The binding of somatostatin to rat synaptosomal membranes: effects of detergent solubilisation and of bacitracin.
Specific high and low affinity binding sites for somatostatin have been demonstrated in rat brain synaptosomal membranes using 125I [Tyr"] somatostatin tracer. When incubations were carried out in the presence of low concentrations of bacitracin (0.01% w/v), a 66% increase in association constant of the high affinity binding site to Ka = 1.71 X 10(10) M-1 and a 70% increase in the Ka of the low affinity site to 0.034 X 10(10) M-1 were observed; a similar (50%) increase in the binding capacity of the low affinity site but no increase in the binding capacity of the high affinity site was seen. These results may indicate a direct effect of bacitracin on the membrane that is distinct from its effect as an inhibitor of tracer degradation. The somatostatin-binding capacity of the membranes was solubilised by treatment with Triton X-100 and the apparent molecular weight of the receptor-ligand-detergent micelle complex was estimated by gel filtration to be approximately 250,000.
Weightman
D R
DR
Conlon
J M
JM
Kendall-Taylor
P
P
D000818:Animals; D001414:Bacitracin / Q000494:pharmacology*; D001667:Binding, Competitive / Q000187:drug effects; D003902:Detergents / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D008970:Molecular Weight; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000302:isolation & purification; D017481:Receptors, Somatostatin; D012995:Solubility; D013004:Somatostatin / Q000378:metabolism*; D013501:Surface-Active Agents / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D003902:Detergents; D011956:Receptors, Cell Surface; D017481:Receptors, Somatostatin; D013501:Surface-Active Agents; D001414:Bacitracin; D011092:Polyethylene Glycols; D013004:Somatostatin; D017830:Octoxynol