Sex differences in gallbladder prostaglandin synthesis mediated by acute inflammation

Cytokines inhibit sexual behavior in female rats: II. Prostaglandins mediate the suppressive effects of interleukin-1beta

The proinflammatory cytokine interleukin-1 (IL-1) induces several behavioral alterations that are characteristic of illness, such as anorexia and reduced locomotor and social activity. We have recently demonstrated that IL-1 inhibits sexual activity, motivation and attractivity in female, but not in male rats following either central or peripheral administration. In the present study we examined the involvement of prostaglandin (PG) synthesis in mediating IL-1-induced suppression of female sexual behavior. Administration of the cyclooxygenase blockers indomethacin or ibuprofen completely prevented IL-1-induced suppression of female sexual behavior, including the reduction in proceptive behavior, the lordosis response to a male's mounts, and the preference for a sexually active partner. In a subsequent study, ex-vivo release of hypothalamic PGE2 and the secretion of corticosterone (CS) were measured in males and estrous females following IL-1 administration. At the same time and dose of IL-1 administration that significantly reduced sexual behavior in female but not male rats, IL-1 produced a significant increase in PGE2 release in female, but not in male rats. In contrast, IL-1 induced a significant elevation of serum CS levels in males but not in females. These findings suggest that PG synthesis is involved in mediating the effects of IL-1 on female sexual behavior. Furthermore, differential secretion of PGs and CS may underlie the gender difference in the effects of IL-1 on sexual behavior.

Acute cholecystitis potentiates bradykinin stimulated fibroblast prostanoid release in the rabbit

Gallbladder explants from control rabbits and rabbits subjected to bile duct ligation (BDL) for 24 and 72 h (cholecystitis model) were placed in cell culture to determine the source for increased gallbladder prostanoid synthesis during cholecystitis. Cultures from control and 24 h BDL gallbladders grew spindle shaped fibroblasts which did not exhibit increased prostanoid synthesis. 72 h BDL gallbladder cell cultures grew large polygonal shaped cells which appeared to be 'stimulated fibroblasts' by light and electron microscopy and were associated with increased basal and bradykinin stimulated 6-keto-PGF1 alpha release and increased content of prostacyclin synthase when measured by enzyme immunoassay and protein immunoblot analysis respectively. Use of bradykinin antagonists showed that the bradykinin BK2 subtype receptor was the most prominent in the 72 h BDL cell cultures. The 'stimulated fibroblasts' were the source of bradykinin stimulated gallbladder 6-keto-PGF1 alpha synthesis in the inflamed rabbit gallbladder which was mediated by the bradykinin B2 subtype receptor.

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.

Bradykinin and not cholecystokinin stimulates exaggerated prostanoid release from the inflamed rabbit gallbladder

The relationship of bradykinin and cholecystokinin (CCK) to inflamed gallbladder prostanoid synthesis and release was examined in rabbits treated with common bile duct ligation (BDL) for 24 or 72 h. Gallbladders removed from control and BDL groups were incubated in oxygenated Krebs buffer at 37 degrees C (pH 7.4) for 60 min. The slices were then placed every 20 min in vials containing increasing doses of bradykinin (30-3000 ng) or CCK (30-1000 ng). Incubation fluid was analyzed by RIA for 6-keto-prostaglandin (PG)F1 alpha (PGI2 metabolite), PGE2 and thromboxane (TX) B2. Bradykinin stimulated control gallbladder 6-keto-PGF1 alpha and PGE2 release was modest. Gallbladders from 24- and 72-h BDL groups released 3- to 10-fold higher levels of 6-keto-PGF1 alpha and PGE2 (not TXB2) following bradykinin stimulation when compared to controls, which was abolished with indomethacin pretreatment. CCK did not stimulate gallbladder prostanoid release in the control or BDL groups. These data show that bradykinin and not CCK stimulated PGI2 and PGE2 release from inflamed rabbit gallbladder. Increased BDL gallbladder PGI2 release may be prolonged or augmented by bradykinin as gallbladder distention and progressive acute inflammation stimulate local bradykinin formation.

The role of eicosanoids in experimental and clinical gallbladder disease

The mammalian gallbladder has been shown by many authors to synthesize and release arachidonic acid metabolites. Many factors influence gallbladder eicosanoid release including sex of the animal, neural influences, age of the animal, pathologic stimuli (gallstones, inflammation), chemical mediators, hormones and the presence of hypercholesterolemia. The net result of these factors is release of gallbladder eicosanoids which act as paracrine substances to influence the gallbladder physiologic functions of water transport and motility. This review examines the experimental in vivo and in vitro experimental studies that have examined the various factors that alter mammalian gallbladder eicosanoid release in normal and pathologic states.