Influence of temperature on the proliferative response of rainbow trout gonadal fibroblasts to cortisol and RU 486.

The rainbow trout gonadal cell line, RTG-2, which survives temperatures from 0 to 28°C and proliferates at 5 to 26°C, responded to cortisol from 28°C to 0°C by influencing [(3)H]-thymidine incorporation into DNA. Over the normal temperature range of rainbow trout, 10-22°C, cortisol inhibited [(3)H]-thymidine incorporation. The antiglucocorticoid RU 486 had no effect on [(3)H]-thymidine incorporation at these temperatures and blocked the response to cortisol. Another antiglucocorticoid RU 362 also had no effect but was less effective in blocking the cortisol response. During incubation at 28°C this inhibitory response to cortisol was detected inconsistently during the first 24 h but was observed consistently during the second 24 h. At 0°C, cortisol and RU 486 had no effect during short treatments, but a 60 h exposure to either steroid stimulated [(3)H]-thymidine incorporation over a 48 h labelling period. These results suggest that temperature shifts between 10-22°C, do not change the direction of a response to cortisol and support the use of the upper portion (20-22°C) of the temperature range for studies on salmonid cells in culture.