Regulatory Effect Of Ochratoxin A On Growth And Intestinal Structure Of Juvenile Grass Carp(Ctenopharyngodon Idella)

The present study was designed to determine the effects of dietary Ochratoxin A(OTA)on the growth,intestinal physical barrier and its potential mechanisms in juvenile grass carp(Ctenopharyngodon idella).A total of 1260 healthy juvenile grass carp(initial weight25.73±0.04g)were randomly distributed into seven groups of each three replicates fed seven diets containing graded OTA levels of(0,406,795,1209,1612,2003 and 2406 μg/kg)for60 days.After the feeding experiment,samples were taken to investigate the relevant indicators to explore the effect and mechanism of ochratoxin A on fish growth and intestinal structure.The results demonstrated that OTA could suppress the growth performance and intestinal development of juvenile grass carp.The decline of growth performance is partly associated with intestinal physical barrier.(1).OTA could reduce antioxidant ability by decreasing the m RNA and antioxidant enzymes in the intestine,which might be partly related to the inhibition of Nrf2/Keap1a(not Keap1b)signaling pathway;down-regulated the m RNA levels of antioxidant enzymes such as Cu Zn SOD,Mn SOD,CAT,GSTR,GSTP1,GSTP2,GSTO1,GSTO2,GR and Nrf2 in PI,MI and DI,thereby destroying intestinal cell structure(P<0.05).(2).Ochratoxin A could aggravate cell apoptosis through the mithochondrial apoptotic pathway,up-regulated the m RNA levels of caspase-2,caspase-3,caspase-7,caspase-8,caspase-9,Apaf-1,Bax,Fas L and JNK,down-regulated anti-apoptotic factors Bcl-2 and IAP m RNA levels(P<0.05)(not affect Mcl-1 m RNA);which might partly be regulated by activating JNK signaling pathway,resulting in the disruption of celluar structure integrity;(3).Ochratoxin A could impaire the TJs protein(ZO-1,occludin,claudinf,claudin-7a,JAM-A,claudin-11,claudin-15a)(except ZO-2b,claudin-b and claudin-3c)and adhesion junction-associated protein(E-cadherin,α-catenin,nectin and afadin)might be associated with the activation Rho A/ROCK/MLCK/NMⅡ signaling pathway.In this experiment,based on PWG and SGR,the maximum allowable level of OTA were 803.53 and 874.33 μg/kg diet,respectively.