Meeting Abstract

P1.92  Monday, Jan. 4  Net ³H-L-histidine transport across lobster intestine is stimulated by luminal zinc WOJNARWSKY, Pandora K. L.*; AHEARN, Gregory A.; University of North Florida, Jacksonville; University of North Florida, Jacksonville P.Lee@UNF.edu

The effects of luminal zinc on net transmural transport of ³H-L-histidine across perfused intestine of American lobsters (Homarus americanus) were measured. Unidirectional mucosal to serosal (MS) and serosal to mucosal (SM) fluxes were measured by adding 20 µM ZnCl₂ and variable concentrations of ³H-L-histidine (5 to 10000 µM) to either the perfusate or bath, respectively, and periodically sampling the appearance of radioactivity on the opposite side of the intestine. The direction and magnitude of net amino acid flux was calculated as the difference in the two unidirectional fluxes. ³H-L-histidine transport (MS flux) was a sigmoidal function of luminal [histidine] at the low substrate concentration range (5-100 µM) and was not affected by luminal zinc. ³H-L-histidine MS flux at the high substrate concentration range (1-10 mM) was also sigmoidal, but was significantly enhanced by the presence of luminal zinc. The dipeptide, glycylsarcosine, significantly inhibited MS ³H-L-histidine flux in the presence of zinc. SM amino acid transport kinetics at both low and high concentrations were linear functions of [histidine] and not stimulated by serosal zinc. Net fluxes of ³H-L-histidine toward the blood occurred at both low and high amino acid concentrations, but only the absorptive flux at amino acid concentrations from 1-10 mM was significantly stimulated by luminal zinc. Results suggest the presence of high and low affinity intestinal ³H-L-histidine transporters. The latter carrier system was zinc-dependent and apparently shared by the dipeptide, glycylsarcosine. Supported by NSF grant IBN04-21986.