title: Antibodies against the cardiac sodium/bicarbonate co-transporter (NBCe1) as pharmacological tools.
abstract: OBJECTIVE
  Na(+) /HCO(3) (-) co-transport (NBC) regulates intracellular pH (pH(i) ) in the heart. We have studied the electrogenic NBC isoform NBCe1 by examining the effect of functional antibodies to this protein.
  
  
  METHODS
  We generated two antibodies against putative extracellular loop domains 3 (a-L3) and 4 (a-L4) of NBCe1 which recognized NBCe1 on immunoblots and immunostaining experiments. pH(i) was monitored using epi-fluorescence measurements in cat ventricular myocytes. Transport activity of total NBC and of NBCe1 in isolation were evaluated after an ammonium ion-induced acidosis (expressed as H(+) flux, J(H) , in mmol·L(-1)  min(-1) at pH(i) 6.8) and during membrane depolarization with high extracellular potassium (potassium pulse, expressed as ΔpH(i) ) respectively.
  
  
  RESULTS
  The potassium pulse produced a pH(i) increase of 0.18 ± 0.006 (n= 5), which was reduced by the a-L3 antibody (0.016 ± 0.019). The a-L-3 also decreased J(H) by 50%. Surprisingly, during the potassium pulse, a-L4 induced a higher pH(i) increase than control,(0.25 ± 0.018) whereas the recovery of pH(i) from acidosis was faster (J(H) was almost double the control value). In perforated-patch experiments, a-L3 prolonged and a-L4 shortened action potential duration, consistent with blockade and stimulation of NBCe1-carried anionic current respectively.
  
  
  CONCLUSIONS
  Both antibodies recognized NBCe1, but they had opposing effects on the function of this transporter, as the a-L3 was inhibitory and the a-L4 was excitatory. These antibodies could be valuable in studies on the pathophysiology of NBCe1 in cardiac tissue, opening a path for their potential clinical use.
authors: Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
authors: Verónica C
authors: VC
authors: De Giusti
authors: Alejandro
authors: A
authors: Orlowski
authors: María C
authors: MC
authors: Villa-Abrille
authors: Gladys E Chiappe
authors: GE
authors: de Cingolani
authors: Joseph R
authors: JR
authors: Casey
authors: Bernardo V
authors: BV
authors: Alvarez
authors: Ernesto A
authors: EA
authors: Aiello
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