Parvalbumin isotypes in white muscle from three teleost fish: Characterization and their expression during development

Parvalbumin isotypes were isolated by chromatography from trunk white muscle of rainbow trout (Oncorhynchus mykiss W.), brown trout (Salmo trutta L.), and sea bass (Dicentrarchus labrax L.). Five, four and two components were respectively purified and physico-chemically characterized. Expression of the various isotypes was followed in the course of the fish development and, in adult fish, from the anterior to the posterior myotomes. Isotype distribution varies both chronologically and spatially. In trout, parvalbumins occur around hatching; as the fish develop, transitions occur in isotype expression, PA II appearing as the predominant larval form and PA III, IV, or V as the main adult form, as previously observed in Barbus barbus (L.). In the sea bass, the developmental expression pattern is more unexpected: the synthesis of both isotypes (PA II and PA V) is delayed and the larval form PA II remains the principal isotype in adult fish. These observations indicate that the polymorphism of parvalbumins in fish constitutes a subtle mechanism modulating the speed and power of muscle contraction. Our results support the view that each isotype plays a specific role in relation to the muscle activity required in fish at a given developmental stage or a given trunk level in the adult.