Expression of Aquaporin 2, Aquaporin 3 and Aquaporin 4 in Renal Medulla of Bactrian Camel ( Camelus bactrianus )

Aquaporins (AQPs) are members of the aquaporin water channel family that play an important role in reabsorption of water from the renal tubular fluid to concentrate urine. Using immunohistochemical staining on paraffin sections, We studied expression ofAQP2, AQP3 and AQP4 in renal medulla of Bactrian camel (Camelus bactrianus). The renal medulla of cattle (Bos taurus) acted as the control. Compared with the control, strong expression of AQP2 was observed at the apical plasma membrane and intracellular vesicles, in both the outer medullary collecting duct (OMCD) and the inner medullary collecting duct (IMCD) of camel. Strong expression of AQP3 was observed at the basolateral plasma membrane of the IMCD of camel. Strong AQP4 expression, however, was observed at the basolateral plasma membrane in the OMCD of camel. Moreover, moderate AQP4 expression was detected in endothelium of capillary in medullary region of camels, whereas very weak/absent expression was detected in endothelium of capillary of cattle. We concluded that expression of AQP2, AQP3 and AQP4 in the camel kidney showed some differences from cattle in renal trans-epithelial water transport. It may enhance our better understanding of special water metabolism mechanisms that enable camels to survive in extreme environments. KEY WORDS: Bactrian camel (Camelus bactrianus); AQP2; AQP3; AQP4; Renal medulla. Las acuaporinas (AQP) son miembros de las proteinas de transporte que desempenan un papel importante en la reabsorcion de agua del liquido tubular renal para concentrar la orina. Estudiamos la expresion de AQP2, AQP3 y AQP4 en la medula renal del camello bactriano (Camelus bactrianus) usando tincion inmunohistoquimica en secciones de parafina. La medula renal del bovino (Bos taurus) se uso como control. En comparacion con el control, se observo una fuerte expresion de AQP2 en la membrana plasmatica apical y vesiculas intracelulares tanto en el conducto colector medular externo (CCME) como en el conducto colector medular interno (CCMI) del camello. Se observo una fuerte expresion de AQP3 en la membrana plasmatica basolateral del CCMI del camello. Tambien se observo una expresion fuerte de AQP4 en la membrana plasmatica basolateral en el CCME de camello. Ademas, se detecto una expresion moderada de AQP4 en el endotelio de los capilares en la region medular de los camellos, mientras que en el endotelio de los capilares del bovino se detecto una expresion muy debil. Concluimos que la expresion de AQP2,