CONICET | Buscador de Institutos y Recursos Humanos

Functional antibodies against the cardiac electrogenic Na+/ HCO3- cotransporter: Potential therapeutic tool? Alejandro Orlowski, Verónica C. De Giusti, Gladys Chiappe de Cingolani, Bernardo V. Alvarez, Ernesto A. Aiello. Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, UNLP, La Plata, Argentina. The Na+/HCO3- cotransport (NBC) regulates cardiac intracelular pH (pHi). There are at least two isoforms of NBC in the cardiomyocyte, the electrogenic NBC1 and the electroneutral NBC3. We generated two functional antibodies against extracellular loop domains (Acd3 y Acd4) from heart NBC1. pHi was monitored using fluorescence measurements of BCECF in cat ventricular myocytes. The transport activity of total NBC and of NBC1 in isolation were evaluated during recovery from acidosis with an ammonium pulse (data expressed as H+ flux, JH, at pHi 6.8) and membrane depolarization with high extracellular potassium (K+ pulse, data expressed as DpHi), respectively. * indicates p<0.05 vs control. The antibodies recognized the NBC1 in western blot and immunostaining of myocytes. The K+ pulse produced a control pHi increase of 0.18±0.006 (n=5) which was abolished by the Acd3 (0.016±0.019*; n=5). This antibody decreased the JH by 50% (0.59±0.08* vs 1.32±0.19, n=5). Surprisingly, during the K+ pulse, the Acd4 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, p<0.05). We conclude that both antibodies are capable of recognizing the NBC1, but they have opposite effects on the function of this transporter: the Acd3 is inhibitory and the Acd4 is excitatory. The use of these antibodies could be important for selective studies on the pathophysiology of heart NBC1, opening a path for their potential use in therapeutic treatment.