Hepatic activities of thiamine-dependent enzymes, glucose-6-phosphate dehydrogenase and cytochrome P4501A in Baltic salmon ( Salmo salar) yolk-sac fry after thiamine treatment

Abstract

Sea-run Baltic salmon ( Salmo salar) populations have been affected by the M74 syndrome since 1974 causing high yolk-sac fry losses in Swedish compensatory rearing plants. M74 has been shown to be a maternally transmitted thiamine (vitamin B 1) deficiency. The aim of this study was to investigate possible relationships between thiamine and hepatic activities of the thiamine-dependent enzymes transketolase (TK) and α-ketoglutarate dehydrogenase (α-KGDH) in addition to glucose-6-phosphate dehydrogenase (G6PDH) and cytochrome P4501A (CYP1A), measured as 7-ethoxyresorufin O-deethylase (EROD), in Baltic salmon yolk-sac fry after treatment with thiamine. Thiamine concentrations and activities of TK, α-KGDH and EROD were significantly lower ( P<0.05) in M74 groups compared to controls (not developing M74) and family groups of thiamine injected females. In M74-developing groups the thiamine immersions reduced the mortality from 86 to 13% and restored thiamine concentrations and activities of TK, α-KGDH and EROD to levels slightly lower than the immersed controls. An interesting fact was that the controls showed significantly elevated ( P<0.05) TK and α-KGDH-activities after immersions in thiamine, indicating that they also may have a stressed thiamine metabolism. The TK and α-KGDH-activities of unimmersed groups correlated significantly ( P<0.05) with the thiamine content. We suggest that the low activities of TK and α-KGDH in M74 groups may be an integrative part in the pathogenesis of M74 development.