Effects of orthovanadate on salt and water effluxes from the gills of seawater eels, Anguilla anguilla

The effects of vanadate on 45Ca exchange and enzyme secretion in the rat exocrine pancreas

The effects of vanadate on calcium homeostasis and enzyme secretion have been assessed in the incubated pancreas of young rats. Vanadate causes an acceleration of 45Ca efflux from pre-loaded uncinate glands; amylase release is reversibly increased for the duration of exposure to vanadate. Alkaline orthovanadate is most effective in eliciting these responses; its effects are greatly reduced at pH 7.4. However, changes in pH alone do not mimic these effects. Other vanadium oxides (meta-vanadate, vanadium pentoxide and vanadyl sulphate) are poor secretagogues. Alkaline ortho-, or meta-vanadate also causes an increased calcium uptake although this does not seem to be responsible for the observed secretory response. Vanadate is thought to stimulate pancreatic secretion by an effect on intracellular calcium store(s).

Transepithelial potential measurements in the isolated, perfused head of a marine teleost

The transepithelial potential (TEP) across the gills of a seawater teleost, the long-horned sculpin (Myoxocephalus octodecimspinosus), was measured both in vivo and utilizing an isolated, perfused head preparation (IPHP). The TEP of the IPHP was compared to that of the whole animal while in normal seawater and Na- or Cl-free seawater. The TEP or the IPHP in seawater was similar to that measured in vivo (+7.7 versus +7.2 mV, respectively). Na-free seawater induced a depolarization of both the IPHP and the intact fish, while Cl-free seawater hyperpolarized the TEP in vivo. The positive TEP of the sculpin, measured both in vivo and in vitro, is indicative of a transbranchial Na+ to Cl- permeability ratio greater than unity. The IPHP of the sculpin exhibits differential ion permeabilities similar to that of the whole animal. TEP comparisons described here should be applied to other IPHP systems now in use.