Radioimmunological Measurement of Beta-Endorphin in Equine Plasma

Abstract
Radioimmunoassay procedures were developed and validated for the quantification of .beta.-endorphin (.beta.-EP)-like immunoreactivity in equine plasma. .beta.-EP could be quantitatively extracted from plasma with silicic acid powder and subsequently assayed; however, valid estimates of this hormone could also be obtained on unextracted plasma. Although .beta.-lipotropin (.beta.-LPH) cross-reacted in the assay, it was not necessary to correct for .beta.-LPH activity when assaying unextracted plasma because chromatographic analyses showed that 92% of the immunoreactivity in plasma extracts was similar in MW to authentic .beta.-EP (1-31). In addition electroacupuncture treatment did not alter the relative proportion of immunoreactivity among different MW fractions.