An inhibitor of endopeptidase-24.15 blocks the degradation of intraventricularly administered dynorphins.
Conversion of the octapeptide dynorphin (Dyn) A-(1-8) to Leu5-enkephalin (LE) by endopeptidase EC 3.4.24.15 (EP-24.15) in vivo was examined using the technique of ventriculocisternal perfusion. Peptides were administered intracerebroventricularly in the presence or absence of the EP-24.15 inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Phe-p-aminobenzoate (cFPAAF-pAB) via cannulae placed into the lateral ventricle of urethane-anesthetized rats. The concentration of Dyn-like peptides and LE within the CSF was monitored by radioimmunoassay in samples of CSF taken from a second cannula placed in the cisterna magna. In the absence of inhibitor, less than 5% of the Dyn A-(1-8) administered was recovered in CSF. Immunoreactive LE, which is normally not found in CSF, increased rapidly in content following Dyn A-(1-8) infusion, an observation suggesting that the larger peptide is converted to LE. When the inhibitor cFPAAF-pAB was coadministered with Dyn A-(1-8), the concentration of immunoreactive Dyn A-(1-8) after 5 min was 40 times higher than that found in the absence of inhibitor. The angiotensin converting enzyme inhibitor captopril reduced the degradation of Dyn A-(1-8) to a much lesser degree. The inhibitor of EP-24.15 also afforded some protection of other Dyn-like peptides. No EP-24.15 activity was found in rat CSF, whereas high activity was found in the choroid plexus. Taken together, these data clearly indicate that an ectoenzyme form of EP-24.15 rapidly converts intracerebroventricularly administered Dyn-like peptides to LE.
Molineaux
C J
CJ
Department of Pharmacology, Mount Sinai School of Medicine, CUNY 10029.
Ayala
J M
JM
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002216:Captopril / Q000494:pharmacology; D002552:Cerebral Ventricles; D002831:Choroid Plexus / Q000201:enzymology; D004399:Dynorphins / Q000008:administration & dosage / Q000134:cerebrospinal fluid*; D004743:Enkephalin, Leucine / Q000134:cerebrospinal fluid; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000134:cerebrospinal fluid*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
D009842:Oligopeptides; D010446:Peptide Fragments; C064939:N-(1-carboxy-3-phenylpropyl)-alanyl-alanyl-phenylalanine-4-aminobenzoate; D004743:Enkephalin, Leucine; D004399:Dynorphins; C026770:dynorphin (1-8); D002216:Captopril; D007703:Peptidyl-Dipeptidase A; D008666:Metalloendopeptidases; D015260:Neprilysin; C022510:thimet oligopeptidase; D007930:Leucine; C012211:ubenimex