Beta-endorphin does not protect alkylation of opiate receptor by N-ethylmaleimide.
Rat brain membranes were incubated in N-ethylmaleimide (NEM, 0.5-1.0 mM) in the presence and absence of various concentrations of morphine, Leuenkephalin and human beta-endorphin (beta h-EP). After sufficient washing, the binding of dihydromorphine (DHM), [D-Ala-D-Leu]-enkephalin (DADLE) and tritiated beta h-EP was 10-40% above that of membranes treated with NEM alone. There was no additive effect of morphine and Leu-enkephalin with respect to their effect on recovery of beta h-EP binding. Evaluation of beta h-EP as protecting ligand proved to be difficult since preincubation completely inhibits subsequent DHM and DADLE binding unless a more extensive washing protocol is employed. A protocol for washing beta h-EP preincubated membranes using a Tris-phosphate buffer of pH 6 containing 150 mM NaCl, 20 mM MgCl2 and 10% glycerol was used to recover enough binding potential to evaluate the effects of beta h-EP preincubation towards NEM treatment. Preincubation with beta h-EP itself at 0.1-1.0 microM did not result in any increased recovery of opiate binding, in contrast to the findings with the other two ligands.
Westphal
M
M
Hammonds
R G
RG
Ferrara
P
P
Li
C H
CH
D000478:Alkylation; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D003902:Detergents; D004723:Endorphins / Q000494:pharmacology*; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D005033:Ethylmaleimide / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D001615:beta-Endorphin
D003902:Detergents; D004723:Endorphins; D011957:Receptors, Opioid; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D016308:Enkephalin, Leucine-2-Alanine; D005033:Ethylmaleimide