CONICET | Buscador de Institutos y Recursos Humanos

Background and purpose: Na+/HCO3 - cotransport (NBC) regulates intracellular pH (pHi) in the heart. Herein, we focus our attention on the electrogenic NBC isoform NBCe1 by examining the effect of functional antibodies against it. Experimental approach: 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. pHi 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-induced acidosis (expressed as H+ flux, JH, in mM/min at pHi 6.8) and during membrane depolarization with high extracellular potassium (potassium pulse, expressed as DpHi), respectively. * indicates p<0.05 vs control. Key results: The potassium pulse produced a pHi increase of 0.18±0.006 (n=5), which was reduced by the a-L3 (0.016±0.019*; n=5). a-L-3 decreased the JH by 50% (0.59±0.08* vs. control, 1.32±0.19, n=5). Surprisingly, during the potassium pulse, a-L4 induced a higher pHi increase than control (0.25±0.018*, n=6), whereas the recovery of pHi from acidosis was accelerated (JH: 2.27±0.29*, n=6). 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 and implications: We conclude that both antibodies recognize NBCe1, but they have opposite effects on this transporter function: the a-L3 is inhibitory and the a-L4 is excitatory. The use of these antibodies could be important for selective studies on the pathophysiology of NBCe1 in heart, opening a path for their potential use in therapeutic treatment.