The electrical, structural, and permeability properties of primary cultures of rainbow trout gill cells on permeable supports were examined after 6 days of growth in culture medium, followed by prolonged (48 hr) apical exposure to fresh water. Permeability to the paracellular marker polyethylene glycol-4000 (PEG) increased significantly over 48 hr, indicating that paracellular permeability increased continuously throughout the freshwater exposure. The significant increases measured in the net Na+ and Cl- fluxes were attributed primarily to the opening up of the paracellular pathway. The elevated transepithelial resistance characteristic of the cultured branchial epithelium with fresh water present on the apical surface gradually declined during prolonged exposure, and the decrease (increase in conductance) was greater than that expected on the basis of the increasing paracellular permeability. At any given time, PEG permeability was linearly related to conductance, but PEG permeability per unit conductance decreased significantly over 48 hr. These results are suggestive of an increase in transcellular permeability in addition to that in paracellular permeability. Since transcellular permeability appears to decrease on first exposure to fresh water, the elevated permeability during prolonged exposure was interpreted as a reopening of the transcellular pathway. A morphological examination revealed evidence of damage to the superficial cell layer of the multilayered culture following 48 hr of apical freshwater exposure, accounting at least in part for the physiological changes observed. Hormonal supplementation of the basal culture medium was examined as a means of enhancing adaptation to apical fresh water. The inclusion of teleost prolactin (200 ng/L) or teleost growth hormone (200 ng/L) in the basal culture medium had no effect on either the initial values or the pattern of changes during prolonged exposure for TER, PEG permeability, and net ion fluxes.
|Original language||English (US)|
|Number of pages||15|
|Journal||Journal of Experimental Zoology|
|State||Published - Aug 15 1998|
ASJC Scopus subject areas
- Animal Science and Zoology