The Parotoid Gland Secretion of Bufonids Inhibits the Activity of the Multidrug Resistance Target Pdr5p from Yeast Plasma Membranes

Abstract

Aims: Considering the well known biological effects of secretion of cutaneous glands in anurans and that Pdr5p belongs to the ATB-Binding Cassette (ABC) superfamily of membrane transporters, which efflux a large variety of xenobiotic compounds, and play an important role in the multidrug resistance (MDR), the parotoid gland of two bufonids were used in order to evaluate their secretion activity on Pdr5p of plasma membranes of the yeast Saccharomyces cerevisiae as a potential inhibitor of MDR. Place and Duration of Study: Laboratory of Integrative Histology and Laboratory of Microbian Biochemistry, Federal University of Rio de Janeiro, between September 2009 and October 2011. Methodology: Five male bufonids of Rhinella icterica and of R. ornata were used, and the parotoid gland secretion was obtained after manual gland comprehension and by dissection. ATPase assays as well as SDS-PAGE were performed, besides immunohistochemical analysis at light microscopy. Results: Pdr5p ATPase activity was inhibited when the crude extract was obtained by manual compression from the parotoid gland in contrast to the isolated intake of the large granular alveoli, which showed no enzymatic activity. Moreover, the Pgp expression in acinar cells of both mixed and small granular glands as well as in a myoepithelial cells was visualized by immunohistochemistry, suggesting its participation in tissue defense against toxic compounds. Conclusion: The inhibitory effect of crude extract obtained by manual comprehension was detected, while the isolated intake showed no effect on the Pdr5p ATPase activity. Both bufonid represent an important source of biomolecules, opening new perspectives of research on natural products.