PKA regulation of bicarbonate and lactate movements across rat jejunal plasma membranes.

Background/Aims: Evidence was previously given that the mechanisms involved in bicarbonate and lactate movements across rat jejunal enterocyte are modulated by PKC and Ca2+/CaM. Aim of this study was to investigate the possible role of PKA on bicarbonate and lactate transports. Methods: Enzymatic assays in isolated plasma membranes were performed. Moreover membrane vesicles, transiently opened and resealed, were treated with a phosphorylating solution (leading to PKA activation) and were used after that to perform uptake studies. Results: Enzymatic assays give evidence for the presence of PKA in plasma membranes from rat jejunum. Uptake experiments suggest that PKA stimulates the two systems that accomplish basolateral HCO3- efflux from the enterocyte, namely Cl-/HCO3- exch anger and HCO3- conductance, without affecting HCO3- influx from the lumen mediated by Na+/ H+ exchanger activity. Moreover basolateral H+-lactate symporter is stimulated by PKA, as well as the brush border isoform of Na+-glucose cotransporter SGLT1. Conclusion: PKA activation evokes individual responses that could be coordinated through cellular metabolism. Copyright (C) 2004 S. Karger AG, Basel.