Carrageenin induced inflammation in Piaractus mesopotamicus (Osteichthyes: Characidae) cultured in Brazil

Abstract

The present work evaluated the acute inflammatory response induced by carrageenin (500 µg) injection into the swim bladder of pacu (Piaractus mesopotamicus) after consecutive stress of capture. Fish were subjected to air exposition of 30 seconds repeatedly at 60 minutes intervals over six hours. The cellular inflammatory component was evaluated six hours after either the carrageenan or the control (saline injection) by total and differential counts. Cortisol and glucose were analyzed each hour. In the inflammatory exudate, thrombocytes were the most frequently observed cells, followed by macrophages. A significant reduction of cortisol levels was observed after the third stress of capture, as well as an increase in glucose after the second stimulus of stress. Differential counts of circulating leucocytes and thrombocytes show increased percentage of special granulocytic cells and a significant neutrophilia in stressed fish. Non-stressed fish injected with carrageenin presented neutrophilia and lymphopenia. In the swim bladder, carrageenin provoked congestion, interstitial hemorrhage, dissociation of the collagen sheaf and inflammatory infiltrate.