Permeability and Morphology of a Culture Branchial Epithelium from the Rainbow Trout Prolonged Apical Exposure to Freshwater
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 media, followed by prolonged (48h) apical exposure to freshwater. Permeability to the paracellular marker polyethylene glycol-4000 (PEG) increased signifcantly over 48 hours, indicating that paracellular permeability increased continuosly throughout the freshwater exposure. The significant increases measured in the 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 freshwater present on the apical surface gradually declined during prolonged exposure, and the decrease 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 hours. These results are suggestive of an increase in transcellular permeability in addition to that in paracellular permeability. As transcellular permeability appears to decrease upon first exposure to freshwater, the elevated permeability during prolonged exposure was interpreted as a re-opening of the transcellular pathway. A morphological examination revealed evidence of damage to the superficial cell layer of the multilayered culture following 48 hours of apical freshwater exposure, accounting at least in part for the physiological changes observed. Hormonal supplementation of the basel culture medium was examined as means of enhancing adaption to apical freshwater. The inclusion of teleost prolactin or teleost growth hormone in the basel 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.
Bibliographic Reference: Article: Journal of Zoology, 281 (1998), 531-545
Record Number: 199910709 / Last updated on: 1999-05-14
Original language: en
Available languages: en