Calmodulin-mediated regulation of bicarbonate and lactate transports in rat jejunum.
OBJECTIVE
Ca(2+)/CaM is known to modulate the activity of several transport systems and its regulation can be accomplished either directly or via the involvement of specific protein kinases. Aim of this study was to investigate the possible role of Ca(2+)/CaM on bicarbonate and lactate transports in rat jejunal enterocyte.


METHODS
Enzymatic assays in isolated plasma membranes were performed. Moreover membrane vesicles, transiently opened and resealed, were loaded with Ca(2+) and calmodulin, both in the absence and in the presence of ATP, and were used after that to perform uptake studies.


RESULTS
Enzymatic assays gave evidence for the presence of Ca(2+)/CaM-dependent protein kinase II (CaMKII) in plasma membranes from rat jejunum. However, uptake experiments suggest that Ca(2+)/CaM, and not CaMKII, inhibits both basolateral Cl(-)/HCO(3)(-) exchange and H(+)-lactate symport, whilst HCO(3)(-) and Cl(-) conductances are unaffected. Neither Ca(2+)/CaM nor CaMKII seem to regulate brush border Na(+)/H(+) exchanger activity.


CONCLUSIONS
These data are consistent with a Ca(2+)/CaM-mediated reduction of bicarbonate and lactate exit from jejunal enterocyte.
Tosco
Marisa
M
Dipartimento di Fisiologia e Biochimica Generali, Universita di Milano, Via Celoria 26, 20133 Milan, Italy. marisa.tosco@unimi.it
Orsenigo
Maria Novella
MN
Gastaldi
Giulia
G
Faelli
Alide
A
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism; D002712:Chlorides / Q000737:chemistry / Q000378:metabolism; D020895:Enterocytes / Q000737:chemistry; D066298:In Vitro Techniques; D007583:Jejunum / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000737:chemistry; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D001639:Bicarbonates; D002147:Calmodulin; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium