Isolation and characterization of parvalbumins from skeletal muscles of a tropical amphibian, Leptodactylus insularis.

Parvalbumins were isolated from skeletal muscles of a tropical amphibian, Leptodactylus insularis, and three new isotypes were identified. The total concentration of parvalbumins in L. insularis was the same as the total amounts found in an amphibian from the temperate or variable zone (Rana temporaria). Muscles of the thigh and foreleg had the maximum parvalbumin concentration (0.35 mmol.kg wet weight-1). Samples from pectoralis and rectus abdominis muscles had significantly less (0.29 mmol.kg-1). Three previously unknown parvalbumin isotypes (IV, IIIa, and IIIb) were isolated from the tropical amphibian. They were different from the isotypes (IVa and IVb) predominant in R. temporaria skeletal muscle. Parvalbumins are thought to have a role in the short-term removal of myoplasmic Ca2+ during muscle relaxation. Hence, the unique isotypes in L. insularis may reflect optimal molecular adaptations retained during the animal's evolution in a constantly warm environment.