AlF 4 − and vanadate stimulate chloride secretion in rabbit colon by a Ca2+-dependent mechanism

Stripped rabbit descending colon mucosae were studied in vitro in modified Ussing chambers to determine the effects of AlF ₄ ^– and vanadate on Cl^– transport. Serosal additions of AlF ₄ ^– and vanadate increase short-circuit current (I _SC) and tissue conductance, while luminal addition of the agents is ineffective. Addition of aluminium potentiates the effect of NaF on I _SC. AlF ₄ ^– and vanadate increase serosal-to-mucosal flux of ³⁶Cl without affecting mucosal-to-serosal flux. The effects of these agents on I _SC are markedly inhibited by serosal addition of bumetanide and depend on the presence of Na⁺ in the serosal bathing solution. The effects of AlF ₄ ^– and vanadate on I _SC are dependent on the presence of Ca²⁺ in the bathing solution, and are completely inhibited by indomethacin, but the effect of forskolin is not affected by the removal of Ca²⁺ from the bathing solution and the addition of indomethacin. AlF ₄ ^– and vanadate significantly increase the level of inositol phosphate metabolites. The results indicate that AlF ₄ ^– and vanadate increase Cl^– secretion in the rabbit colon via an increase in prostaglandin synthesis which is mediated by the increase of intracellular Ca²⁺ concentrations.