Premium
Net transmural transport of 65Zn2+ across perfused intestine suggests an absorptive function for metals in the American lobster, Homarus americanus.
Author(s) -
Conrad Erik M,
Ahearn Gregory A
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a839-b
Subject(s) - homarus , ouabain , ion transporter , chemistry , flux (metallurgy) , vanadate , small intestine , metal , lumen (anatomy) , biophysics , medicine , biochemistry , biology , sodium , crustacean , membrane , ecology , organic chemistry
Lobster intestine was immersed in, and perfused with, a physiological saline with a salt composition and pH matching the hemolymph. Radiolabelled 65 Zn 2+ was either added to the perfusate (M to S flux measurements) or the bath (S to M flux measurements). Previous studies with this preparation indicated a significant carrier‐mediated M to S flux of 65 Zn 2+ and this flux was stimulated by luminal L‐histidine. In this study, S to M fluxes of 65 Zn 2+ (5 to 100 μM) also followed Michaelis‐Menten kinetics (K m = 28.03±8.81 μM; J max = 0.29±0.035 pmoles/cm 2 min −1 ), indicating carrier‐mediated metal transport from blood to lumen. Transmural transport (S to M) of 65 Zn 2+ significantly decreased (p<0.01) with the addition of the serosal inhibitors ouabain (16%), K + (42%), Ca 2+ (30%) Cu 2+ (38%), nifedipine (39%), and vanadate (53%), indicating inhibition of metal binding to the serosal aspect of the intestine. However, transmural transport was stimulated with the serosal addition of ATP (20%) and Na + (28%). These results suggest that S to M 65 Zn 2+ flux occurred by the combination of a carrier‐mediated process and an ion channel. Transmural M to S 65 Zn 2+ fluxes (5 to 100μM) were 3‐fold greater than S to M transport, and addition of luminal L‐histidine further enhanced net metal transfer to the blood. Overall, these data imply that metal transport by lobster intestine is absorptive and enhanced by luminal amino acids. Supported by NSF grant IBN04‐21986.