Identification of Band 3-like Proteins and Cl-/HCO3- Exchange in Isolated Cardiomyocytes

The identification of the protein that exerts the function of Cl-/HCO3- exchange is still unresolved in cardiac tissue. We have addressed this issue by using a multiple technical approach. Western blotting analysis with an antibody raised against human erythroid whole band 3 protein, the so-called protein that mediates the Cl-/HCO3- exchange in erythrocytes, showed that adult cardiomyocytes expressed two proteins immunologically related to the erythroid band 3. These proteins migrated in SDS-polyacrylamide gel electrophoresis with apparent molecular masses of 80 and 120 kDa. They were specifically found in the membrane but not in the cytosolic or the myofibril fractions of adult cardiomyocytes. Confocal microscopy further indicated that the immunostained proteins were mainly located at the sarcolemma and along T-tubules, typical membrane structures of adult cardiomyocytes. Using an antibody raised against a cardiac amino-terminal domain of rat AE3, we found that the 120-kDa protein is the translation product of the AE3 gene specifically expressed in heart and brain. Using an antiserum raised against a specific domain of mouse erythroid band 3 (AE1), which is not shared by AE3, we showed that the 80-kDa protein is likely to be a truncated translation product of the AE1 gene. Microinjection of the anti-human erythroid whole band 3 antibody into single isolated cardiac cells significantly inhibited the Cl-/HCO3- exchange activity. Furthermore, the anti-AE1 antibody strongly decreased the efficiency of 4,4′-diisothiocyanatostilbene-2,2′-disulfonate to inhibit the ionic exchange. We thus suggest that the 80-kDa or both the 80- and the 120-kDa proteins immunologically related to the erythroid band 3 protein perform the anionic exchange in rat cardiomyocytes. The identification of the protein that exerts the function of Cl-/HCO3- exchange is still unresolved in cardiac tissue. We have addressed this issue by using a multiple technical approach. Western blotting analysis with an antibody raised against human erythroid whole band 3 protein, the so-called protein that mediates the Cl-/HCO3- exchange in erythrocytes, showed that adult cardiomyocytes expressed two proteins immunologically related to the erythroid band 3. These proteins migrated in SDS-polyacrylamide gel electrophoresis with apparent molecular masses of 80 and 120 kDa. They were specifically found in the membrane but not in the cytosolic or the myofibril fractions of adult cardiomyocytes. Confocal microscopy further indicated that the immunostained proteins were mainly located at the sarcolemma and along T-tubules, typical membrane structures of adult cardiomyocytes. Using an antibody raised against a cardiac amino-terminal domain of rat AE3, we found that the 120-kDa protein is the translation product of the AE3 gene specifically expressed in heart and brain. Using an antiserum raised against a specific domain of mouse erythroid band 3 (AE1), which is not shared by AE3, we showed that the 80-kDa protein is likely to be a truncated translation product of the AE1 gene. Microinjection of the anti-human erythroid whole band 3 antibody into single isolated cardiac cells significantly inhibited the Cl-/HCO3- exchange activity. Furthermore, the anti-AE1 antibody strongly decreased the efficiency of 4,4′-diisothiocyanatostilbene-2,2′-disulfonate to inhibit the ionic exchange. We thus suggest that the 80-kDa or both the 80- and the 120-kDa proteins immunologically related to the erythroid band 3 protein perform the anionic exchange in rat cardiomyocytes. INTRODUCTIONIntracellular pH (pHi) modulates various cellular events including metabolism, ionic conductances, Ca2+ homeostasis, and cell division. In cardiac muscle, both Ca2+ homeostasis and Ca2+ sensitivity of myofilaments, which closely regulate contractility, are affected by changes in pHi(1Orchard C.H. Kentish J.C. Am. J. Physiol. 1990; 258: C967-C981Crossref PubMed Google Scholar). pHi also modulates gap junction conductances and in turn cardiac conduction(2White R.L. Doeller J.E. Verselis V.K. Wittenberg B.A. J. Gen. Physiol. 1990; 95: 1061-1075Crossref PubMed Scopus (104) Google Scholar). A fine regulation of pHi is thus required to maintain cardiac function. To such an end, the cardiac cell possesses membrane ionic transporters sensitive to intracellular pH. Under acid loads, a Na+/H+ antiport is mainly activated to extrude protons from the myocyte(3Piwnica-Worms D. Lieberman M. Am. J. Physiol. 1983; 244: C422-C428Crossref PubMed Google Scholar, 4Frelin C. Vigne P. Lazdunski M. J. Biol. Chem. 1984; 259: 8880-8885Abstract Full Text PDF PubMed Google Scholar). A Na+- and HCO3--dependent transporter was also recently reported to participate in pHiregulation from acidosis(5Liu S. Piwnica-Worms D. Lieberman M. J. Gen. Physiol. 1990; 96: 1247-1269Crossref PubMed Scopus (75) Google Scholar, 6Lagadic-Gossman D. Buckler K.J. Vaughan-Jones R.D. J. Physiol. (Lond.). 1992; 458: 361-384Crossref Scopus (217) Google Scholar). In contrast, a rise in pHiactivates a Na+-independent Cl-/HCO3- exchanger, which operates as a HCO3- extruder(7Vaughan-Jones R.D. J. Physiol. (Lond.). 1979; 295: 111-137Crossref Scopus (117) Google Scholar). Numerous studies have been devoted to the Na+/H+ antiport in many cell types including cardiomyocytes. More specifically, the cDNA encoding the cardiac Na+/H+ antiport was recently cloned, and the protein responsible for the cationic exchange was immunologically identified(8Fliegel L. Sardet C. Pouyssegur J. Barr A. FEBSLett. 1991; 279: 25-29Crossref PubMed Scopus (64) Google Scholar). Although under physiological conditions the Cl-/HCO3- exchanger is the only ionic transporter able to alleviate alkaline loads in cardiac tissue, much less data are available in regard to the protein responsible for cardiac anionic exchange.The best characterized Cl-/HCO3- exchanger in tissues so is the band 3 The protein is responsible for the of HCO3- by the of intracellular The anionic HCO3- and The of membrane proteins and a molecular of PubMed Scopus Google Scholar, 3 Scholar). which with band were in various cells but not in cardiac J.C. S. A. 1983; PubMed Scopus Google Scholar, D. J. Biol. 1984; Scholar). proteins were to perform the ionic exchange function in S. D. J. Biol. Chem. Full Text PDF PubMed Google and Full Text PDF PubMed Scopus Google Scholar, J. S. A. 1991; PubMed Scopus Google Scholar). Numerous studies using molecular that band proteins to a of proteins in They have been into the acid and AE3 the of the gene that Physiol. 1991; PubMed Scopus Google Scholar). More specifically, the AE1 gene the erythroid band 3 as as a truncated of the in J. Biol. Chem. Full Text PDF PubMed Google Scholar). AE1 were also recently found in J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). The are mainly expressed in and the AE3 are the in and Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). AE3 cDNA the was recently from a rat heart cDNA is to AE3 cDNA for and a of J. Biol. Chem. 1992; Full Text PDF PubMed Google blotting studies to the of the in whole is not the translation are in cardiomyocytes and proteins are anionic this was to band proteins expressed in cardiac cells and to proteins the anionic exchange function. of and Physiol. 1991; PubMed Scopus Google Scholar). AE1 and AE3, in the J. Biol. Chem. 1991; Full Text PDF PubMed Google a to be of the a antibody raised against the erythroid band 3 was to band proteins in cardiac tissue. proteins of apparent molecular masses of 80 and 120 were found in adult The two proteins were only in the membrane from adult rat isolated cardiac a of Confocal microscopy of immunostained adult rat showed the of the proteins at the sarcolemma and Using an antiserum specific to AE1 and an antibody specific to AE3, the 80- and 120-kDa proteins were characterized as of AE1 and AE3 Furthermore, that or both proteins perform the anionic exchange in cardiac of 3 and of of were to C. PubMed Scopus Google from human band 3 protein was to the of and C. A. Google Scholar). band 3 was from membrane by The of the protein was by a and from a The protein was by cytosolic of human band 3 was isolated from the by the of and J. Biol. Chem. Full Text PDF PubMed Google Scholar). the were of of proteins by with of acid at and with pH The were at for and with of for at The were and the was the of a The cytosolic of human band 3 was against at pH and in The was by SDS-polyacrylamide gel and the of the cytosolic of human band 3 was in the with J. Biol. Chem. 1983; 258: Full Text PDF PubMed Google of of the were in SDS-polyacrylamide gel The and to the cytosolic of human band 3 and whole band were by and from the The were in and against and were for the of with as by Western blotting of human erythroid The were with for The were at with were and the The and of the were by The were at by with to to The were and at of an AE3 antibody was raised against a to the J. Biol. Chem. 1992; Full Text PDF PubMed Google amino-terminal domain of rat cardiac AE3 which is not shared by The was to and to were for the of of as by Western blotting of cardiac The were with with 3 was the and The antibody was by the to The antibody was and at of and were from to PubMed Scopus Google and from two adult were from and the were for in a to The were into and using a in a pH and The were for at to the The were and with electrophoresis rat cells were as M. A. Am. J. Physiol. Google with the the from were and in a for and with of with the heart was and into The was a The cells were and for at Ca2+ of the was by to The at were at in to pH and and for at of and from the adult rat cardiac the was in a to pH and with and The was at for and at for The was with electrophoresis In to the cells were and in electrophoresis the cells were in a and using a The was at for The was as the cytosolic The was in the with The was for and was at for The was as the membrane The myofibril was with the and in cytosolic and membrane fractions were with electrophoresis to Western to further the of band proteins in the the was in to pH and in ionic with for at The was at for The was and the with to Western and Western was to PubMed Scopus Google Scholar). were or SDS-polyacrylamide gel electrophoresis to PubMed Scopus Google Scholar). proteins were to a membrane to J. S. A. 1979; PubMed Scopus Google Scholar). of were for at with in pH with the were at with the antibody or antiserum anti-human band AE1 cardiac AE3 the were with the antibody to or to for at In the the were and with for at were using as for or the to the The were for or for the was of and in Confocal the cells were to They were with and for at with in The cells were in in for at with and with for at in and by in with and for at the cells were at with the antibody erythroid whole band 3 or in the cells with were for at in the of or at a of and by antibody was to The were in immunostained cells were in microscopy using a an were using an and an were for and Confocal was to a of was to the to the with a of and a of were using a a and of pH was in single isolated cells to and with the as M. J. Physiol. (Lond.). 1991; Scopus Google Scholar). such the cells were in a 120 and to pH at In the to the Cl-/HCO3- exchanger, of the were in the of to the Na+/H+ antiport activity. pHi was in using the M. J. Physiol. (Lond.). 1991; Scopus Google of Ca2+ and the cells to were with by for in intracellular Ca2+ and further in cytosolic Ca2+ M. J. 1991; PubMed Scopus Google Scholar). the cardiomyocytes were at in the of and thus further cell In we that of cells not Cl-/HCO3- activity. was the pHi and not to the Cl-/HCO3- exchanger as by the of in the ionic exchange and cells were to the of an and were in only The anti-human erythroid band 3 antibody as as were to a of in the and to pH with The were a and the by into a of the anti-human whole erythroid band 3 antibody or the a of to the by were using a The antibody or was from the by the into the to for of the indicated that the cell been cells were to for at at the are as were by are at was from was from was from and antibody were from were from and were from blotting analysis with an anti-human whole erythroid band 3 antibody was to the of band proteins in from adult The human band 3 by the antibody as a band of the The antibody also with rat band 3 in rat further that in adult cardiac the antibody strongly with two proteins that migrated with apparent molecular masses of 80 and 120 kDa. were the anti-human erythroid band 3 antibody was in the of of human band 3 The antibody also with the 80 and 120 proteins in a whole cell from adult rat isolated cardiac cells in and or in isolated cells in electrophoresis suggest that the 80 band is not a product of the 120-kDa addressed the proteins were of two the AE1 and AE3 were found in whole J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). The of such proteins was thus in as a that the AE3 proteins apparent molecular masses of 80 and 120 were by the antibody in this as the band at 120 to be in in cardiac the 80 band was Using an antiserum raised against a specific domain of mouse AE1 J. S. D. S. A. PubMed Scopus Google which is not shared by rat AE3, Western blotting of cardiac membrane proteins mainly a 80 band and two of molecular and In contrast, an antibody raised against the amino-terminal of human erythroid band 3 not with protein in cardiac whole cell or membrane rat band 3 antibody raised against a cardiac specific amino-terminal domain of rat AE3 shared by mouse strongly with the 120-kDa protein but not with the 80-kDa in cardiac membrane from isolated cardiomyocytes. The 120-kDa band was the was with the antibody in the of the which as The antibody not protein in human or rat the membrane proteins were in the gel and the was and with both the AE3 and the anti-human erythroid band 3 the protein by the antibody migrated to the apparent molecular as the molecular protein by the band 3 the data suggest that the 80- and 120-kDa proteins are by two The 120-kDa protein is to the of the cardiac AE3 cDNA J. Biol. Chem. 1992; Full Text PDF PubMed Google Scholar). is by an antibody specifically raised against an amino-terminal domain of rat cardiac is also much expressed in in the specific was not found in J. Biol. Chem. 1990; Full Text PDF PubMed Google is still that the 120-kDa protein from AE3 from the cardiac or that was also by J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). we that the 120-kDa found in cardiac cells is the translation product of the cardiac AE3 the 80-kDa protein was also by an antiserum raised against a specific domain of which is not shared by J. Biol. Chem. 1992; Full Text PDF PubMed Google Scholar, J. S. D. S. A. PubMed Scopus Google Scholar, PubMed Scopus Google we suggest that this protein is a translation product of of the AE1 expressed in J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). We found a of this protein in which is in with the in of with AE1 J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). The as to the 80-kDa is the amino-terminal truncated of the erythroid band 3 as the in J. Biol. Chem. Full Text PDF PubMed Google is to The antibody raised against the amino-terminal of human erythroid band 3 not with of the proteins in rat cardiac an is with the of an amino-terminal truncated of erythroid band 3 in cardiac we still the that such a of was to the of the amino-terminal of band A. S. S. M. J. 1992; PubMed Scopus Google characterized two band proteins in cardiac we at and myofibril fractions were from isolated cardiomyocytes. Western blotting of the membrane proteins the of both the 80- and 120-kDa of proteins was in the cytosolic or the myofibril We also to band proteins from and of by a ionic not and microscopy were to further the specific of band proteins in adult rat isolated cardiomyocytes. 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Biol. 1983; PubMed Scopus Google Scholar). is to that the exchanger was recently found to be also along the sarcolemma and J. Biol. 1992; PubMed Scopus Google Scholar). a of ionic be in cardiac cells for an of the exchange the cell and the The of band proteins for a regulation of pH and the of HCO3- by the of The of band proteins in the that pH or the protein an function for the or the to the membrane as in Physiol. 1990; PubMed Scopus Google of immunostained The were immunostained by the anti-human whole band 3 antibody or an antibody were by a or The cell in was with only the The were from at an of in the The anti-human whole band 3 antibody the antibody to the The antibody of the band proteins in immunostained cells in of a cell with both the anti-human whole band 3 antibody by a antibody and an antibody by a The by the band 3 antibody to the that are not by the Confocal of the cell as in A immunostained with both the anti-human whole band 3 and the In A and the were from the of the at an of single of a cell with the band 3 The the of the cell of Western blotting analysis that both the 80- and 120-kDa proteins to the be that or both proteins an ionic exchange function in cardiac PubMed Scopus Google have recently reported that in an gene is the anionic exchange function is not To the proteins in Western blotting and cell perform the Cl-/HCO3- we the of both the anti-human erythroid whole band 3 antibody and AE1 antiserum anionic exchange in single cardiomyocytes. The of from a and to the of HCO3- into the cell the of the Cl-/HCO3- The of the an the cell to pHi The of the cells for at in the of the band 3 antibody not the of pHi changes by and In contrast, of the band 3 antibody into the single cardiomyocytes inhibited the Cl-/HCO3- exchange activity. The of by was in the cells with the anti-human erythroid whole band 3 antibody with the of the cells with at the as the 3 antibody in the cells with the anti-human erythroid whole band 3 the of by was also The in that the of the anionic exchange was a in the cells with the 3 antibody with the cells with or the be that the was the exchanger in physiological as further in cells that were not able to pHi The anionic and AE3 J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar, Am. J. Physiol. PubMed Google a regulation by intracellular or HCO3- in a physiological pHi AE1 such a regulation only at alkaline or M. J. Gen. Physiol. PubMed Scopus Google Scholar, J. J. Physiol. (Lond.). Scopus (117) Google Scholar). The that cells that were with the human erythroid band 3 antibody to pHi suggest that the of the antibody to of the exchanger such a pHi was in a physiological this also at under AE3 as an anionic to the that at in the of the membrane the of the ionic of which only at the of the membrane but not at the for 3 Scholar). The of the antibody to the exchanger and in turn such a further to the of a exchange by band proteins in isolated cardiac of the band 3 antibody into single cardiac cells the Cl-/HCO3- exchange by of pHi single cells with of or with of anti-human erythroid whole band 3 antibody with or as pHi was in using an intracellular of that the cell in a of the as in or band 3 The of the anionic exchange was from both the and the The were from the of pHi pH in or and the were expressed as an intracellular of M. A. Am. J. Physiol. Google Scholar). are expressed as significantly from the of pHi by be to the Cl-/HCO3- exchanger the cells were for of at in the of of showed that such a an of the exchange that was the was or be that the of such an of the exchanger to be in a exchanger J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar). the at a the was and the exchange the was in the cell using a of Under this of the anionic exchange was in the The was at and required be that been reported to both AE1 and AE3 but not J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar, A. PubMed Scopus Google Scholar). Although the cellular the sensitivity of the exchanger to the of the that AE1 and AE3 are expressed and that or both as an ionic exchanger in cardiac the AE1 antiserum was raised against a to a domain from the we the of the antiserum the efficiency to the anionic exchange. of the cells for at in the of the antiserum by a strongly to the the of to the as The of the ionic exchange was at and was required to the anionic exchange activity. a in of the exchanger was not the cells were with a The ionic exchange was not affected the cardiomyocytes were for at in the of the anti-AE1 which a of the We thus suggest that AE1 in the anionic exchange of cardiac the cells with the anti-AE1 antibody the of cells were for at in the of of The was and the Cl-/HCO3- exchange was as in from the of the of The were and a in the of the AE1 antiserum or of a are expressed as of at cells for using technical including Western microscopy of immunostained and pHi we have in cardiac cells two proteins immunologically related to the erythroid band 3. These proteins in SDS-polyacrylamide gel electrophoresis with apparent molecular masses of 80 and 120 kDa. They are found only in the membrane from isolated cells and to be in single Furthermore, of the anti-human erythroid whole band 3 antibody significantly the Cl-/HCO3- exchange in isolated which strongly that or both proteins the function of anionic exchange. the of the by a mouse anti-AE1 antibody strongly that not of the anionic exchange in isolated adult rat cardiomyocytes is by the 80-kDa physiological of to the regulation of the Cl-/HCO3- exchanger in the We reported that both the and the the anionic exchange in cardiac M. J. Physiol. (Lond.). 1991; Scopus Google Scholar, M. M. J. Physiol. (Lond.). Scholar). The identification of band proteins in heart to that the of the a of the 80 band protein M. J. Physiol. (Lond.). Scholar). and in the is by M. M. PubMed Scopus Google Scholar). is J. Biol. Chem. 1992; Full Text PDF PubMed Google is likely that the 80-kDa protein be by to the that AE1 be the exchanger is by in cardiac are required to the of AE1 and AE3 in cardiac protein as an anionic exchanger and the as an protein or both both To this we are the of into the cardiomyocytes of cardiac AE3 the ionic exchange activity. Furthermore, the of to the of AE1 or AE3 also be to into the function of expressed in cardiomyocytes. INTRODUCTIONIntracellular pH (pHi) modulates various cellular events including metabolism, ionic conductances, Ca2+ homeostasis, and cell division. In cardiac muscle, both Ca2+ homeostasis and Ca2+ sensitivity of myofilaments, which closely regulate contractility, are affected by changes in pHi(1Orchard C.H. Kentish J.C. Am. J. Physiol. 1990; 258: C967-C981Crossref PubMed Google Scholar). pHi also modulates gap junction conductances and in turn cardiac conduction(2White R.L. Doeller J.E. Verselis V.K. Wittenberg B.A. J. Gen. Physiol. 1990; 95: 1061-1075Crossref PubMed Scopus (104) Google Scholar). A fine regulation of pHi is thus required to maintain cardiac function. To such an end, the cardiac cell possesses membrane ionic transporters sensitive to intracellular pH. Under acid loads, a Na+/H+ antiport is mainly activated to extrude protons from the myocyte(3Piwnica-Worms D. Lieberman M. Am. J. Physiol. 1983; 244: C422-C428Crossref PubMed Google Scholar, 4Frelin C. Vigne P. Lazdunski M. J. Biol. Chem. 1984; 259: 8880-8885Abstract Full Text PDF PubMed Google Scholar). A Na+- and HCO3--dependent transporter was also recently reported to participate in pHiregulation from acidosis(5Liu S. Piwnica-Worms D. Lieberman M. J. Gen. Physiol. 1990; 96: 1247-1269Crossref PubMed Scopus (75) Google Scholar, 6Lagadic-Gossman D. Buckler K.J. Vaughan-Jones R.D. J. Physiol. (Lond.). 1992; 458: 361-384Crossref Scopus (217) Google Scholar). In contrast, a rise in pHiactivates a Na+-independent Cl-/HCO3- exchanger, which operates as a HCO3- extruder(7Vaughan-Jones R.D. J. Physiol. (Lond.). 1979; 295: 111-137Crossref Scopus (117) Google Scholar). Numerous studies have been devoted to the Na+/H+ antiport in many cell types including cardiomyocytes. More specifically, the cDNA encoding the cardiac Na+/H+ antiport was recently cloned, and the protein responsible for the cationic exchange was immunologically identified(8Fliegel L. Sardet C. Pouyssegur J. Barr A. FEBSLett. 1991; 279: 25-29Crossref PubMed Scopus (64) Google Scholar). Although under physiological conditions the Cl-/HCO3- exchanger is the only ionic transporter able to alleviate alkaline loads in cardiac tissue, much less data are available in regard to the protein responsible for cardiac anionic exchange.The best characterized Cl-/HCO3- exchanger in tissues so is the band 3 The protein is responsible for the of HCO3- by the of intracellular The anionic HCO3- and The of membrane proteins and a molecular of PubMed Scopus Google Scholar, 3 Scholar). which with band were in various cells but not in cardiac J.C. S. A. 1983; PubMed Scopus Google Scholar, D. J. Biol. 1984; Scholar). proteins were to perform the ionic exchange function in S. D. J. Biol. Chem. Full Text PDF PubMed Google and Full Text PDF PubMed Scopus Google Scholar, J. S. A. 1991; PubMed Scopus Google Scholar). Numerous studies using molecular that band proteins to a of proteins in They have been into the acid and AE3 the of the gene that Physiol. 1991; PubMed Scopus Google Scholar). More specifically, the AE1 gene the erythroid band 3 as as a truncated of the in J. Biol. Chem. Full Text PDF PubMed Google Scholar). AE1 were also recently found in J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). The are mainly expressed in and the AE3 are the in and Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). AE3 cDNA the was recently from a rat heart cDNA is to AE3 cDNA for and a of J. Biol. Chem. 1992; Full Text PDF PubMed Google blotting studies to the of the in whole is not the translation are in cardiomyocytes and proteins are anionic this was to band proteins expressed in cardiac cells and to proteins the anionic exchange function. of and Physiol. 1991; PubMed Scopus Google Scholar). AE1 and AE3, in the J. Biol. Chem. 1991; Full Text PDF PubMed Google a to be of the a antibody raised against the erythroid band 3 was to band proteins in cardiac tissue. proteins of apparent molecular masses of 80 and 120 were found in adult The two proteins were only in the membrane from adult rat isolated cardiac a of Confocal microscopy of immunostained adult rat showed the of the proteins at the sarcolemma and Using an antiserum specific to AE1 and an antibody specific to AE3, the 80- and 120-kDa proteins were characterized as of AE1 and AE3 Furthermore, that or both proteins perform the anionic exchange in cardiac