Influence of chemical pollution on brain adenosine receptors of Mugil cephalus

The aim of this study was to investigate adenosine receptor sites in whole brain membranes of the saltwater teleost fish, Mugil cephalus, using the Al receptor selective agonist, [H-3]- N-6-cyclohexyladenosine ([H-3]-CHA). Sp ecific binding was saturable and reversible. A single class of high-affinit y binding sites was identify, showing K-d and B-max values of 1.43 +/- 0.26 nM and 69.5 +/- 5.4 fmol/mg protein, respectively. In competition experime nts, the following adenosine analogues, CHA, (2-[p-(2-carboxyethyl)-phenyle thylamino]-5'-N-ethylcarboxamidoadenosine) (CGS21680), 5'-(N-cyclopropyl)ca rboxamidoadenosina (CPCA) and N-6-[2-(3,5-dimethoxyphenyl)-2-(2methylphenyl )-ethyl]adenosine (DPMA), displaced [H-3]-CHA specifically bound to brain m embranes, revealing that the high-affinity binding sites have some pharmaco logical properties of mammalian Al adenosine receptors. Furthermore, our fi ndings indicate that in captivity chemical pollution determines a decrease of the K-d value corresponding to a 5-fold increase in affinity, whereas it does not induce any variation of the receptor density. (C) 1998 Elsevier S cience Ltd. All rights reserved.