Increased gall-bladder prostanoid synthesis after bile-duct ligation in the rabbit is secondary to new enzyme formation.
Ligation of the common bile duct (BDL) in the male rabbit resulted in increased gall-bladder microsomal total cyclo-oxygenase activity with prostaglandin E2 (PGE2) and 6-oxoprostaglandin F1 alpha [6-oxo-PGF1 alpha, stable metabolite of prostaglandin I2 (PGI2; prostacyclin)] as the major prostanoids synthesized after 24 and 72 h. Kinetic analysis of gallbladder microsomal membrane fractions incubated with increasing levels of [14C]arachidonic acid indicated that BDL for 24 and 72 h did not change substrate affinity (apparent Km) but markedly increased the rate of conversion (apparent Vmax.) suggesting the presence of more total enzyme responsible for synthesis of 6-oxo-PGF1 alpha and PGE2. BDL for 24 and 72 h significantly increased gall-bladder tissue slice basal release of 6-oxo-PGF1 alpha, but not PGE2, when compared with the controls. Gall-bladder slice release of PGE2 was 3-fold less than 6-oxo-PGF1 alpha in the control gall-bladder slices. Immunoblot analysis of 72 h BDL gall-bladder microsomal membrane fractions showed a slight increase in cyclo-oxygenase content and a 5-fold increase in the content of prostacyclin synthase as compared with the control. These data suggest that the BDL-stimulated total gall-bladder cyclo-oxygenase activity was the result of an increase in the level of specific prostaglandin-synthetic enzymes, in particular prostacyclin synthase, and not from a change in enzyme affinity.
Myers
S
S
Department of Surgery, University of Texas Southwestern Medical Center, Dallas 75235-9031.
Evans
C T
CT
Bartula
L
L
Kalley-Taylor
B
B
Habeeb
A R
AR
Goka
T
T
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001652:Bile Ducts / Q000601:surgery; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005704:Gallbladder / Q000378:metabolism*; D005705:Gallbladder Diseases / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000378:metabolism; D007700:Kinetics; D008026:Ligation; D008297:Male; D008861:Microsomes / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis*; D011817:Rabbits
D011453:Prostaglandins; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D011451:Prostaglandin-Endoperoxide Synthases; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase