Intracellular voltage recordings in the opercular epithelium of Fundus heteroclitus

Abstract

Opercular epithelial cells of Fundus heteroclitus were investigated using conventional microelectrodes. The area of interest was the cells lining the inside of the opercular epithelium closest to the gill arches, an area with a high density of chloride cells. Only one cell type could be discerned from the values of 60 opercular cells measured with the opercular epithelium in open circuit conditions. A mean apical voltage of -18.0 +/- 0.6 mV was observed with intracellular values ranging from -10 to -30 mV. The predicted intracellular chloride content was 59 mM/liter. Apical fractional resistance (faR) was 0.78 +/- 0.02. The intracellular potential measurements were typically difficult to maintain for extended periods (longer than 3 min). The opercular cells depolarize with serosal isoproterenol treatment (10(-6) M) corresponding to the increase in opercular transepithelial potential. The opercular cell apical fR decreased with isoproterenol treatment. These data indicate the observed opercular cells were involved in opercular chloride transport.

Regulation of Cl− secretion in seawater fish (Dicentrarchus labrax) gill respiratory cells in primary culture

“…Similar results on Isc have been found in the opercular membrane (Mendelsohn et al 1981;Eriksson et al 1985;Marshall et al 1993) and in fish skin (Marshall & Bern, 1980). In our study, addition of isoproterenol also caused a stimulation of Vt, a result found in the operculum (Zadunaisky et al 1988). The present investigation establishes the existence of â_adrenergic receptors in gill respiratory-like cells of a marine fish.…”

Cystic fibrosis transmembrane conductance regulator in the gills of the climbing perch, Anabas testudineus, is involved in both hypoosmotic regulation during seawater acclimation and active ammonia excretion during ammonia exposure

“…The permeation of Clis not driven by, but actually results in, the apical electrical potential which is different from the basolateral electrical potential, and the difference between these two potentials defines the transepithelial electrical potential across the branchial epithelium. However, the only one measurement on the electrical potential across the apical membrane of MRC in the literature reported a value of *18 mV (inside negative) for the short-circuited opercular epithelium of seawater adapted F. heteroclitus (Zadunaisky et al 1988;Wright 1991). If such an electrical potential was to be established by passive Cl -movement, the intracellular Clconcentration must be close to 270 mmol l -1 (Wright 1991), which is highly improbable due to the presence of negatively charged intracellular proteins.…”