MADHOUN, N.M.; WILWERT, J.L.; COUGHLIN, D.J.; Widener Univ., Chester, PA: Parvalbumin Correlates with Relaxation Rate in the Swimming Muscle of Sheepshead and Kingfish

Parvalbumin is a muscle protein that aids in relaxation from contraction. Parvalbumin binds myoplasmic Ca2+ during contractions, reducing calcium concentration and enhancing relaxation. Different isoforms of parvalbumin have varying affinities for calcium, and relaxation rates in skeletal muscle are affected by variations in the isoforms of parvalbumin expressed. This study examines the effect of parvalbumin isoforms on relaxation rate in the Sheepshead, Archosargus probatocephalus (Pisces, F. Sparidae). Sheepshead show longitudinal variation in relaxation rate, with anterior muscle displaying faster rates of relaxation than posterior. The hypothesis is that patterns of parvalbumin expression determine the relaxation rate along the length of Sheepshead for each of three skeletal muscle fiber types: white, pink and red. The prediction is that the types and relative expression of parvalbumin found in anterior red muscle will differ from the posterior. We suggest that anterior muscle will contain a greater amount of a parvalbumin isoform that has higher calcium affinity, contributing to a faster relaxation rate. We successfully employed protein electrophoresis (SDS-PAGE) with Western Blots to identify two parvalbumin isoforms in each muscle fiber type. SDS-PAGE and densitometry were used to determine the relative expression levels of the two parvalbumin isoforms. So far, in close agreement with our predictions, we have shown a correlation between the relaxation rate and parvalbumin expression in red muscle. Similar results have been observed in Southern Kingfish, Menticirrhus americanus (Pisces, F. Scianidae).