Effect of 17α-methyltestosterone (MT) on osmoregulatory responses and apoptosis in genetically improved farmed tilapia (GIFT), Oreochromis niloticus (L.)

Abstract

Androgenic compounds can affect osmoregulatory response and apoptosis in fish. In the present study, we exposed genetically improved farmed tilapia (GIFT) Oreochromis niloticus (L.) to 17α-methyltestosterone (MT, 0.5 and 5 mg/L) for 7, 14 and 21 days for understanding the phenomenon. The activities of Na⁺/K⁺ ATPase (NKA) and Ca²⁺/Mg²⁺ ATPase (CMA) were measured in the gill, kidney and intestine to evaluate the change in osmoregulation of GIFT, and genotoxicity was also detected. Results showed that organic NKA were significantly decreased in 5 mg/L MT exposure groups. The intestine NKA was significantly increased (0.5 mg/L MT). MT exposures increased the CMA of kidney and intestine (0.5 mg/L), together with gill CMA (5 mg/L MT). The results of genotoxicity assay showed gill atp1a1a and nkcc2 transcripts significantly increased, while intestine atp1a1a and fxyd7 transcripts revealed significant increases for MT exposure groups. Caspases proteins demonstrated significant increases at 7^th and 21^st day, and their transcripts were enhanced in 0.5 mg/L MT exposure groups. The results have evidently demonstrated that chronic exposure of MT could result in organic osmoregulatory response and hepatic apoptosis in GIFT O. niloticus.