Cilnidipine: An L- and N-Type Blocker of Calcium Channels Ameliorating Renal Damage in Experimental Hypertensive Rats.

BACKGROUND

Cilnidipine is both an L-type and N-type calcium channel blocker (CCB). Cilnidipine suppresses hyperactivity in the renin-angiotensin system and sympathetic nervous system by blocking N-type calcium channels. We hypothesized that through its N-type calcium channel blockade, cilnidipine may reduce proteinuria and improve creatinine clearance in hypertensive rats.  Aim of the study: The current study was done to show the renal protective effect of cilnidipine on chronic hypertensive rats. Our primary objective is to develop a hypertensive rat model by giving L-NAME (NG-nitro-L-Arginine Methyl Ester Hydrochloride) and 4% sodium chloride (4% NaCl). High salt was given along with L-NAME because the combination of L-NAME and high salt intake leads to a synergistic effect on blood pressure. L-NAME impairs NO production, and high salt intake exacerbates this effect by promoting vasoconstriction and fluid retention. Our secondary objective is to evaluate the kidney damage measures, including recording of proteinuria, creatinine clearance, and urinary angiotensin II (Ang II) levels in hypertensive rats with or without cilnidipine treatment.

METHODS

Six groups of male Albino Wister rats (with six rats in each group) were created by a simple randomization technique. Rats were obtained from the animal house of our institution. Group 1 (control) received vehicle treatment; cilnidipine (2mg/kg/day by oral gavage) was given to Group 2; L-NAME (40mg/kg/day by oral gavage) was given to Group 3; Group 4 received L-NAME plus cilnidipine; Group 5 received L-NAME plus 4% NaCl (mixed with diet) treatment; Group 6 received L-NAME, 4% NaCl and cilnidipine. Creatinine excretion and urinary protein were assessed in a 24-hour urine sample. Serum urea and creatinine levels were also measured. Relative expression of serum and renal tissue ACE (angiotensin-converting enzyme) protein was done by Western blotting. Quantitative estimation of urinary and serum Ang II levels was done by enzyme-linked immunosorbent assay (ELISA). Kidney histopathological analysis was carried out.

RESULTS

In the renal tissue homogenate and serum of L-NAME and salt-induced hypertensive rats, we found elevated ACE and Ang II levels. We also observed a significant increase in proteinuria (4.65±0.29) compared to control (1.56±0.044) and a decrease in creatinine clearance (0.06±0.0019) compared to control (0.078±0.0044) in hypertensive rats. We observed that in treatment with cilnidipine (groups 4 and 6 rats), there were significant improvements in creatinine clearance (0.077±0.0027) (p < 0.05) and a significant decrease in proteinuria (3.38±0.24) ( < 005). In rats treated with cilnidipine, we also observed significantly decreased levels of Ang II in the urine and serum ( < 005) and a significantly decreased expression of ACE in the renal tissue and serum.

CONCLUSION

These results showed that in hypertensive experimental rats, cilnidipine, apart from its hypotensive actions, decreases proteinuria and urinary creatinine and Ang II levels. These actions of cilnidipine may be because of blocking N-type calcium channels. Therefore, cilnidipine dual L/N type CCB may act as a renoprotective drug and decrease glomerular damage. Further mechanistic studies using selective N-type channel blockers or knockout mice are needed to prove the findings.