Differentially expressed genes in response to cyadox in swine liver analyzed by DDRT-PCR.

Cyadox is a good antimicrobial growth-promoter of quinoxalines. However, the molecular mechanism of action remains unclear. A growth performance study and mRNA differential display reverse transcription polymerase chain reaction (DDRT-PCR) in combination with Northern dot-blot and reverse Northern dot-blot analysis were conducted to determine the differentially expressed genes in liver tissues of piglets after treatment with cyadox. Transcription levels of the differentially expressed genes were quantificated by realtime RT-PCR in porcine primary hepotocytes. Cyadox could significantly promote body weight of piglets via feed with average daily gain (ADG) improved by 24.7% and 64.8% in 100 and 500mg/kg group, compared with control. A total of eight differentially expressed genes were found, of which the expression levels of five genes had positive correlation with cyadox dose. One gene expression had a negative correlation with cyadox dose and it was a new gene. The other two genes were up-regulated by cyadox, but the expression quantity was invariably when the cyadox doses were increased. Among the up-regulated genes, one was transcriptional regulating factor, two were growth-related factors, one was involved in immune defense and immune-regulation and three might be involved in the maintenance of normal development. In primary cultured pig hepatocytes, cyadox treatment evoked a significant time-dependent effect of eight genes expression. The results suggest, at the transcriptional level in vitro and in vivo, that growth factor and metabolism may be associated with cyadox growth-promoting activity, whereas immune defense and immune-regulation could play major roles in prophylaxis of cyadox in piglets.