G Polities | PubMed Health

PubMed1994

Effect of platelet-activating factor and its antagonists on colonic dysmotility and tissue levels of colonic neuropeptides.

We investigated whether platelet-activating factor (PAF) alters colonic tissue levels of substance P and vasoactive intestinal peptide (VIP), two neuropeptides that regulate colonic motility. Left colons were harvested from NZ White Rabbits and underwent vascular perfusion via the inferior mesenteric artery. Strain gauge transducers were sewn onto the serosal surface of the colon to evaluate colonic motility. Colons were perfused with either buffered saline alone or with 5.0 x 10(-5) M PAF. PAF administration increased tissue VIP and substance P levels and decreased the force of colonic contractions. Pretreatment with WEB-2170 or alprazolam decreased concentrations of both tissue neuropeptides, and decreased the force of colonic contractions and minute motility index. These results suggest that both VIP and substance P are stimulated by PAF and may participate in colonic dysmotility during inflammatory states.

Alprazolam↗

PubMed1994

Platelet-activating factor mediates trinitrobenzene induced colitis.

Platelet-activating factor (PAF) is an endogenous phospholipid which may be an important mediator of shock and inflammation. Recent evidence suggests that PAF plays a role in the development of ischemic colitis and inflammatory bowel disease. Its effects are mediated by second messengers, including the arachidonic acid metabolites. Using an ex vivo isolated left colon rabbit perfusion model, our aims were to determine whether exogenously administered trinitrobenzene sulfonic acid (TNB), which produces experimental colitis, stimulates both PAF and eicosanoid release in the colon, and if so, whether this effect can be blocked by a PAF antagonist. Colonic inflammation was induced by the intracolonic administration of 0.25 ml of 50% ethanol containing 30 mg of TNB. Tissue and perfusate concentrations of the eicosanoids, [prostaglandin E (PGE2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2), leukotriene B4 (LTB4)] and the autocoid PAF were measured by ELISA. During TNB infusion there was a significant increase in tissue levels of PAF compared to control colons. Additional studies performed pretreating the colons with the PAF receptor antagonist WEB-2170 prior to TNB infusion blocked PAF release. TNB stimulated release of luminal eicosanoids except LTB4 and suppressed release of tissue prostanoids. Pretreatment with WEB-2170 prior to TNB inhibited luminal eicosanoids, and inhibited PGE2 and prostacyclin, but not TX tissue suppression. Inhibition of TNB-stimulated PAF release by WEB-2170 suggests that PAF may play a role in TNB-induced colitis and this phenomenon may mediate tissue injury.

6-Ketoprostaglandin F1 alpha↗