Cellular mechanism underlying LPS-induced inhibition of in vitro L-leucine transport across rabbit jejunum.
Lipopolysaccharide (LPS) is a known causative agent of sepsis. In previous studies, we have shown that it reduces L-leucine mediated transport across the rabbit jejunum by about 30%. In this study, the mechanism(s) of LPS inhibition on amino acid transport were analysed in detail. LPS did not inhibit L-leucine transport across brush border membrane vesicles, suggesting the need for an intracellular step. The inhibitory effect of LPS was not altered by the addition of protein kinase A (PKA) inhibitor (IP(20), 10(-7) M) or an analog of cAMP (DB-cAMP, 3 x 10(-4) M), indicating that the PKA signal transduction pathway was not involved in the LPS effect. However, the inhibitory effect of LPS was suppressed by trifluoroperazine (10(-7) M), a Ca(2+)/calmodulin inhibitor and staurosporine (10(-7) M), an protein kinase C (PKC) inhibitor. Likewise, LPS inhibition disappeared in media without calcium. These results suggest that LPS could inhibit the intestinal uptake of L-leucine across the small intestine in vitro by intracellular processes related to calcium, involving PKC and calmodulin protein.
Abad
B
B
Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain.
Mesonero
J E
JE
Salvador
M T
MT
García-Herrera
J
J
Rodríguez-Yoldi
M J
MJ
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001427:Bacterial Toxins / Q000633:toxicity; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004768:Enterotoxins / Q000633:toxicity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D029968:Escherichia coli Proteins; D007408:Intestinal Absorption / Q000187:drug effects; D007583:Jejunum / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014867:Water / Q000378:metabolism
D000596:Amino Acids; D001427:Bacterial Toxins; D004768:Enterotoxins; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; D014867:Water; C027538:heat-labile enterotoxin, E coli; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D007930:Leucine; D002118:Calcium