Dopaminergic stimulation of intestinal maltase activity in the freshwater fish Oligosarcus jenynsii

Intestinal disaccharidases are key determinants of carbohydrate assimilation in fish. Here, we characterized maltase and sucrase activity in juveniles of Oligosarcus jenynsii (Günther, 1864) and evaluated the modulation of maltase activity by dopamine. Maltase activity was detected across a broad pH (6.0–8.0) and temperature (4–45 °C) range and followed Michaelis–Menten kinetics (Km :1.22 mM), whereas sucrase activity was not detected. In vitro assays showed that dopamine significantly stimulated maltase activity in a concentration-dependent manner, with increases at 10-4 and 10-3 M. This stimulatory effect was not observed in the presence of the D1 receptor antagonist SCH-23390 or the D2 receptor antagonist chlorpromazine. These results demonstrate that intestinal maltase activity is responsive to dopaminergic stimulation under in vitro conditions and suggest the participation of dopaminergic pathways in this response. The physiological significance of this modulation in vivo remains to be established. These findings contribute to the understanding of the biochemical regulation of intestinal disaccharidases in a freshwater fish species.