Gastric tissue prostaglandin levels. Effect of vagotomy.

To determine tissue prostaglandin levels in antrum and fundus and to examine the effect of vagotomy and distention on tissue prostaglandin levels, truncal and parietal cell vagotomies were performed on rats that were killed at 2, 4, and 6 weeks postoperatively with antral and fundic prostaglandin E1 levels being determined. The fundus has considerably higher levels of prostaglandin than the antrum. No differences after any type of vagotomy however, were noted. It cannot be concluded from this study that increased prostaglandin levels result from vagotomy.     

Dietary lipids,prostaglandin E2 levels,and tooth movement in alveolar bone of rats

Summary A previous study showed that certain dietary lipids can alter arachidonic acid concentrations in alveolar bone. Because arachidonic acid is a precursor of prostaglandin (PG) E₂, which is known to play an important role in orthodontic tooth movement, the purpose of the present study was to determine the effect of dietary lipids on PGE₂ levels and tooth movement. Two groups of male Sprague-Dawley rats (20/group) were fed nutritionally adequate purified diets containing 10% corn oil (group I, rich in n-6 fatty acids) or 9% ethyl ester concentrate of n-3 fatty acids + 1% corn oil (group II rich in n-3 fatty acids). After 5 weeks of feeding the diets, orthodontic force of 56 g was applied to the maxillary incisors to tip them distally. Prior to killing the rats at day 4 and 8 of orthodontic force application, tooth movement was measured by computerized image analysis. Premaxillae were dissected out free of soft tissue and incisors. The alveolar bone was frozen in liquid nitrogen, pulverized, and lipids were extracted. The concentrations of arachidonic acid and fatty acid composition of total phospholipids were measured by gas chromatography. PGE₂ levels were measured by enzyme immunoassay. Arachidonic acid and PGE₂ concentration were significantly lower (P < 0.001) in alveolar bone of rats in group II than in group I. The tooth movement was also significantly lower (P < 0.02) in group II than in group I at both 4 and 8 days. The results suggest that PGE₂ levels in alveolar bone and orthodontic tooth movement can be affected by the type of dietary fat.Presented in part for the Hatton Award Competition at the International Association for Dental Research Meeting, Chicago, Illinois, March 10–14, 1993.     

Increased ex vivo synthesis of prostaglandin E2 by gastric tissue after hemorrhage in rats

Endogenously synthesized prostaglandins are potential mediators of gastrointestinal mucosal protection. Some data suggest that gastric ulceration caused by stressful stimuli is due to diminished mucosal synthesis of prostaglandins. To examine this hypothesis, we determined the effect of hemorrhage, an ulcerogenic stimulus, on ex vivo production of immunoreactive prostaglandin E2 by gastric tissue in the rat. Macroscopic gastric ulcers were reproducibly observed in Sprague-Dawley rats subjected to hemorrhage (3 ml/100 g body weight). The number of ulcers was linearly related to the duration of shock. Prostaglandin E2 synthesis was significantly increased during in vitro incubation of oxyntic and nonoxyntic stomach tissue excised from rats subjected to hemorrhage for 30 minutes (p less than 0.05). These results indicate that damage to the gastric mucosa in rats subjected to hemorrhage occurs despite augmented endogenous secretion of prostaglandin E2. Mechanisms other than impaired prostaglandin biosynthesis were probably responsible for mucosal injury in this model.     

Experimental traumatic brain injury elevates brain prostaglandin E2 and thromboxane B2 levels in rats

Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels were measured in rats following experimental traumatic brain injury. Rats (n = 36) were prepared for fluid percussion brain injury under pentobarbital anesthesia. Twenty-four hours later, rats were lightly anesthetized using methoxyflurane, injured (2.3 atm), and killed 5 or 15 min later. Twelve of the rats died before and are not included in the analyses. The following groups were used for data analysis: group I (n = 6) were sham-injured rats prepared for injury but not injured: group II (n = 6) were injured and killed 5 min later; group III (n = 12) were injured and killed 15 min posttrauma. Thirty seconds prior to sacrifice by decapitation into liquid nitrogen, all rats were injected with indomethacin (3 mg/kg, intravenously [IV]) to prevent postmortem PG synthesis. After sacrifice, brains were removed, weighed, and homogenized in a small quantity of phosphate buffer with indomethacin (50 micrograms/ml). PGE2 and TxB2 levels were determined using double-label radioimmunoassays. Posttraumatic convulsions were observed in 5 of 12 rats in group III and these rats were analyzed separately. PGE2 and TxB2 levels increased significantly (p less than 0.05) in both hemisphere and brainstem 5 min posttrauma. Fifteen minutes after injury, both PGE2 and TxB2 levels remained elevated but the levels were lower than at 5 min in the rats that did not exhibit posttraumatic seizures. This decrease in PG levels at 15 min was not observed in the rats that had seizures after injury and both PGE2 and TxB2 levels remained high in hemispheres and brainstem. Thus, fluid percussion brain injury results in substantial elevations in PGE2 and TxB2 levels and posttraumatic seizures exacerbate the observed increases.     

Elevated tissue factor circulating levels in children with hemolytic uremic syndrome caused by verotoxin-producing E. coli

BACKGROUND: Microvascular thrombosis in the kidney plays an important role in the pathogenesis of hemolytic uremic syndrome (HUS). Tissue factor (TF), present on the vascular surface of endothelial cells, binds factor VIIa. The complex initiates the coagulating cascade by activating factors X and IX. PATIENTS AND METHODS: In cases of HUS associated with verotoxin-producing E. coli (VTEC) infection, VTEC gastroenteritis without HUS and normal controls, we measured plasma concentrations of TF and tissue factor pathway inhibitor (TFPI) to evaluate their clinical significance. In children with non-HUS chronic renal failure (CRF), the TF levels were also measured as another control group. RESULTS: In the acute phase of HUS, plasma levels of TF and TFPI were significantly elevated, then returned to normal range in the recovery phase. The TF levels were closely correlated with the thrombin antithrombin-III complex, a marker of thrombin activity in circulating blood, and with creatinine clearance (Ccr). Furthermore, a positive correlation was noted between plasma TF levels and plasma soluble thrombomodulin (sTM) levels, which is a marker of endothelial cell injury. The influence of decreased excretion from damaged kidneys should be considered since a definite lot correlation was observed between plasma TF levels and Ccr in children with non-HUS CRF. CONCLUSION: From these findings, we concluded that elevated TF circulating levels may also play an important role in blood-clotting activation observed in VTEC-HUS patients, and may also be a useful marker for renal damage.     

Adaptive regulation in skeletal muscle glutamine metabolism in endotoxin-treated rats.

The effects of a single dose of endotoxin (7.5 mg/kg BW) on skeletal muscle glutamine metabolism were studied in vivo in rats to gain further understanding of the altered glutamine metabolism that characterizes sepsis and other catabolic diseases. In endotoxin-treated animals the arterial glutamine concentration fell early initially and then increased compared with control values. Twelve hours after treatment, the arteriovenous concentration difference for glutamine across the hindquarter doubled, resulting in a significant increase in net muscle glutamine release in endotoxin-treated rats. As a consequence, the muscle glutamine concentration fell in the endotoxin-treated animals by 25%-40%, an event that was apparent as early as two hours after endotoxin treatment. Skeletal muscle glutaminase activity, the major enzyme of glutamine breakdown, was unchanged by endotoxemia, but expression of glutamine synthetase mRNA and glutamine synthetase specific activity increased in a time-dependent fashion. The glutamine depletion that develops in skeletal muscle during endotoxemia is caused by accelerated muscle glutamine release rather than an increase in intracellular degradation or a fall in intracellular biosynthesis. The adaptive increase in glutamine synthetase expression that occurs requires de novo RNA and protein synthesis and may be designed to prevent complete depletion of the intracellular glutamine pool.     

The effects of prostaglandin E2 in growing rats: Increased metaphyseal hard tissue and cortico-endosteal bone formation

Summary To assess the efficacy of PGE₂ in inducingin vivo bone formation, graded doses of prostaglandins E₂ were administered to 255 g rats. Histomorphometric analyses of selected sequential fluorescent-labeled bones of rats treated with 0,0.3, 1.0, 3, or 6 mg PGE₂/kg/d for 21 days showed that the doses of PGE₂ depressed longitudinal bone growth, increased growth cartilage thickness slightly, decreased degenerative cartilage cell size and cartilage cell production slightly, and increased proximal tibial metaphyseal hard-tissue mass markedly. Periosteal bone formation was depressed at the higher doses, and an early, slight depression in endosteal bone formation was also observed, along with a striking late increase in endosteal bone formation and in the formation of trabecular bone in the marrow cavity of the tibial shaft. The characteristics and magnitude of these responses were quite similar to those observed in our previous study of the effects of PGE₂ on weanling rats except for the delayed increase in cortico-endosteal bone formation.     

Coordinate control of lipolysis by prostaglandin E2 and prostacyclin in rat adipose tissue.

PGE2 is a potent antilipolytic agent produced by adipose tissue, but its role as a physiological regulator of triglyceride lipolysis is controversial because inhibitors of prostaglandin synthesis have not enhanced hormone-stimulated lipolysis in adipose tissue consistently. Adipose tissue also produces PGI2, but this eicosanoid has not had a demonstrated effect on lipolysis under physiological conditions previously. We investigated both PGE2 and PGI2 production and their effects on lipolysis in rat adipose tissue. We found that 1) EPI-stimulated PGE2 production (like PGI2 production) requires the cooperation of adipocytes and endothelial cells, 2) adipose tissue produces PGE2 and PGI2 at comparable rates, 3) indomethacin inhibits EPI-induced PGE2 and PGI2 production and has no effect on EPI-stimulated lipolysis when added to a mixture of adipocytes and endothelial cells or to intact epididymal fat pads, 4) PGI2 is a potent lipolytic agent when added to isolated adipocytes in the absence of endothelial cells under physiological conditions, 5) the magnitudes and the ED50s of the antilipolytic effect of PGE2 and the lipolytic effect of PGI2 in isolated adipocytes in the absence of endothelial cells are comparable, 6) PGI2 antagonizes the antilipolytic effect of PGE2 in isolated adipocytes in the absence of endothelial cells in a dosage-related manner, and 7) the antilipolytic effect of added PGE2 in isolated adipocytes is greater in the absence of endothelial cells than in their presence, suggesting that endogenous eicosanoid production reduces the effectiveness of added PGE2. These studies demonstrate that catecholamine-induced lipolysis is under the coordinate control of PGE2, a potent antilipolytic agent, and PGI2, a potent lipolytic agent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing the outcome of E. coli peritonitis in rats

Substances that may influence the course and outcome of intra-abdominal sepsis were investigated in an experimental model of Escherichia coli peritonitis in rats. All rats received an intraperitoneal injection of E. coli. In the first set of experiments, substances commonly contaminating the abdominal cavity after trauma were intraperitoneally injected, and the following mortality rates were found: saline solution (controls) 27%, hemoglobin solution 80% (p less than 0.01), whole blood 20% (p greater than 0.05), whole blood together with bile 93% (p less than 0.001) and bile 87% (p less than 0.01). In the second set of experiments, intravenous injection of commonly used solutions gave mortality rates of 20% (controls) for saline solution, 80% for dextran (p less than 0.01) and 47% for Intralipid (p greater than 0.05). E. coli peritonitis in rats thus was aggravated by intraperitoneal hemoglobin, bile or whole blood plus bile, and also by intravenous dextran.     

Decreased hypothalamic prostaglandin D2 and prostaglandin E2 contents during isoflurane anaesthesia in rats

This study was undertaken to evaluate the effect of isoflurane anaesthesia on the hypothalamic contents of both prostaglandin D₂ and E₂ which affect the sleep-wakefulness cycle. Sixty-three Wistar rats were divided into three equal groups, control, iso-flurane and recovery groups. Twenty-one rats of the control did not receive isoflurane. In the other groups 21 rats received isoflurane 2% far 30 min and 21 received isoflurane 2% for 30 min and were allowed to recover their usual behaviours, including righting reflex, spontaneously. The hypothalamus was removed and the contents of PGD₂ and PGE₂ were measured by enzyme immunoassay. The PGD₂ content in the hypothalamus was 397.9 ± 226.0 pg· g^{? 1} for the control group, 134.2 ± 41.2 pg· g^?1 for the isoflurane group and 269.1 ± 124.6 pg · g^?1 for the recovery group, respectively. The hypothalamic PGE₂ contents were 381.4 ± 139.0 pg · g^?1 for the control group, 183.3 ± 26.4 pg · g^?1 for the isoflurane group and 312.2 ± 96.0 pg · g^?1 for the recovery group, respectively. The hypothalamic PGD₂ and PGE₂ contents in the isoflurane group were lower (P < 0.05) than those in the control and recovery groups, while both the PGD₂ and PGE₂ contents of the control and the recovery groups were similar. We conclude that decreased hypothalamic PGD₂ and PGE₂ contents may be related to some manifestations of general anaesthesia with isoflurane.     

Antimicrobial tissue penetration in a rat model of E. coli epididymitis

Following induction of unilateral epididymitis by intratesticular injection of E. coli, a single intraperitoneal dose of amdinocillin, ampicillin, doxycycline, tobramycin, or trimethoprim/sulfamethoxazole was administered to five groups of rats. The animal was sacrificed serially and concentrations of antibiotic in serum, infected epididymides, and non-infected epididymides were determined by high performance liquid chromatography. The ratio of infected to non-infected tissue area under the curve values was 1.05 for trimethoprim, 1.58 for sulfamethoxazole, 1.67 for amdinocillin, 2.01 for tobramycin, 2.25 for doxycycline, and 2.58 for ampicillin. Except for trimethoprim, infected tissue concentrations were significantly greater than compared to uninfected epididymal levels (p less than 0.05). Antibiotic concentrations in infected epididymides compared to serum revealed overall penetration of 34% for amdinocillin, 66% for sulfamethoxazole, 70% for ampicillin, 76% for tobramycin, 256% for trimethoprim, and 257% for doxycycline. In a rat model of epididymitis, trimethoprim and doxycycline demonstrated the greatest degree of epididymal penetration compared to serum. All antibiotics except trimethoprim had significantly greater penetration into infected tissue when compared to non-infected epididymal tissue.     

The role of bone cells in increasing metaphyseal hard tissue in rapidly growing rats treated with prostaglandin E2

The skeletal effects of graded doses of prostaglandin E2 (PGE2) given to weanling Sprague-Dawley rats for 3 weeks were investigated to elucidate the role of bone cells in increasing hard tissue mass. Decalcified (3 micron) sections were quantified in the light microscope by point hit and intersect counting using a Merz grid. Hard tissue mass (bone and calcified cartilage) and osteoblast, osteoclast and osteoprogenitor cell numbers were counted in metaphyseal tissue bands 0.24, 0.48, 0.72, 1.20, 1.68, 2.16, 2.64, 3.12, 3.60 and 4.08 mm from the growth plate metaphyseal junction. Changes were different and more marked in the secondary spongiosa than the primary spongiosa of the proximal tibial metaphysis of treated rats. In the primary spongiosa of rats treated with 3 or 6 mg PGE2/kg/d (1) an increase in bone and hard tissue masses and (2) a decrease in osteoclasts, osteoprogenitor cell numbers and surface to volume ratio was observed. In the secondary spongiosa (lower metaphysis) of rats treated with 2 same dose levels (1) an increase in bone mass, calcified cartilage cores, and hard tissue mass and perimeter, an elevation of osteoprogenitor cell and osteoblast numbers, a depression of osteoclast, osteoclast nuclei numbers and surface to volume ratio and new sites of intramembranous ossification (woven bone formation) originating from the cortico-endosteal envelope was observed. In this growing rat skeletal model, we showed that PGE2 increases metaphyseal calcified tissue mass by depressing hard tissue resorption and stimulating the replication and differentiation of osteoblast precursors to form new foci of woven bone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased bone growth by local prostaglandin E2 in rats

Summary The effects of prostaglandin E₂ (PGE₂) on bone growth were investigated in rats. Daily injection of PGE₂ (1, 10, and 100 pmol) was given via local intraosseous route into the metaphysis of the left tibia for 14 days. The contralateral right tibia injected with vehicle and saline was for the control. The rats receiving no injection provided as normal control. The results obtained indicated that PGE₂ slightly but significantly decreased the body weight increment without effect on tibial length. The most prominent effect of PGE₂ was the increase of metaphyseal bone trabeculae by 45–81% in a dose-dependent manner. The microscopic examination revealed that PGE₂ unequivocally increased the new woven bone formation. The bone cell population study showed no difference between the number of osteoblasts and osteoclasts in primary spongiosa of the PGE₂-injected limbs and those of contralateral limbs. However, the numbers of osteoblasts and osteoclasts were markedly increased in secondary spongiosa in the PGE₂-injected limbs. This finding confirmed a stimulatory role of PGE₂ in the bone formation. The local intraosseous injection of PGE₂ was proven to be a good model for the study of local growth factors on bone metabolism with a lower effective dose which eliminates the systemic side effects.     

The effects of prostaglandin E2 in rapidly growing rats: depressed longitudinal and radial growth and increased metaphyseal hard tissue mass

The effects of 0, 0.3, 1.0, 3.0, or 6.0 mg of prostaglandin E2 (PGE2)/kg/day administered subcutaneously for 3 weeks to triple fluorochrome-labeled weanling rats are reported. Microradiographs and undecalcified sections of proximal tibiae, tibial shafts, and seventh caudal vertebrae were evaluated by static and dynamic bone histomorphometry techniques. Significant changes were observed only at higher dose levels. Proximal tibial longitudinal growth rates were depressed in doses of 1, 3, or 6 mg PGE2/kg/day. Growth plate thickness and the size of hypertrophic cartilage cells were decreased in animals given 3 and 6 mg of PGE2/kg/day, but the calculated rate of cartilage cell production was unaffected. At doses of 6 mg PGE2/kg/day, periosteal bone apposition rates between Day -1 and Day +19 in both the tibial shafts and caudal vertebral cortices were depressed by less than 25%. Cortical bone mass and endosteal bone apposition rates in the tibial shaft and caudal vertebrae were unaffected. Hard tissue mass in the secondary spongiosa of the proximal tibial metaphysis increased dramatically (28%, 44%, and 60%, respectively) in rats treated with 1, 3, or 6 mg PGE2/kg/day. In addition, the secondary spongiosa contained numerous islands of woven trabecular bone along with an increased number of trabeculae. The study demonstrates that high doses of PGE2 stimulate new woven trabecular bone production and depress longitudinal and radial growth in rapidly growing rats.     

The effect of tenoxicam on intraperitoneal adhesions and prostaglandin E2 levels in mice

We determined whether tenoxicam administered intraperitoneally in the preoperative period had an effect on the development of postoperative intraabdominal adhesions (IAA). For this purpose, 100 albino mice were divided into four random groups. Mice in Group 1 were given only 1 mL of 0.9% NaCl intraperitoneally, whereas in Group 2, 1 mL of tenoxicam (150 microg = 5 mg/kg) was administered. After the induction of anesthesia, a median laparotomy was performed, and the bowels were traumatized by touching them with powdered gloves before the incision was closed in Groups 3 and 4. Intraperitoneal tenoxicam was administered to mice in Group 4 after skin closure. All mice were killed after 14 days to determine macroscopic and microscopic IAA; prostaglandin E2 levels were also measured. Postoperative evaluation revealed a reduced IAA formation and a parallel decrease in tissue prostaglandin E2 levels in Group 1 and 2 mice. We conclude that intraperitoneal tenoxicam decreased IAA formation with no peritoneal reaction in the postoperative period. Implications: Postoperative intraabdominal adhesions can cause intestinal obstruction, pelvic pain, or infertility. In this study, we showed that intraperitoneally administered tenoxicam decreases tissue prostaglandin E2 levels and intraabdominal adhesions in mice.     

Role of spinal cyclooxygenase-2 and prostaglandin E2 in fentanyl-induced hyperalgesia in rats

Background

Accumulated evidence suggests that spinal cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) may be implicated in the development of opioid-induced hyperalgesia.