COUGHLIN, DJ; CAPUTO, ND; BOHNERT, KL; WEAVER, FE; Widener University; Widener University; Widener University; Widener University: Troponin-T and Longitudinal Variation in the Contractile Properties of Trout Muscle

The red or aerobic muscle from the anterior of rainbow trout (Oncorhynchus mykiss) activates (generates force) more quickly than that from the posterior. An analysis of the expression of the muscle protein Troponin T (TnT) revealed a significant correlation between muscle activation and expression patterns of this protein in rainbow trout. TnT is a Ca2+ binding protein in muscle and, in part, regulates muscle activation. Rainbow trout express two forms of TnT in their aerobic or slow red muscle (S1 and S2), and the differential expression of these two forms correlates with variations in contractile properties. A significant shift in expression was detected from anterior to posterior with TnT S1 (29.5 kD) becoming more dominant in the posterior red muscle relative to TnT S2 (28.5 kD). To explore the relationship of TnT expression to muscle activation, a similar study was carried out with brook trout/charr (Salvelinus fontinalis). For a total of eight fish, contractile properties were measured in anterior and posterior red muscle. Unlike rainbow trout, brook trout show no significant pattern in muscle activation: some fish display faster rates in the anterior, some in the posterior, and some show no variation. This leads to the prediction that, unlike rainbow trout, no consistent longitudinal patterns should be observed in TnT expression in brook trout. TnT analysis using the same methods as rainbow trout (hydroxy-apatite chromatography of myofibrillar proteins followed by SDS-PAGE) resulted in the identification of two red muscle isoforms of TnT: S1 (31.1 kD) and S2 (28.8 kD). For the eight fish used in the physiology experiments, TnT expression patterns in the red muscle will be analyzed, allowing correlation between activation time and protein expression in individual fish.