L-proline transport by purified cell types of lobster hepatopancreas

Characterization of cadmium transport in hepatopancreatic cells of a mangrove crab Ucides cordatus: The role of calcium

Cadmium is a toxic metal, present in batteries and discarded in estuaries and mangrove habitats. Apart from that, it is a non-essential metal that causes toxic effects in many organisms. Cadmium accumulates in gills and hepatopancreas of crustaceans and its route into the cell is unknown. It is possible that occurs by calcium channels or calcium transporters. The objective of this study was to characterize the transport of cadmium and the role of calcium in different cell types from hepatopancreas of the mangrove crab Ucides cordatus. For this, the hepatopancreas was dissociated by magnetic stirring and after that separated by a sucrose gradient. Then, the cells were labeled with FluoZin-3 AM and different CdCl₂ concentrations were added together with a variety of inhibitors. The results showed that Cd²⁺ transport occurs differently in each cell type from hepatopancreas and is partially explained by the function the cells perform in this organ. Embryonic (E) and Resorptive (R) cells transported more Cd²⁺ compared to Fibrillar (F) and Blister (B) cells. R cells responded to Ca²⁺ channel inhibitors and intracellular Ca²⁺ manipulations positively, as the other cell types and in a stronger way. B cells were the least responsive to Ca²⁺ channel inhibitors and, unlike the other cells, showed a competition of Cd²⁺ with intracellular Ca²⁺ manipulations. The results indicate that Ca²⁺ affects the transport of Cd²⁺ in hepatopancreatic cells of Ucides cordatus and uses Ca²⁺ channels to enter these cells. In addition, information about Ca concentration could be used as a mitigating factor for Cd accumulation in crabs' hepatopancreas.

Cytochemical characterization of gill and hepatopancreatic cells of the crab Ucides cordatus (Crustacea, Brachyura) validated by cell metal transport

Ucides cordatus (Linnaeus, 1763) is a hypo-hyper-regulating mangrove crab possessing gills for respiratory and osmoregulatory processes, separated in anterior and posterior sections. They also have hepatopancreas, which is responsible for digestion and absorption of nutrients and detoxification of toxic metals. Each of these organs has specific cells that are important for in vitro studies in cell biology, ion and toxic metals transport. In order to study and characterize cells from gills and hepatopancreas, both were separated using a Sucrose Gradient (SG) from 10 to 40% and cells in each gradient were characterized using the vital mitochondrial dye DASPEI (2-(4-dimethylaminostyryl)-N- ethylpyridinium iodide) and Trichrome Mallory's stain. Both in 20 and 40% SG for gill cells and 30% SG for hepatopancreatic cells, a greater number of cells were colored with DASPEI, indicating a larger number of mitochondria in these cells. It is concluded that the gill cells present in 20% and 40% SG are Thin cells, responsible for respiratory processes and Ionocytes responsible for ion transport, respectively. For hepatopancreatic cells, the 30% SG is composed of Fibrillar cells that possess larger number of membrane ion and nutrient transporters. Moreover, the transport of toxic metal cadmium (Cd) by isolated hepatopancreatic cells was performed as a way of following cell physiological integrity after cell separation and to study differences in transport among the cells. All hepatopancreatic cells were able to transport Cd. These findings are the first step for further work on isolated cells of these important exchange epithelia of crabs, using a simple separation method and to further develop successful in vitro cell culture in crabs.

Identification of a novel sodium-dependent fructose transport activity in the hepatopancreas of the Atlantic lobster Homarus americanus

[(3)H]Fructose and [(3)H]glucose transport were determined in brush-border membrane vesicles (BBMV), basolateral membrane vesicles (BLMV) and isolated cells (E, R, F, B) of H. americanus (Atlantic lobster) hepatopancreas. Glucose transport in BBMV was equilibrative in the absence of sodium and concentrative in the presence of sodium. Sodium-dependent glucose transport by BBMV was not inhibited by a tenfold molar excess of fructose. Glucose transport by BLMV was equilibrative and sodium independent. Fructose uptake by BBMV and BLMV was equilibrative in the absence of sodium and concentrative in the presence of sodium. This enhancement was not affected by a tenfold molar excess of glucose in the presence of sodium. E-, F- and B-cells showed sodium-dependent uptake of fructose, while R-cells did not. Sodium-dependent fructose uptake by E-cells was not inhibited by a tenfold molar excess of glucose or mannose. Western blot analysis of BBMV, BLMV and E-, R-, F- and B-cells using rabbit polyclonal antibodies directed against epitopes of mammalian GLUT2, GLUT5, SGLT1 and SGLT4 indicated the presence of cross-reacting lobster proteins. Sequence alignment of the mammalian proteins with translated, lobster expressed sequence tags also indicated significant identity between species. Comparison of fructose and glucose uptake in the absence and presence of sodium by BBMV, BLMV and isolated cells indicated the presence of a distinct sodium-dependent transport activity for each sugar in the Atlantic lobster.