Detection from rat pituitary of beta-lipotropin and materials containing opiatelike activity by combined enzymatic radioreceptor assay.
Tonin, a proteolytic enzyme isolated from rat submaxillary gland, was allowed to react upon ovine beta-lipotropin (beta-LPH) at 37 degrees C at a variety of pH values and for different lengths of time. Opiatelike activity generated by the reaction was assessed using a radioreceptor assay for beta-endorphin with rat brain homogenate. [3H]naloxone, and beta-endorphin as receptors, tracer, and hormone standard, respectively. Cleavage of beta-LPH with tonin produced a 10-fold increase in opiatelike activity as compared with beta-LPH alone. Digestion of beta-LPH with other enzymes such as renin, cathepsin D, trypsin, and chymotrypsin produced much less opiatelike activity. beta-Endorphin and methionine-enkephalin were not cleaved by tonin. Using this new assay, we were able to detect beta-LPH and materials containing opiatelike activity from rat pituitary extracts after gel chromatography. It is more specific and more sensitive than trypsin digest.
D000818:Animals; D004723:Endorphins / Q000032:analysis*; D004744:Enkephalin, Methionine; D004745:Enkephalins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D010902:Pituitary Gland / Q000032:analysis*; D011869:Radioligand Assay / Q000379:methods; D051381:Rats; D013997:Time Factors; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000032:analysis*
D004723:Endorphins; D004745:Enkephalins; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D008083:beta-Lipotropin