IMMUNOCHEMICAL QUANTIFICATION OF SARCOPLASMIC-RETICULUM CA2-ATPASE AND CALSEQUESTRIN IN MUSCLE BIOPSIES FROM PATIENTS WITH MYOTONIA-CONGENITA AND PARAMYOTONIA-CONGENITA EULENBURG()

A sensitive enzyme-linked immunoadsorbant assay was developed to quant ify Ca2+-ATPase and calsequestrin from sarcoplasmic reticulum in human muscle biopsies. Tissue levels of Ca2+-ATPase and calsequestrin avera ged 51.5 +/- 28.1 and 6.4 +/- 1.8mg/g muscle protein, respectively, in control muscles (means +/- SD, n = 12). The high sensitivity and spec ificity of the antibodies make the assay a useful tool in the diagnosi s of human neuromuscular disorders where defects in sarcoplasmic retic ulum function may be expected. The assay was applied to muscle biopsie s from patients with myotonia congenita and paramyotonia congenita Eul enburg. The calsequestrin concentration was normal in all patient musc les. The Ca-2+-ATPase content was also within the normal range but var ied considerably with the percentage distribution of slow-twitch fibre s. This indicates that the prolonged relaxation observed in the muscle s of patients with these disorders is not caused by faulty expression of Ca2+-ATPase and calsequestrin.