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Cellular mechanism underlying LPS-induced inhibition of in vitro L-leucine transport across rabbit jejunum

Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain

J.E. Mesonero

Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain

M.T. Salvador

Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain

J. Garcia-Herrera

Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain

M.J. Rodriguez-Yoldi

Physiology Unit, Department of Pharmacology and Physiology, Veterinary Faculty, University of Zaragoza, Zaragoza, Spain, mjrodyol{at}posta.unizar.es

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 (IP₂₀, 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 Ca²⁺/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.

Journal of Endotoxin Research, Vol. 8, No. 2, 127-133 (2002)
DOI: 10.1177/09680519020080020601


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