Radioelectrophoresis: a specific microassay for parvalbumins. Application to muscle biopsies from man and other vertebrates.

A two-dimensional radioelectrophoretic method is described, by which parvalbumins from minute biopsy samples (approx. 50 mg) can be detected and quantitated by their 45Ca2+-binding properties. In the first dimension, parvalbumins are purified by sieving through a gradient polyacrylamide gel and collected at the bottom of the electrophoresis tubes. The second dimension is a disc electrophoresis in the presence of 45Ca2+. Parvalbumins can thus be identified and quantitated by three criteria: low molecular weight, acidic character and calcium-binding properties, since they are never exposed to denaturing conditions. Validity of the technique was demonstrated on carp myogen, and on extracts from rabbit psoas and heart muscles. Application of this method to the shrew fast beating myocardium shows that it does contain parvalbumin, in agreement with the proposed role of soluble relaxing factor (Pechère et al. (1977) FEBS Lett. 75, 111--1141. When applied to human muscle biopsies, radioelectrophoresis points to an uneven distribution of parvalbumin among different skeletal muscles. For the human limb muscles tested in this study, the parvalbumin content is similar to that of rabbit psoas muscle.