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JOINT RESEARCH PROJECT ON THE AQUATIC ECOTOXICITY OF ORGANO- ALUMINIUM :EFFECTS ON THE CALCIUM PHYSIOLOGY IN FISH

Objective

THIS REASEARCH FORMS PART OF A COOPERATIVE PROJECT WITH THE FOLLOWING INSTITUTES:
- SCK-CEN, MOL, BELGIUM
- NERC, THE FRESHWATER ASSOCIATION, WINDERMERE, UK.

THE OVERALL GOAL OF THE JOINT RESEARCH PROJECT IS TO RELATE THE TOXIC EFFECTS OF ALUMINIUM AND ITS ORGANO-COMPLEXES ON THE PHYSIOLOGY OF AQUATIC ORGANISMS TO THE UNDERLYING CHEMICAL AND PHYSIOLOGICAL PROCESSES INVOLVED, IN ORDER TO PREDICT THE IMPACT OF CHANGES IN THE ACIDIC FRESWATER ENVIRONMENT ON THE BIOTA.

THE EXPERIMENTAL CONDITIONS USED (WATER PH, WATER CALCIUM AND AL CONCEMTRATIONS) WILL BE SIMILAR TO THOSE THAT OCCUR IN SOME NATURAL WATER BODIES. FOR THIS PURPOSE NUMEROUS DATA ARE AVAILABLE THAT HAVE BEEN COLLECTED IN AN EXTENSIVE SURVEY IN THE NETHERLANDS, CARRIED OUT BY THE DEPARTMENT OF AQUATIC ECOLOGY OF THE UNIVERSITY OF NIJMEGEN.

1.- FIRST, THE EFFECTS OF AL3+ AND AL HYDROLYSIS PRODUCTS WILL BE STUDIED ON THE UPTAKE OF CA2+ FROM THE WATER. USING THE SO-CALLED ISOLATED HEAD TECHNIQUE - PROVIDING INSITU PREPARATION OF BRANCHIAL EPITHELIUM AND ALLOWING EXPERIMENTAL MANIPULATION OF EXTERNAL (WATER) AND INETRNAL (BLOOD-PLASMA) MEDIA - THE EFFECTS OF AL ON TRANSEPITHELIAL 45 CA FLUX AND ON GILL 45CA ACCUMULATION WILL BE EVALUATED. THE RESULTS OF THESE EXPERIMENTS WILL ALLOW CONCLUSIONS AS TO WHERE AL EXERTS ITS TOXIC EFFECTS (IE ON APICAL MEMBRANE CA2+ CHANNELS,ON CYTOSOLIC CA BINDING PROTEINS AND CYTOSOLIC CA2+ STORES OR ON THE BASOLATERAL MEMBRANE CA2+ PUMP.

THE PROPOSERS RECENTLY HAVE ELUCIDATED THE BIOCHEMICAL NATURE OF THE BRANCHIAL CALCIUM UPTAKE MEHANISMS IN SEVERAL FISH SPECIES. THE MECHANISMS ARE LOCATED IN SPECIALIZED CELLS (IONOCYTES). CALCIUM IONS ENTER THE CELLS PASSIVELY, VIA NON-VOLTAGEGATED CA2+-CHANNELS IN THE APICAL MEMBRANES. THEY ARE TRANSPORTED VIA CYTOPLASMIC CALCIUM-BINDING PROTEINS AND RELEASED INTO THE BLOOD VIA CA-PUMPS (CALMODULIN-DEPENDENT HIGH-AFFINITY CA2+-ATPASES) LOCATED IN THE BASOLATERAL CELL MEMBRANES OF THE IONOCYTES. THE INTERACTION OF AL WITH CALMODULIN AND OF CALMODULIN-AL COMPLEXES WITH THE TECHNIQUES THE PROPOSERS HAVE USED FOR THEIR STUDIES ON THE INTERACTIONS OF CD2+ WITH CALMODULIN-DEPENDENT PHOSPHODIESTERASE AND CA2+ TRANSPORT ATPASES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

STICHTING KATHOLIEKE UNIVERSITEIT
Address

6500 GL Nijmegen
Netherlands