Radioimmunoassays (RIAs) selective for methionine‐enkephalin (Met‐ENK) and leucineenkephalin (Leu‐ENK) have been developed using competition towards binding of 10 pM 125 I‐enkephalins to antibodies raised in rabbits against ENKs coupled to ovalbumin with carbodiimide. The high sensitivity of the RIAs (IC 50 0.57 n m and 0.55 n m for Met‐ and Leu‐ENK, respectively) allowed estimation of the enkephalin content in extracts of all rat brain regions. Regional levels are compared with those determined on the same extracts by a radioreceptor assay (RRA) using competition towards binding of 5 n m [ 3 H]Leu‐ENK to rat striatal membranes. Optimal conditions for killing the animals and extracting the endorphins have been carefully investigated: killing by rapid microwave irradiation was not found necessary as long as brain regions were homogenized into 0.1 n ‐HCl before deproteinization. Marked differences both in total endorphins (RRA) and ENKs (RIA) between regions are observed with similar ranking of the various regions: highest levels are found in striatum and hypothalamus and lowest in cerebellum and hippocampus. In each region the total ENK levels (RIA) represent only 2–13% of the total endorphins (RRA) suggesting the presence of large amounts of endorphins other than the ENKs.
No takes yet. Share an insight, caveat, or question.
Gros et al. (1978) studied this question.
Synapse has enriched 3 closely related papers on similar clinical questions. Consider them for comparative context: