearance, Renal fibrosis/glomerulosclerosis) as markers of renal injury in response to L-NAME and L NAME plus salt induced hypertensive rats with or without cilnidipine treatment. Material and methods: 36 male Albino Wister rats were collected from institutional animal house (six rats in each group). Group1 vehicle treated (control), group2 cilnidipine (2mg/kg body weight/day) treated, group3 treated with L-NAME (40 mg/kg body weight/day), group4 treated with L-NAME and cilnidipine, group 5 treated with L-NAME and 4% sodium chloride (4% NaCl), group 6 L-NAME, cilnidipine and salt treated. All experimental animals underwent gravimetry and after28-day percentage of body weight gain calculation was made. Estimates were made for haematological variables such as Haemoglobin (g/dl), RBC count (million cells/mm3), and haematocrit (percentage). HRV analysis was performed to evaluate changes in the cardiovascular autonomic system, Heart rate (HR) and blood pressure (BP) were monitored every week for 28 days as examples of cardiovascular hemodynamic events. Blood pressure was recorded by non-invasive tail cuff method. Oxidative stress was assessed by estimating serum and kidney tissue MDA levels. Serum and kidney tissue nitric oxide levels were measured as nitrosative stress markers. Proteinuria and creatinine clearance were measured. kidney function parameters (serum urea and creatinine) were also measured. Serum eNOS, Ang II and urinary Ang II levels were quantitatively measured by ELISA technique. Relative expression of serum and kidney tissue NOS3, ACE and VEGF protein levels were done by Western Blotting. Histopathological examination of the Aorta and kidney tissue was done. Results: Lower percentage body weight gain was seen after L-NAME administration, and changes in the sympathovagal balance and sympathetic overactivity were discovered by HRV analysis. Heart rate was lower and mean arterial pressure was higher in Hypertensive rats. There is increase in serum and kidney tissue oxidative stress. Marked decreased in serum and kidney tissue NO and NOS3 levels. There is increased serum and kidney tissue VEGF and ACE protein expression. There is increase in serum and urinary Ang II levels. We also observed proteinuria and decreased creatinine clearance in NO deficient and salt supplemented hypertensive rats. Cilnidipine treatment was able to 1) reduce MAP and Heart rate 2) reduce sympathetic activity 3) decrease serum and kidney tissue oxidative stress 4) increase