thromboxane-a2 and Atrophy

Cell culture models implicate increased nitric oxide (NO) synthesis as a cause of mucosal hyperpermeability in intestinal epithelial infection. NO may also mediate a multitude of subepithelial events, including activation of cyclooxygenases. We examined whether NO promotes barrier function via prostaglandin synthesis using Cryptosporidium parvum-infected ileal epithelium in residence with an intact submucosa. Expression of NO synthase (NOS) isoforms was examined by real-time RT-PCR of ileal mucosa from control and C. parvum-infected piglets. The isoforms mediating and mechanism of NO action on barrier function were assessed by measuring transepithelial resistance (TER) and eicosanoid synthesis by ileal mucosa mounted in Ussing chambers in the presence of selective and nonselective NOS inhibitors and after rescue with exogenous prostaglandins. C. parvum infection results in induction of mucosal inducible NOS (iNOS), increased synthesis of NO and PGE2, and increased mucosal permeability. Nonselective inhibition of NOS (NG-nitro-L-arginine methyl ester) inhibited prostaglandin synthesis, resulting in further increases in paracellular permeability. Baseline permeability was restored in the absence of NO by exogenous PGE2. Selective inhibition of iNOS [L-N6-(1-iminoethyl)-L-lysine] accounted for approximately 50% of NOS-dependent PGE2 synthesis and TER. Using an entire intestinal mucosa, we have demonstrated for the first time that NO serves as a proximal mediator of PGE2 synthesis and barrier function in C. parvum infection. Expression of iNOS by infected mucosa was without detriment to overall barrier function and may serve to promote clearance of infected enterocytes.

Topics: Animals; Animals, Newborn; Atrophy; Cryptosporidiosis; Cryptosporidium parvum; Diarrhea; Dinoprostone; Eicosanoids; Epoprostenol; Ileum; Intestinal Mucosa; Microscopy, Electron; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Prostaglandins; Reverse Transcriptase Polymerase Chain Reaction; Sodium; Swine; Thromboxane A2

Topics: Adaptation, Physiological; Animals; Atrophy; Epoprostenol; Female; Gastric Mucosa; Prostaglandins E; Rats; Rats, Inbred Strains; Thromboxane A2

The development of hydronephrotic atrophy as measured by dry and wet weight in relation to wholebody weight, in rats after complete unilateral ureteral obstruction could be influenced by oral administration of OKY 1581, an inhibitor of thromboxane A2 synthesis. The data are consistent with the thesis that preglomerular thromboxane A2-mediated active vasoconstriction is involved, most likely by ischemia, in the development of hydronephrotic atrophy, at least in the renal cortex.

Topics: Animals; Atrophy; Female; Hydronephrosis; Kidney Cortex; Kidney Medulla; Methacrylates; Rats; Thromboxane A2; Ureteral Obstruction