Intracellular pH regulation in isolated hepatopancreas cells from the roman snail (Helix pomatia)

Abstract

The mechanisms of intracellular pH (pHi) regulation were studied in isolated hepatopancreas cells from the Roman snail, Helix pomatia. The relationship between intracellular and extracellular pH indicated that pHi is actively regulated in these cells. At least three pHiregulatory ion transporters were found to be present in these cells and to be responsible for the maintenance of pHi: an amiloride-sensitive Na þ /H þ exchanger, a 4-acetamido-4'-isothiocyanostilbene-2,2'disulfonic acid (SITS)-sensitive, presumably Na þ -dependent, ClÀ/HCO 3 À exchanger, and a bafilomycin-sensitive H þ -pump. Inhibition of one of these transporters alone did not affect steady state pHi, whereas incubation with amiloride and SITS in combination resulted in a significant intracellular acidification. Following the induction of intracellular acidosis by addition of the weak acid Na þ propionate, the Na þ /H þ exchanger was immediately activated leading to a rapid recovery of pHi towards the baseline level. Both the SITS-sensitive mechanism and the H þ -pump responded more slowly, but were of similar importance for pHi recovery. Measurement of pHi recovery from acidification in the three discernible types of hepatopancreas cells with a video fluorescence image system revealed slightly differing response patterns, the physiological significance of which remains to be determined.

Functional Involvement of Carbonic Anhydrase in the Lysosomal Response to Cadmium Exposure in Mytilus galloprovincialis Digestive Gland

“…This organ represents the key metabolic center in mollusks, being involved in energy storage, metabolic transformation, and trace element detoxification. Its cells are known to operate a fine regulation of intracellular pH (pHi), which is of crucial importance in cellular metabolism, by the activity of specific membrane transport systems, such as a Na + /H + exchanger, a Cl − / exchanger and a H + pump (Manzl et al, 2004 ). CA is known to play a vital role in cellular acid/base balance, being a key element for the functioning of acid/base-coupled membrane transporter.…”