AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 3 260-R268, Copyright © 1980 by American Physiological Society
Ion exchanges through respiratory and chloride cells in freshwater- and seawater-adapted teleosteans
J. P. Girard and P. Payan
The present study discusses the respective roles of the chloride and
respiratory cells in branchial ion exchange in freshwater- and
seawater-adapted teleosts. In the gill, two distinct epithelia are defined
according to their blood irrigation and cellular characteristics: the
primary lamellar epithelium containing mostly chloride cells is
functionally connected to the venous compartment; the secondary lamellar
epithelium consisting of respiratory cells is irrigated by the
arterioarterial circulation. The fundamental reorganization occurring in
the chloride cells during adaptation to seawater consists of the appearance
of leaky ultrastructure related to an increase in the ionic and
nonelectrolyte permeabilities of the primary lamellar epithelium. The
physiological functions of respiration, excretion, and the maintenance of
acid-base balance occur through the secondary lamellar epithelium both in
freshwater and seawater fish. The increase of the exchange diffusion across
the secondary lamellar epithelium on seawater adaptation is directly
related to the increase in the external salinity. The study of adrenergic
control in the teleost gill emphasizes the functional advantage to the fish
during adaptation to seawater of the anatomic separation of the
osmoregulatory primary lamellar epithelium.
