Expression of the electrogenic Na+-HCO3--cotransporter NBCe1 in tumoral insulin-producing BRIN-BD11 cells.
OBJECTIVE
The expression of the electrogenic Na+-HCO3--cotransporter NBCe1 was recently documented in rat pancreatic islet B-cells, it being speculated that such a protein participates in the extrusion of bicarbonate generated by the oxidative catabolism of nutrients from insulin-producing cells. Considering the prevalence of a Crabtree effect in tumoral insulin-producing cells, the possible presence of NBCe1 was now investigated in BRIN-BD11 cells, an insulin-producing cell line established by electrofusion of normal pancreatic B-cells with immortalized RINm5F cells.


METHODS
The possible presence of NBCe1 in BRIN-BD11 cells was investigated by RT-PCR, western blot analysis and immunocytochemistry. The release of insulin and net uptake of 22Na+ were also measured in the BRIN-BD11 cells.


RESULTS
RT-PCR, western blot analysis and immunocytochemistry documented the presence of NBCe1 in BRIN-BD11 cells. A reported inhibitor of NBCe1, i.e. tenidap, (50-100 microM), inhibited basal and hypotonicity-induced insulin release from the BRIN-BD11 cells, whilst increasing the net uptake of 22Na+ by the same cells. The latter effect was, in relative terms, more pronounced in the presence than absence of ouabain.


CONCLUSIONS
BRIN-BD11 cells, like normal pancreatic islet B-cells, express NBCe1, with predominance of the B variant of this electrogenic Na+-HCO3--cotransporter.
Bulur
Nurdan
N
Laboratory of Experimental Hormonology, Université Libre de Bruxelles, Brussels.
Virreira
Myrna
M
Soyfoo
Muhammed S
MS
Louchami
Karim
K
Delporte
Christine
C
Perret
Jason
J
Beauwens
Renaud
R
Malaisse
Willy J
WJ
Sener
Abdullah
A
D000818:Animals; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005452:Fluoresceins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000378:metabolism; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D007150:Immunohistochemistry; D007211:Indoles / Q000378:metabolism / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D000078183:Oxindoles; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors
D005452:Fluoresceins; D005456:Fluorescent Dyes; D007211:Indoles; D007328:Insulin; D000078183:Oxindoles; D020033:Protein Isoforms; C422004:Slc4a4 protein, rat; D027982:Sodium-Bicarbonate Symporters; C007293:DAPI; D010042:Ouabain; C062866:tenidap; D012964:Sodium; D005947:Glucose