Factors influencing T3 transport into red blood cells of rainbow trout, Oncorhynchus mykiss
We exposed rainbow trout, Oncorhynchus mykiss, to various environmental conditions known to alter thyroid function in order to determine their effects on the in vitro carrier-mediated transport rate (J) of 3,5,3prime-triiodo-L-thyronine (T3) into red blood cells (RBC). Values for J (fmol T3 transported/(106 cells · min)) were (i) increased by assay temperature from 0 to 12°C but not from 12 to 21°C, (ii) unaltered by acclimation for 14 d at 5 or 12°C, (iii) depressed by a restricted food ration (0.5% of mean body mass/d) but unaltered by 14 d of fasting, (iv) depressed by a T3 challenge created by feeding T3-supplemented food (12 ppm T3) for 14 d, and (v) depressed 10 d after transport to our laboratory. We conclude that certain conditions that alter thyroid function also alter the rate of T3 transport into trout RBC, with possible consequences for exchange of T3 between plasma and RBC.