Active NaCl absorption across split lamellae of posterior gills of the chinese crab Eriocheir sinensis: stimulation by eyestalk extract.
Split lamellae of the posterior gills of freshwater-adapted Chinese crabs (Eriocheir sinensis) were mounted in a modified Ussing-type chamber, and active and electrogenic absorption of Na(+) and Cl(-) were measured as positive (I(Na)) or negative (I(Cl)) short-circuit currents. Haemolymph-side addition of eyestalk extract stimulated I(Cl) by increasing both the transcellular Cl(-) conductance and the electromotive force for Cl(-) absorption. The effect was dose-dependent. Boiling the eyestalk extract did not change its effectiveness. The stimulating factor passed through dialysis tubing, indicating that it has a molecular mass of less than 2 kDa. R(p)cAMPS, a blocker of protein kinase A, reduced the stimulated I(Cl). Eyestalk extract stimulated I(Na) by increasing the transcellular Na(+) conductance at constant electromotive force. Amiloride-induced current-noise analysis revealed that stimulation of I(Na) was accompanied by an increase in the apparent number of open apical Na(+) channels at a slightly reduced single-channel current. In addition to the electrophysiological experiments, whole gills were perfused in the presence and in the absence of putative transport stimulators, and the specific activities of the V-ATPase and the Na(+)/K(+)-ATPase were measured. Eyestalk extract, theophylline or dibutyryl-cyclic AMP stimulated the activity of the V-ATPase, whereas the activity of the Na(+)/K(+)-ATPase was unaffected. The simultaneous presence of R(p)cAMPS prevented the stimulation of V-ATPase by eyestalk extract or theophylline.
Onken
H
H
Institut für Tierphysiologie, Freie Universität Berlin, Grunewaldstrasse 34, D-12165 Berlin, Germany. onkenh@ffclrp.usp.br
Schöbel
A
A
Kraft
J
J
Putzenlechner
M
M
D000042:Absorption; D000818:Animals; D003386:Brachyura / Q000502:physiology*; D003994:Bucladesine / Q000494:pharmacology; D018118:Chloride Channels / Q000502:physiology; D004553:Electric Conductivity; D005123:Eye; D005880:Gills / Q000502:physiology*; D006358:Hot Temperature; D008970:Molecular Weight; D006180:Proton-Translocating ATPases / Q000378:metabolism; D015222:Sodium Channels / Q000502:physiology; D012965:Sodium Chloride / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013806:Theophylline / Q000494:pharmacology; D014020:Tissue Extracts / Q000494:pharmacology*; D025262:Vacuolar Proton-Translocating ATPases
D018118:Chloride Channels; D015222:Sodium Channels; D014020:Tissue Extracts; D012965:Sodium Chloride; D003994:Bucladesine; D013806:Theophylline; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase