Differences in metallothionein gene expression in primary cultures of rainbow trout hepatocytes and the RTH-149 cell line

Primary cultures of rainbow trout, Salmo gairdneri, hepatocytes were used to study the expression of metallothionein (MT) genes in response to steroid hormone treatment. The expression pattern was compared to that of an immortal cell line (RTH-149). MT mRNA accumulated in both cell cultures after exposure to zinc while 17 beta-oestradiol had no effect in either system. Treatment with cortisol and corticosterone resulted in a 2-fold increase of metallothionein mRNA levels in the primary cultures but had no effect in the RTH-149 cell culture. Primary cultures that were exposed to zinc or cortisol showed a high temporal correlation (r = 0.974) between MT mRNA and MT protein levels. The basal level expression was 3-4-fold higher in primary cultures than in RTH-149 cells. The present study demonstrates the inducibility of rainbow trout MT genes in response to glucocorticoids. It further indicates that primary cultures are to be preferred to immortal cell lines when investigating the inducibility of MT mRNA.