Guanine nucleotide regulation of [125I]beta-endorphin binding to rat brain membranes: monovalent cation requirement.
The binding of [125I]beta h-endorphin to rat brain membranes was investigated in the presence of GTP and guanylyl-5'-imidodiphosphate. In contrast to the binding of the mu-selective opioid agonist, [3H][D-Ala2,MePhe4,Glyol5]enkephalin, and the delta-selective opioid agonist, [3H][D-penicillamine2, D-penicillamine5]enkephalin, [125I]beta h-endorphin binding was not affected by GTP or guanylyl-5'-imidodiphosphate in a concentration-dependent manner in the absence of cations. However, in the presence of NaCl, the inclusion of either GTP or guanylyl-5'-imidodiphosphate resulted in a concentration-dependent inhibition of [125I]beta h-endorphin binding. This inhibition was significantly greater than the decrease in [125I]beta h-endorphin binding observed in the presence of sodium alone. Although GTP most potently inhibited [125I]beta h-endorphin binding in the presence of sodium, inhibition of [125I]beta h-endorphin binding by GTP was also observed in the presence of the monovalent cations lithium and potassium, but not the divalent cations magnesium, calcium, or manganese. The effect produced by GTP in the presence of NaCl was mimicked by GDP, but not by GMP or other nucleotides. Unlike [125I]beta h-endorphin, the binding of the putative sigma receptor agonist, (+)-[3H]SKF 10,047, was not significantly altered by GTP or guanylyl-5'-imidodiphosphate in the absence or presence of sodium.
Selley
D E
DE
Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, NY 14642.
Tyler
C B
CB
Bidlack
J M
JM
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002414:Cations, Monovalent / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000378:metabolism; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008094:Lithium / Q000494:pharmacology; D008297:Male; D010620:Phenazocine / Q000031:analogs & derivatives / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D001615:beta-Endorphin / Q000378:metabolism*
D002414:Cations, Monovalent; D004745:Enkephalins; D006150:Guanine Nucleotides; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D006165:Guanylyl Imidodiphosphate; D012965:Sodium Chloride; D001615:beta-Endorphin; C012134:SK&F 10047; D006160:Guanosine Triphosphate; D020881:Enkephalin, D-Penicillamine (2,5)-; D008094:Lithium; D012964:Sodium; D010620:Phenazocine; D011188:Potassium