Quantitative determination of growth hormone by immunoblotting

Blotting techniques have been extensively used, not only analytically for protein identification, but also preparatively to isolate and purify specific proteins from a large variety of cellular extracts and biological fluids. The process involves the separation of proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transfer of proteins to nitrocellulose membranes, and immunostaining to identify proteins which often are at very low concentrations. Because of the quantitative interactions of the proteins with specific antibodies, we have coupled the immunoblot procedure with photographic and densitometric methods for the quantitative determination of bovine growth hormone (bGH). In this way, the method is suitable for bGH detection and quantitation for a small number of samples by use of a single Western blot analysis. The sensitivity of this method permits determinations of bGH to 0.5 ng. The method uses a comparative procedure in which purified bovine growth hormone is used as a standard.