Regulation of Intracellular pH in Rat Lactotrophs: Involvement of Anionic Exchangers*
Endocrinology. 1997-10-01; 138(10): 4191-4198
Read on PubMed
Garcia L(1), Boué-Grabot E, Garret M, Sartor P.
(1)Departement de Fisiologia, Facultad de Salud, Universidad del Valle, Cali, Columbia.
Regulation of the intracellular pH (pHi) of normal rat lactotrophs was studied. As this cell type, cultured with 10% FCS, can achieve a relatively alkaline pHi (7.3-7.5), we investigated the presence of a mechanism based on Cl-/HCO3- exchange. Using the pHi-sensitive probe SNARF-1 (seminaphtorodafluor) in its permeant form, SNARF-1/AM, we studied pHi recovery after acidic loading in individual cells with a microspectrofluorometric approach. We showed the involvement of anionic exchange in lactotroph cell pHi regulation. Acute CO2-bicarbonate cell acidic loading combined with external Cl- depletion induces the activation of a Cl-/HCO3- exchange. This exchange is 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid sensitive and corresponds to the type 3 anionic exchanger (AE3). However, after nigericin acidification, Na+/H+ exchange can also participate in recovery. In addition, incubation experiments strongly suggest that a 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid-insensitive anionic exchanger (type 2 anionic exchanger or AE2) is present in rat lactotrophs. The presence and involvement of carbonic anhydrase in pHi regulation have been demonstrated. Finally, using Northern blot and reverse transcription-PCR techniques, messenger RNAs for both AE2 and AE3 were identified in anterior pituitary cell extracts. We concluded that in normal rat lactotrophs, pHi regulation is achieved by a complex system in which Cl-/HCO3- exchange has a