Histological and immunohistochemical study of the effect of orlistat on the exocrine pancreas of adult female albino rat

Introduction: Orlistat is considered to be a safe and effective drug to treat obesity by decreasing the absorption of digested fat. However, many cases of orlistat-induced pancreatitis were reported. Aim of the study:This study was carried out to study the effect of orlistat on the histological structure of the exocrine part of the pancreas, and to evaluate the possibility of recovery after its withdrawal. Materials and methods:Forty-eight adult female albino rats were divided into; group I (control), group II (each animal received 32 mg orlistat orally once daily for 8 weeks) and group III (recovery), which received the same dose of orlistat and was left without any treatment for another 8 weeks. The pancreas from each animal was dissected out and processed for histological (light microscopic and electron microscopic) study. The result of immunohistochemical (inducible nitric oxide synthase) stain was statically analyzed. Results:Sections of orlistat-treated rats showed variable disturbance of normal architecture of the pancreatic acini, congestion of blood vessels, and widening of the spaces between the acini. The acinar cells showed vacuolation of their cytoplasm. Immunostaining of inducible nitric oxide synthase revealed significant increase in the reaction in group II. Ultrastructure examination showed dilated rough endoplasmic reticulum, destroyed mitochondria, and dissolution of zymogene granules in some acinar cells. These findings were improved after stoppage of the drug. Conclusion:Orlistat has a harmful effect on pancreatic acini. Thus, it must be taken under medical observation.