EXPRESSION OF NA-ATPASE BETA-SUBUNIT ISOFORMS IN THE EUROPEAN EEL (ANGUILLA-ANGUILLA)(,K+)

Reverse transcriptase - polymerase chain reaction experiments utilisin g degenerate primers were used to demonstrate that the Na+,K+-ATPase b eta 3 but not beta 2 isoform was present in brain tissue from the Euro pean eel (Anguilla anguilla). Two cDNA fragments were cloned and seque nced yielding 445 nucleotides of the Na+,K+-ATPase beta 3 isoform sequ ence. The putative amino acid sequence translated from this nucleotide sequence shared 58.0, 50.6 and 50.3% homology with previously publish ed Na+,K+-ATPase ''beta 3-like'' isoform sequences from the clawed toa d (Xenopus laevis), the chicken (Gallus domesticus) and the toad (Bufo marinus) respectively. The size of the Na+,K+-ATPase beta 3 mRNA tran script in eel tissues was demonstrated to be 2.4 Kb. Detectable levels of Na+,K+-ATPase beta 3 mRNA were only found in brain tissue. The tis sue specific distribution of the beta 3 mRNA suggests that it plays li ttle or no direct role in the process of osmoregulation in tissues suc h as the intestine or gill.