AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 3 160-R164, Copyright © 1980 by American Physiological Society
Gill arch of the mullet, Mugil cephalus III. Rate of response to salinity change
F. E. Hossler
The rate of response of gill filament epithelium to salinity changes was
determined by scanning electron microscopy and biochemical techniques. An
increase in Na-K-ATPase content, as measured by [3H]ouabain binding, was
detected at 3 h and continued to about 24 h after mullet were transferred
from a salinity of 1-4.5%. In contrast, filaments from mullet transferred
to freshwater exhibited a decrease in ouabain-binding sites. Similarly,
scanning electron microscopy revealed that ultrastructural modifications
occurred in epithelial pores of the filament surface in response to
salinity changes. These modifications, which included changes in pore
diameter and depth and in the number of cellular extensions in the pore's
interior, were evident as early as 6 h and were mostly completed by 24 h
after the salinity change. Because epithelial pores likely represent apical
pits of chloride cells and because the Na-K-ATPase is localized within
chloride cells, the present observations likely represent different
manifestations of the very rapid response of chloride cells to osmotic
stress, and indicate the close association of structure with function.
