Rapid quantitation of uncoupling protein in brown adipose tissue mitochondria by a dot immunobinding ("dot blot") procedure: application to the measurement of uncoupling protein in Richardson's ground squirrel, rats, and mice

A dot immunobinding ("dot blot") method for measuring uncoupling protein in brown adipose tissue mitochondria is described. Mitochondrial proteins were solubilized in sodium dodecyl sulfate and applied directly to a nitrocellulose membrane housed in a 96-well microfiltration manifold. Spare binding sites on the nitrocellulose membrane were blocked with bovine serum albumin and then anti-(uncoupling protein) serum was applied. The antigen-antibody complex was detected by the addition of 125I-labelled protein A. Each nitrocellulose "dot" was cut out and its radioactivity was counted. A calibration curve was constructed from purified uncoupling protein standards, taken through the entire procedure. The dot immunobinding method is sensitive (nanogram quantities of uncoupling protein), and in contrast to conventional radioimmunoassay and enzyme-linked immunosorbent assay procedures, it is also rapid and appears to be very robust. The method has been successfully applied to the measurement of uncoupling protein in brown adipose tissue mitochondria of Richardson's ground squirrel, rats, and mice.