Regional distribution and biochemical properties of 125I-Tyr8-substance P binding sites in synaptic vesicles.
1. Binding of 125I-Tyr8-substance P (SP) to synaptic vesicles shows an uneven distribution within the brain and the spinal cord. The regional distribution has a positive correlation with the SP-content, except in the hypothalamus. 2. Ca2+ and MG2+-ions (1 and 10 mM) decrease the number of binding sites without alteration of affinity. EDTA and EGTA enhance SP-binding which is interpreted as being due to removal of the inhibitory influence of endogenous Ca2+ and Mg2+ through chelation with these agents. No significant inhibition of SP binding was observed by Na+ or K+ in concentrations below 100 mM. 3. Pretreatment of synaptic vesicles with trypsin or with phospholipase A2, C and D leads to a total loss of SP binding showing a proteolipid or a joint protein-phospholipid nature of these binding sites. SH groups do not contribute to SP binding since no effect of N-ethylmaleimide and monoidoacetic acid on SP binding was found.
D000818:Animals; D001665:Binding Sites; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013373:Substance P / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*
D011506:Proteins; D013438:Sulfhydryl Compounds; D010758:Phosphorus; D013373:Substance P