Pancreatic ducts secrete a bicarbonate-rich secretion, the mechanism of which is not fully understood. The underlying mechanism is thought to involve several secondary active transporters residing in plasma cell membranes. The aim of the present study was to investigate whether rat pancreatic ducts possess the primary active transporter, namely a H⁺/K⁺-pump. Single small intralobular ducts were loaded with BCECF, stimulated with secretin and intracellular pH, pHi, was monitored in different conditions, especially as a recovery after ammonium pre-pulse. Large part of the pHi recovery was dependent on extracellular Na⁺ and HCO₃^-, and transporters responsible were NHE, NBC and AE. Under these conditions the H⁺/K⁺-pump inhibitors omeprazol and SCH28080 had very limited effects. However, when extracellular Na⁺ and HCO₃^-were removed, there was a significant residual pHi recovery, and this was eliminated by omeprazol, SCH28080 and K⁺-free solutions. These data show for the first time that rat pancreatic ducts possess functional H⁺/K⁺-pump that is able to regulate pHi and we propose that it is also involved in HCO₃^-secretion that is evoked by secretin stimulation.

Supported by the Danish Natural Science Council