Crustaceans found in metal-contaminated regions are able to survive, and the authors investigated the physiological mechanisms involved by comparing populations from contaminated and noncontaminated areas. The objective of the present study was to measure the cellular transport of a nonessential metal (cadmium [Cd]) in gills and hepatopancreas of Ucides cordatus, together with cell membrane fluidity, metallothionein levels, and lipid peroxidation. The 2 populations compared were from a polluted and a nonpolluted mangrove area of São Paulo State, Brazil. The authors found, for the first time, larger Cd transport in gills and hepatopancreatic cells from crabs living in polluted mangrove areas. The cells also had lower plasma membrane fluidity, increased lipid peroxidation and less metallothionein compared to those from nonpolluted regions. The authors also found larger amounts of Cd in intracellular organelles of gills, but not in the hepatopancreas, from crabs in polluted regions. Therefore, in polluted areas, these animals showed higher Cd transport and lower plasma membrane fluidity and storage of Cd intracellularly in gill cells, whereas hepatopancreatic cells used metallothionein as their main line of defense. The findings suggest that crabs from polluted areas can accumulate Cd more easily than crabs from nonpolluted areas, probably because of an impairment of the regulatory mechanisms of cell membrane transport. Environ Toxicol Chem 2017;36:361-371. © 2016 SETAC.

The gills contain essential cells for respiration and osmoregulation, whereas the hepatopancreas is the site of digestion, absorption, and nutrients storage. The aim of this work was to separate and characterize gill and hepatopancreatic cells of the mangrove crab, Ucides cordatus. For gills, the methodology consisted of an enzymatic cellular dissociation using Trypsin at 0.5%, observation of cellular viability with Tripan Blue, and separation of cells using discontinuous sucrose gradient at concentrations of 10%, 20%, 30%, and 40%. The hepatopancreatic cells were dissociated by magnetic stirring, with posterior separation by sucrose gradient at the same concentrations above. For gills, a high cellular viability was observed (92.5±2.1%), with hemocyte cells in 10% sucrose layer (57.99 ± 0.17%, *P < 0.05), principal cells in the 20% sucrose layer (57.33 ± 0.18, *P < 0.05), and thick cells and pillar cells in the 30% and 40% sucrose layers, respectively (39.54 ± 0.05%, *P < 0.05; and 41.81 ± 0.04%, *P < 0.05). The hepatopancreatic cells also showed good viability (79.22 ± 0.02%), with the observation of embryonic (E) cells in the 10% sucrose layer (67.87 ± 0.06%, **P < 0.001), resorptive (R) and fibrillar (F) cells in the 20% and 30% sucrose layers (44.71 ± 0.06%, **P < 0.001, and 43.25 ± 0.01%, *P < 0.05; respectively), and blister (B) cells in the 40% sucrose layer (63.09 ± 0.03%, **P < 0.001). The results are a starting point for in vitro studies of heavy metal transport in isolated cells of the mangrove crab U. cordatus, subjected to contamination by metals in the mangrove habitat where they are found.

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The crustacean intestine and hepatopancreas display a variety of solute transport mechanisms for transmembrane transfer of dietary contents from lumen to epithelial cytosol. An in vitro intestinal perfusion apparatus was used to characterize mucosal to serosoal (MS) and serosal to mucosal (SM) Zn(2+) -dependent (3)H-L-leucine transport by the intestine of the American lobster, Homarus americanus. Transmural 20 µM MS (3)H-L-leucine fluxes across lobster intestine were a hyperbolic function of luminal zinc concentration (1-50 µM) following Michaelis-Menten kinetics (K(m) = 2.67 ± 0.74 µM; J(max) = 19.56 ± 2.22 pmol/cm(2) ×min). Transmural 20 µM SM (3)H-L-leucine fluxes were not affected by serosal zinc, resulting in a highly significant stimulation of net amino acid transfer to the blood by luminal metal. MS fluxes of 20 µM (3)H-L-leucine were also hyperbolic functions of luminal [Cu(2+)], [Mn(2+)], [Na(+)], and [H(+)]. MS flux of (3)H-L-leucine was a sigmoidal function of luminal [L-leucine] and was stimulated by the addition of 20 µM luminal zinc at both pH 7.0 and 5.5. A greater enhanced amino acid transport occurred at the lower pH 5.5. MS flux of 20 µM (3)H-L-leucine in the presence of 20 µM zinc was significantly inhibited by addition of 100 µM luminal glycylsarcosine, and MS flux of 20 µM (3)H-glycylsarcosine was inhibited by 100 µM L-leucine in the presence of 20 µM zinc. Results suggest that (3)H-L-leucine and metals form a complex (e.g., Leu-Zn-Leu] that may functionally mimic dipeptides and use a dipeptide-like transporter during MS fluxes as suggested for fish and mammals.

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