Abstract

*Ahlam A. Alahmadi, PhD

ABSTRACT

Background: Nephrotoxicity is a common sequela of drug administration that has not been well investigated. Usnic acid (UA), a secondary metabolite of certain lichens, was reported to exert hepatotoxic and cardiotoxic effects. Objectives: The objective of the present work was to demonstrate the possible nephrotoxic effect of UA (100 and 300 mg/kg). Methodology: Thirty adult male rats (150–200 g) were sorted into the following groups: G1 (control rats) received 1% watery carboxymethyl cellulose CMC, G2 received 100 mg UA/kg, and G3 received 300 mg UA/kg; all treatments were administered for 8 weeks using oral gavage. Serum was collected for kidney function measurement, and kidney tissue was removed for ultrastructural studies. Results: Usnic acid at a low dose showed slight insignificant effects on both kidney function and ultrastructure. On the other hand, a high dose resulted in the irregularity and thickening of the glomerular membrane and podocyte footlets, and proximal tubules showed loss of microvilli and degenerative changes in basal infolding. Mitochondria showed swelling at a low dose and marked deformity at a high dose. Serum creatinine and blood urea nitrogen (BUN) levels were significantly increased, while there was minor alteration in blood electrolytes. Conclusion: UA at a low dose could be considered safe regarding kidney function and structure. If high doses are administered, the kidney function must be monitored or a renoprotective supplement must be combined with UA administration.