AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 3 346-R352, Copyright © 1985 by American Physiological Society
Electrolyte transport by alkaline gland of little skate Raja erinacea
P. L. Smith
Transepithelial flux studies and conventional intracellular microelectrode
measurements were employed to examine the mechanisms of ion transport by
the alkaline gland of the male skate, Raja erinacea. These studies reveal
that the transepithelial potential is 6.9 +/- 0.6 mV, lumen reference, and
that the transepithelial resistance is 140 omega . cm2. The short-circuit
current across this epithelium is entirely accounted for by net secretion
of Cl, whereas transepithelial active transport of Na does not appear to be
present in this tissue. Cl secretion and/or short-circuit current are
reduced by serosal furosemide and abolished when the bathing solution Na is
replaced with choline or when ouabain is added to the serosal bathing
solution. Intracellular microelectrode studies reveal that the apical
membrane potential is -43 mV, cell interior negative to the mucosal bathing
solution. The transepithelial resistance in these tissues was 103 +/- 12
omega . cm2 and the apparent fractional resistance, i.e., the ratio of the
change in apical membrane potential to the change in transepithelial
potential produced by passing current across the epithelium was 0.39 +/-
0.09. Ion substitution experiments demonstrated that the apical membrane is
dominated by a large Cl conductance while the basolateral membrane contains
a barium-sensitive potassium conductance. These results suggest that the
mechanism of Cl secretion by the alkaline gland is similar to the mechanism
described for a variety of Cl secretory epithelia.
