Adaptation Of Isolated Spiny Dogfish Shark Choroid Plexus To Manipulation Of Extracellular Zn And Exposure To Cd

The choroid plexus forms the blood‐cerebrospinal fluid (CSF) barrier, secretes CSF and transports solutes between blood and CSF. We reported for spiny dogfish shark (S. acanthias) that choroid plexus accumulated essential metals, e.g., zinc (Zn), and contaminant heavy metals to concentrations similar to those in kidney and liver. Using isolated dogfish choroid plexus, our objective is to characterize regulation of gene expression and modulation of epithelial ultrastructure by the essential mineral Zn and the contaminant metal, cadmium (Cd). To begin, effects of Zn supplementation or depletion and exposure to Cd on metallothionein (MT) gene expression were analyzed by qRT‐PCR; epithelial ultrastructure was viewed by transmission electron microscopy (TEM). Initial TEM images of Zn‐supplemented and Zn‐depleted choroid plexus show modest changes in apical microvilli and no remarkable variations in basolateral in‐foldings as compared to control tissues. Nevertheless, 10 μM Zn supplementation increased MT mRNA by 275‐fold at 24 h and by 620‐fold at 48h, whereas 24‐h chelation of extracellular Zn with 10 μM diethylentriamene pentaacetate reduced MT mRNA by 60%. 500 nM Cd increased MT mRNA by 65‐fold at 24 h. These initial data suggest that in dogfish choroid plexus although epithelial ultrastructure might remain unchanged, altered Zn availability and Cd exposure regulate MT gene expression. NSF‐IOS#1052654