Enhanced bradykinin-stimulated prostaglandin release in the acutely inflamed guinea pig gallbladder is due to new synthesis of cyclooxygenase 1 and prostacyclin synthase.
BACKGROUND
Our previous studies have shown that acute gallbladder (GB) inflammation increases endogenous bradykinin (BK)-stimulated prostaglandin (PG) release and inhibits guinea pig (GP) GB contractility. This study examines the hypothesis that exaggerated PG release following BK stimulation in the inflamed guinea pig GB is due to new protein synthesis of cyclooxygenase 1 (COX-1) and prostacyclin synthase (PS).


METHODS
Male Hartley GPs (450-550 g) were anesthetized and underwent common bile duct ligation (BDL, a model of acute inflammation). GBs were harvested after 3 days from BDL and control groups. Tissue slices were prepared and placed in oxygenated tissue culture medium at 37 degrees C for 1 h (basal) and for a second hour in medium alone (carrier, Car), medium plus 10(-6) M BK, or medium plus 10(-6) M BK plus cycloheximide 100 microgram/ml (BK + CX). The medium was assayed for net release of 6-keto-PGF1alpha (PGI2 metabolite), thromboxane B2 (TxB2), PGE2, leukotriene B4 (LTB4), and C4 (LTC4) by enzyme immunoassay and data are reported as nanograms per milligram of protein. GB tissue from control and BDL groups was examined for COX-1, COX-2, PS, and inducible nitric oxide synthase (iNOS) content by Western blot analysis, analyzed by densitometry, and reported as densitometry units.


RESULTS
All data were analyzed by ANOVA and t test and reported as means +/- SEM, N >/= 5.BK increased the release of PGI2 and PGE2 from the control group and markedly exaggerated release of PGI2 and PGE2 from the BDL GP gallbladder. This exaggerated PGI2 and PGE2 release was greatly diminished by inhibition of new protein synthesis with cycloheximide. TxB2, LTB4, and LTC4 showed no significant differences between any groups. COX-1 and PS contents were significantly elevated in the BDL group compared with control. COX-2 and iNOS were not present in control or BDL GBs.


CONCLUSIONS
These data suggest that the enhanced BK-stimulated PG release seen in the acutely inflamed GP gallbladder is due to the synthesis of new COX-1 and PS enzymes.
Bogar
L J
LJ
Department of Surgery, Temple University School of Medicine, Philadelphia, Pennsylvania, USA.
Bartula
L L
LL
Parkman
H P
HP
Myers
S I
SI
D000208:Acute Disease; D000818:Animals; D015153:Blotting, Western; D001920:Bradykinin / Q000494:pharmacology*; D051545:Cyclooxygenase 1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D015777:Eicosanoids / Q000378:metabolism; D005705:Gallbladder Diseases / Q000378:metabolism*; D006168:Guinea Pigs; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D007249:Inflammation / Q000378:metabolism; D019746:Intramolecular Oxidoreductases / Q000096:biosynthesis*; D007527:Isoenzymes / Q000096:biosynthesis*; D008297:Male; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D011453:Prostaglandins / Q000378:metabolism*
D015777:Eicosanoids; D007527:Isoenzymes; D011453:Prostaglandins; D003577:Cytochrome P-450 Enzyme System; D051545:Cyclooxygenase 1; D011451:Prostaglandin-Endoperoxide Synthases; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase; D001920:Bradykinin