Fig. 4. Effects of organic osmolytes or colchicine on Ostf mRNA expression levels in primary gill cell culture. Primary gill cells were grown overnight in the isotonic medium (320 mOsmol l^–1) and were then subjected to hypertonic treatment (NaCl, 500 mOsmol l^–1) with the addition of (A) either 5 mmol l^–1 of inositol, betaine or taurine or (B) 100 µmol l^–1 colchicine. After 6 h of treatment, total RNA was extracted and was reverse transcribed for real-time PCR assay. Note that the cotreatment of the hypertonicity-exposed cells with the organic osmolytes or colchicine abolished the induced Ostf mRNA expression. ^*P<0.05 compared with the control cells. The results were obtained from five independent experiments.