The physiological effects of 3,5',3'-triiodo-L-thyronine alone or combined with cortisol on cultured pavement cell epithelia from freshwater rainbow trout gills.
The effects of 3,5',3'-triiodo-L-thyronine (T3; 10 or 100 ng ml(-1)), alone or combined with cortisol (500 ng ml(-1)), on the physiological properties of cultured pavement cell epithelia from freshwater rainbow trout gills were assessed. T3 had dose-dependent effects on electrophysiological, biochemical, and ion transporting properties of cultured epithelia in both the absence and the presence of cortisol. These included reduced transepithelial resistance (TER), increased net Na(+) and Cl(-) movement (basolateral to apical) under asymmetrical culture conditions (freshwater apical/L15 media basolateral), and elevated Na(+)-K(+)-ATPase activity. However, paracellular permeability was elevated only in high-dose T3-treated preparations. In T3 + cortisol-treated epithelia, similar T3-induced alterations in TER, net Na(+) and Cl(-) movement, and paracellular permeability were observed, whereas the activity of Na(+)-K(+)-ATPase was further elevated. Under symmetrical culture conditions (L15 medium apical/L15 medium basolateral), T3 had no effect on transepithelial Na(+) and Cl(-) transport, which was passive. However, T3 + cortisol treatment resulted in active Na(+) extrusion (basolateral to apical). Under asymmetrical conditions, hormone treatment did not change the pattern of ion movement (active Na(+) extrusion, active Cl(-) uptake). These experiments demonstrate that cultured pavement cell epithelia from freshwater rainbow trout are T3-responsive and provide evidence for the direct action of T3 and the interaction of T3 and cortisol on the physiology of this preparation.
Kelly
S P
SP
Department of Biology, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.
Wood
C M
CM
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D017097:Electric Impedance; D004594:Electrophysiology; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D005880:Gills / Q000187:drug effects* / Q000502:physiology; D006854:Hydrocortisone / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D017686:Oncorhynchus mykiss; D011506:Proteins / Q000032:analysis; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014284:Triiodothyronine / Q000008:administration & dosage / Q000494:pharmacology*
D002712:Chlorides; D011506:Proteins; D014284:Triiodothyronine; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone