Inhibition of neurotensin-stimulated mast cell secretion and carboxypeptidase A activity by the peptide inhibitor of carboxypeptidase A and neurotensin-receptor antagonist SR 48692.
BACKGROUND
Neurotensin (NT), a peptide found in brain and several peripheral tissues, is a potent stimulus for mast cell secretion and its actions are blocked by the specific NT receptor antagonist, SR 48692. Subsequent to stimulation, NT is rapidly degraded by mast cell carboxypeptidase A (CPA). In the experiments described here, we tested for the involvement of CPA activity in the activation of mast cell secretion by the peptide, NT.


METHODS
Mast cells were isolated from the peritoneal and pleural cavities of rats, purified over metrizamide gradients and incubated at 37 degrees C in Locke solution or Locke containing the appropriate inhibitors. For some experiments, media derived from mast cells stimulated by compound 48/80 were used as a source of mast cell CPA activity.


RESULTS
Treatment of mast cells with the highly specific peptide inhibitor of CPA derived from potato (PCI) inhibited histamine release in response to NT and NT8-13 (the biologically active region of NT). This inhibition required some 20 min to develop and was only partially reversed by a 20-min wash period. PCI (10 microM) did not inhibit histamine release in response to NT1-12, bradykinin, compound 48/80, the calcium ionophore, A23187, or anti-IgE serum. PCI also inhibited mast cell CPA activity. SR 48692, a highly selective antagonist of the brain NT receptor and of NT-stimulated mast cell secretion, also inhibited mast cell CPA activity as well as bovine pancreatic CPA activity in a concentration-dependent manner.


CONCLUSIONS
It is suggested that the mast cell binding site for NT and the active site for CPA may share similar characteristics. The results are discussed in terms of NT mechanism of action on the mast cell.
Miller
L A
LA
Department of Biology, Tufts University, Medford, Mass 02155, USA.
Cochrane
D E
DE
Feldberg
R S
RS
Carraway
R E
RE
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors* / Q000187:drug effects*; D043422:Carboxypeptidases A; D006636:Histamine Release / Q000187:drug effects; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism*; D009496:Neurotensin / Q000187:drug effects* / Q000494:pharmacology*; D010940:Plant Proteins / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018028:Receptors, Neurotensin / Q000037:antagonists & inhibitors*; D013997:Time Factors; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D007476:Ionophores; D010940:Plant Proteins; D011480:Protease Inhibitors; D011720:Pyrazoles; D011804:Quinolines; D018028:Receptors, Neurotensin; C079087:SR 48692; D000001:Calcimycin; D009496:Neurotensin; D003189:p-Methoxy-N-methylphenethylamine; D002268:Carboxypeptidases; D043422:Carboxypeptidases A