A molecular weight study of the rat brain delta opioid receptor.

The molecular weight of the rat brain delta opioid receptor, studied with antiidiotypic antibodies to anti-leucine enkephalin that mimic leucine enkephalin in binding to the receptor, was examined by molecular sieving and Western Blots under nondenaturing, denaturing and reducing conditions. The receptor appeared to be 55-65 kDa, which on solubilization may exist in equilibrium with receptor oligomers of 130-150 kDa and aggregates of > 200 kDa. These forms may also represent aggregation due to solubilization. A 38-43 kDa molecule was considered a minor form of the receptor in the brain.

Ontogeny, glycosylation and modulation by dialysis, sodium and nucleotides of the rat brain delta opioid receptor studied with anti-idiotypic antibodies to anti-leucine enkephalin.

Ontogeny of the rat brain delta opioid receptor in 1-60 days old animals has been studied with anti-idiotypic antibodies to anti-leucine enkephalin. It is found that delta opioid receptors are present in rats from birth and attain adult levels by 28 days and these receptors are glycosylated and inhibited by Na+, GTP, ATP and CTP at all ages. Adult membrane-bound and solubilized delta opioid receptors are inhibited to similar extents by Na+ (100 mM), GTP, ATP and CTP (50 microM). Dialysis of the adult membrane-bound receptor led to 81% loss in binding which was restored by 100 mM Na+, 50 microM GTP, ATP and CTP to 77, 72, 87 and 94% respectively and by 100 mM NH4+, Mg2+, Ca2+ and Mn2+ to 63, 43, 57 and 73% respectively. Dialysis of the solubilized receptor resulted in 23% loss in binding with Na+ (100 mM), GTP and ATP (50 microM) inhibiting receptor binding to 46, 62 and 54% respectively, while CTP (50 microM) restored binding to 88%. These studies indicate that the delta opioid receptor can be probed with anti-idiotypic antibodies to anti-leucine enkephalin, that functional, glycosylated receptors are present at birth in rats and that the adult membrane-bound and solubilized receptors are modulated differently by dialysis.

Immunohistochemical mapping of rat brain delta opioid receptor.

Delta opioid receptors were immunohistochemically mapped in the rat brain with anti-idiotypic antibodies to anti-leucine enkephalin specific for the receptor. Regions of highest receptor binding were in the cerebral cortex and caudate putamen Lower receptor binding was mapped to the hypothalamus and claustrum.

The rat brain delta opioid receptor studied with anti-idiotypic antibodies to anti-leucine enkephalin.

Anti-idiotypic antibodies to anti-leucine enkephalin raised in rabbits immunized with leucine enkephalin conjugated to BSA, were purified and characterized for their ability to mimic leucine enkephalin in binding to the rat brain delta opioid receptor. An ELISA was standardized to assay the delta opioid receptor using these antibodies. The rat brain receptor was purified to 308 fold with a yield of 1.5% using these antibodies for assay. The receptor, probed with these anti-idiotypic antibodies, was characterized with respect to binding parameters, molecular weight and effect of divalent cations.