Alterations of intracellular oxidative metabolism as stimuli evoking prostaglandin biosynthesis

Human decidua and uterine contractility

Physiological saline solution injected into the uterus by the extraamniotic route was found to damage the decidua and rupture its lysosomes. The mechanism by which this procedure provokes abortion may be through the release of lysosomal phospholipase A2 (EC 3.1.1.4), an enzyme thought to regulate the formation of polyunsaturated fatty acids utilized for prostaglandin synthesis. A similar sequence of events may be involved in the initiation of spontaneous labour, since decidual cells obtained at elective Caesarean section at term exhibited degenerative changes and signs of release of a lysosomal marker enzyme. The cause of this release is unknown.

Fever: causes and consequences

The present review distinguishes pathogenic, neurogenic, and psychogenic fever, but focuses largely on pathogenic fever, the hallmark of infectious disease. The data presented show that a complex cascade of events underlies pathogenic fever, which in broad outline - and with frank disregard of contradictory data - can be described as follows. An invading microorganism releases endotoxin that stimulates macrophages to synthesize a variety of pyrogenic compounds called cytokines. Carried in blood, these cytokines reach the perivascular spaces of the organum vasculosum laminae terminalis (OVLT) and other regions near the brain where they promote the synthesis and release of prostaglandin (PGE2). This prostaglandin then penetrates the blood-brain barrier to evoke the autonomic and behavioral responses characteristic of fever. But then once expressed, fever does not continue unchecked; endogenous antipyretics likely act on the septum to limit the rise in body temperature. The present review also examines fever-resistance in neonates, the blunting of fever in the aged, and the behaviorally induced rise in body temperature following infection in ectotherms. And finally it takes up the question of whether fever enhances immune responsiveness, and through such enhancement contributes to host survival.

Abnormalities in the biosynthesis of thromboxane A2 and prostacyclin in children with cyanotic congenital heart disease

BACKGROUND

Children with cyanotic congenital heart disease and pulmonary outflow tract obstruction have shortened platelet survival times and are susceptible to thrombosis and organ infarction. Thromboxane A2 and prostacyclin have opposing actions on platelet aggregability and an imbalance in their biosynthesis might contribute to the pathophysiology of these complications.

METHODS

Biosynthesis of thromboxane A2 and prostacyclin was investigated in 16 children (4-32 months, median 18 months) with cyanotic congenital heart disease and pulmonary outflow tract obstruction and compared with 16 healthy children of a similar age (6-34 months, median 24 months). Urinary excretion of 2,3-dinor-thromboxane B2 (a metabolite of thromboxane A2) and of 2,3-dinor-6-oxo-prostaglandin F1 alpha (a metabolite of prostacyclin) was measured.

RESULTS

The children with cyanotic congenital heart disease and pulmonary outflow tract obstruction excreted more 2,3-dinor-thromboxane B2 than the healthy children: 916(163) compared with 592(122) ng/g creatinine (mean(SEM); 2p = 0.014). The ratio of excretion of 2,3-dinor-thromboxane B2 to 2,3-dinor-prostaglandin F1 alpha was greater in the patients than in the healthy control group (2.38(0.28) v 1.3(0.22)) (2p = 0.002).

CONCLUSION

The balance between biosynthesis of prostacyclin and of thromboxane A2 is abnormal in children with cyanotic congenital heart disease and pulmonary outflow tract obstruction and favours platelet aggregation and vasoconstriction.

The association of lipid abnormalities with tissue pathology in human osteoarthritic articular cartilage

Articular cartilage is one of very few body tissues uniquely characterized as having substantial stores of lipid deposits. Lipid droplets are naturally accumulated by chondrocytes and individual fatty acids have been shown to have protective as well as deleterious effects on cartilage degradation in animal models of degenerative joint disease. As a means to better assess the role of lipids in human joint pathology, a comparative analysis of fatty acids was undertaken in small segments of osteoarthritic articular cartilage. The data were assessed in terms of chondrocyte synthetic activity and histological determination of disease severity. The distribution profile of individual fatty acids in normal and osteoarthritic specimens remained constant, with palmitic, oleic, and linoleic acids representing 85% of the total fatty acids. In contrast, levels of total fatty acids were markedly increased in association with increasing degree of lesion severity. Compared with tissue from normal-aged joints, grade 0 to 1 mild lesions had elevated levels of total fatty acids, essential fatty acids, and chondrocyte synthetic activity of 80%, 312%, and 393%, respectively. More severe tissue involvement (grade 6 to 9), was associated with even greater increases of 440%, 1,100%, and 1,150%, respectively. No change was noted in cholesterol content in any tissue. The accumulation of arachidonic acid was greater than the proportional increase in total fatty acid content and was primarily distributed into the neutral lipid fraction, where it constituted almost 62% of the fatty acid level in tissues of moderate lesion severity. There was an association of lipid accumulation in general and arachidonic acid in particular with histological severity.(ABSTRACT TRUNCATED AT 250 WORDS)

Subthreshold argon-laser irradiation elicits a pronounced vitreal prostaglandin E2 response

Chorioretinal production of prostaglandin type E2 (PGE2) as well as changes in vitreal protein and PGE2 concentrations were studied following retinal irradiation with low-power laser energy that caused ophthalmoscopically invisible ("subthreshold") laser burns. This was compared with changes following ophthalmoscopically visible ("suprathreshold") laser burns. Our results demonstrate that with in eyes exposed to the lower-power levels, the enhancement in vitreal PGE2 concentration persisted for a longer period and was more pronounced than in eyes exposed to the suprathreshold levels (a 3-fold and a 2-fold increase above baseline values, respectively). Protein leakage into the vitreous was noted only in the suprathreshold group, indicating a blood-retinal barrier (BRB) disruption. The findings of persistent, excessive PGE2 vitreal levels with no protein leakage in the subthreshold group suggest a possible anti-inflammatory role for PGE2 following low-power laser exposure.

The interaction between oxygen and vascular wall

In vascular strips of canine carotid arteries stepwise lowering of oxygen tension from hyperoxic levels of 550 mmHg to 20 mmHg caused in preparations with endothelium a dose-dependent hyperpolarization and relaxation of smooth muscle cells when oxygen tensions between approximately 150 mmHg and 35 mmHg were attained. Pronounced hypoxia with oxygen tensions below 30 mmHg induced a depolarisation and an increase in force generation. During comparable investigations on vessel preparations without endothelium only a slight hyperpolarization and relaxation of the smooth muscle were observed when decreasing the oxygen tension from 550 mmHg to approx. 35 mmHg. In the presence of indomethacin (10(-5) M) a small but significant reduction in the hypoxia-induced hyperpolarization and decrease in smooth muscle tone was found in intact vascular strips with endothelium. Depolarisation and contraction occurred at oxygen tensions below approx. 50-60 mmHg.

Chemiluminescence in human whole blood: modulation by the cocarcinogens phorbol diester and polychlorobiphenyls

A human whole blood chemiluminescence (CL) assay was established using zymosan as cell activator. Aroclor 1254 was found to inhibit this CL response in a direct linear relation to its concentration, (50% inhibitory dose, (ID50) equal to 5 x 10(-4)M) in diluted blood samples of 10 normal human subjects. In comparison the ID50 of other inhibitors was 1.3 x 10(-3)M for ethylenediamine tetraacetic acid, 3.3 x 10(-3)M for ascorbic acid, 4 x 10(-3)M for reduced glutathione, 1.2 x 10(-1)M for ethanol, 2.5 x 10(-1)M for methanol and 3.7 x 10(-1)M for dimethyl sulfoxide. Using 12-o-tetradecanoyl-phorbol-13-acetate (TPA) as cell activator the CL response was likewise inhibited by Aroclor 1254 with an ID50 of 4.5 x 10(-4)M. However, it was found that Aroclor 1254 alone has a stimulatory CL effect on otherwise unactivated cells. To compare the mechanisms involved in the CL elicited by the three stimulants zymosan, TPA and Aroclor 1254, the CL signal was measured in the presence of cytochalasin B. Cytochalasin B inhibited zymosan-induced CL, had a smaller inhibitory effect on TPA-induced CL but it could augment the CL response initiated by Aroclor 1254. This pattern of responses implicates Aroclor 1254 in the activation of eicosanoid metabolism as it matches the differential responses reported for arachidonic acid.

Effect of PO2 on prostaglandin E2 production in renal cell cultures

There is evidence both from in vivo and in vitro studies which suggests that hypoxia stimulates the synthesis of prostanoids in some tissues. In the present study, the in vitro production of prostaglandin E2 (PGE2) was studied in three different renal cell lines incubated at various PO2 values between 143 and 3 mm Hg for 24 h. In rat kidney mesangial cell cultures, PGE2 production increased up to 99 ng PGE2/mg protein at 7 mm Hg O2, compared to 52 ng/mg at 143 mm Hg O2, but was lowered at 26 ng/mg at 3 mm Hg O2. PGE2 production by the pig kidney tubule cell lines LLC-PK1 and PK-15 was insensitive to PO2 changes. Because PGE2 production is known to be Ca2+-dependent and was indeed stimulated by the Ca-ionophore A 23187, effects of hypoxia on 45Ca2+-fluxes were also studied. In none of the 3 cell lines, net 45Ca-influx was altered after incubation at low PO2. However, net 45Ca-efflux increased during hypoxic incubation of mesangial cells possibly as a result of intracellular Ca-mobilization. These results indicate that hypoxia stimulates PGE2 synthesis in mesangial but not in tubule cell cultures. However, at very low PO2 values, or anoxia, the formation of cyclic endoperoxides from arachidonic acid may be lowered. Since mesangiocytes are smooth muscle-like cells, the hypoxia-induced synthesis of relaxing prostanoids could play a role in the regulation of smooth muscle tone.

Studies on the mechanism of carbon monoxide-induced vasodilation in the isolated perfused rat heart

We investigated the effects of dissolved CO on isolated potassium-arrested (K+) perfused rat hearts. Hearts from male Sprague-Dawley rats were perfused via the aorta with oxygenated Krebs-Henseleit solution containing 20 mM K+. Coronary flow (Qt) averaged 48.8 +/- 1.6 (SE), 48.1 +/- 1.7, and 55.6 +/- 1.7 ml/min/g dry wt when the perfusate was equilibrated with 95% O2-5% CO2, 5% N2-90% O2-5% CO2, and 5% CO-90% O2-5% CO2, respectively. The change in Qt was statistically significant when CO was present in the perfusion medium, but was not significant when N2 was present. Furthermore, the effect was reversible because coronary flow returned to control levels when CO was removed. Myocardial oxygen consumption (MVO2) did not change significantly when hearts were perfused with either N2 or CO. The magnitude of CO-induced vasodilation was not affected significantly by the addition of either 5 microM propranolol, 2 microM phentolamine, 1 unit of adenosine deaminase, or 0.1 mM indomethacin to the perfusate. In addition, CO reversed the vasoconstrictive effects of the alpha-agonist methoxamine. These results indicate that CO exerts a vasodilatory effect on coronary vasculature that is not the result of decreased O2 content in the perfusate and is not mediated by adrenergic influences, adenosine, or prostaglandins.

Hypoxia enhances prostaglandin synthesis in renal mesangial cell cultures

In view of recent findings which suggest that renal prostaglandins mediate the effect of hypoxia on erythropoietin production, we have studied whether hypoxia is a stimulus for in vitro prostaglandin synthesis. Studies were carried out in rat renal mesangial cell cultures which produce erythropoietin in an oxygen-dependent manner. Production rates of PGE2 and in specified samples also of 6-keto-PGF1 alpha, as a measure of PGI2, and PGF2 alpha were determined by radioimmunoassay after incubation at either 20% O2 (normoxic) or 2% O2 (hypoxic) in gas permeable dishes for 24 hrs. Considerable variation in PGE2 production was noted among independent cell lines. PGE2 production appeared to be inversely correlated to the cellular density of the cultures. In addition, PGE2 production was enhanced in hypoxic cell cultures. The mean increase was 50 to 60%. PGF2 alpha and 6-keto-PGF1 alpha increased by about the same rate. These results indicate that hypoxia is a stimulus for in vitro prostaglandin production.

Free fatty acids and energy metabolites in ischemic cerebral cortex with noradrenaline depletion

We tested whether cerebral noradrenaline (NA) may play a central role in mediating the increased production of free fatty acids (FFAs) during cerebral ischemia. Levels of FFAs, cyclic AMP, and NA, as well as ATP, ADP, and AMP, were measured in cerebral cortex during decapitation ischemia in rats 2 weeks after unilateral locus ceruleus lesion. Comparisons were made between the results obtained from the contralateral cortex with normal NA content and the NA-depleted ipsilateral cortex. Although NA depletion was associated with a diminished transient rise of cyclic AMP in response to ischemia, it failed to influence the magnitude of FFA increase or the decline of energy state within the 15-min period of ischemia. A more than twofold increase of total FFAs (sum of palmitic, stearic, oleic, arachidonic, and docosahexaenoic acids) was observed in both hemispheres at 1 min after decapitation, when energy failure became manifest. The increased production of FFAs continued throughout the 15 min of ischemia, with a preferential rise in the levels of stearic and arachidonic acids. There was an inverse correlation between FFA levels and total adenylate pool. The results do not support a major role for NA and cyclic AMP in increasing cortical FFAs during complete ischemia. Instead, they are consistent with the view that impaired oxidative phosphorylation activates deacylating enzymes. Disturbance of reacylation due to energy depletion is probably another factor contributing to the continuous increase of FFAs during prolonged ischemia.

Fasciola hepatica: increase of glycogen phosphorylase activity due to prostaglandins

Both prostaglandin E1 (PGE1) and prostaglandin F2 alpha (PGF2 alpha) stimulate the glycogen phosphorylase (EC 2.4.1.1.) activity of Fasciola hepatica. Whole or sliced parasites were incubated with PGE1 (2.8 X 10(-7) and 2.8 X 10(-5) M) and PGF2 alpha (2.1 X 10(-7) and 2.1 X 10(-5) M) and enzyme activity was measured in homogenates prepared immediately following the incubation. No substantially different effect was noted between the two assayed doses of prostaglandins. Prostaglandins appeared to be less effective in sliced parasites.

The isolation of prostaglandin E from pig nasal mucosa

Prostaglandins of the E series (PGE) have been shown to be potent nasal vasoconstrictors but have not previously been isolated from the nasal mucosa. Here we report the isolation of a biologically active substance with properties similar to PGE from pig nasal mucosa. The substance was identified as PGE on the following criteria: 1 our isolation procedure demonstrated the presence of a biologically active polar acidic lipid; 2 caused contractions of the isolated rat stomach fundic strip similar to PGE2; 3 caused a prolonged nasal vasoconstriction similar to PGE2; 4 travelled on thin layer chromatogram with PGE. The PGE found in the nasal mucosa may have a role in the regulation of mucosal blood flow in normal and pathological conditions.

Relaxin inhibits prostacyclin release by the rat pregnant myometrium

Porcine relaxin (30 microgram/ml) when incubated with separated myometrial tissue from 20 day pregnant rats inhibited basal prostacyclin output by 50%. However, relaxin did not inhibit the increased prostacyclin output observed when myometrial tissue was incubated with the prostaglandin precursor, arachidonic acid (10 microgram/ml). When prostacyclin release was stimulated by incubation with oxytocin (10 mU/ml), however, relaxin completely inhibited the increased output. The results suggest that relaxin interferes with basal and oxytocin-stimulated prostacyclin formation in pregnant myometrial tissue by inhibiting the action of the enzyme phospholipase A2 which is responsible for liberating the precursor arachidonic acid endogenously.

Electrically induced tachyarrhythmia and the effect of propranolol on the release of cyclic AMP and prostaglandin E by the canine left ventricle

In anesthetized open-chest dogs, tachyarrhythmia (TA) was electrically induced by above-threshold stimuli via the right ventricle. During TA, a significant increase in the release of PGE and cAMP was observed in the canine coronary sinus blood (CSB). The efflux of cAMP corresponded with a concomitant increase in the left ventricular tissue level of this nucleotide. Pretreatment with propranolol (1.0 mg/kg i.v.) prevented the TA-induced changes in the level of PGE as well as cAMP in the CSB and in the tissue levels of cAMP. There was an increase in the activity of phosphorylase a in the myocardial tissue during TA which could be abolished by propranolol pretreatment. These results suggest possible interrelationships among catecholamines, cAMP, and PGE.

Influence of cardiac rhythm disturbances and antiarrhythmic drugs on the efflux of PGE, PGF2 alpha, cyclic AMP, and cyclic GMP in canine coronary sinus blood

In anaesthetized open-chest dogs, cardiac arrhythmias (CA) were induced by cumulative intravenous doses of aconitine or ouabain. Aconitine in a dose which did not induce CA had no influence on the PGE and PGF2 alpha effluxes into coronary sinus blood (CSB), whereas the PGE efflux into CSB increased after a subtoxic dose of ouabain. However, both PGE and PGF2 alpha effluxes were increased, when CA had developed. During aconitine induced CA, the PGE efflux was 6.5-fold and that of PGF2 alpha had increased by 80%. During ouabain induced CA, the effluxes of both PGs were about 3-fold. Propranolol and lidocaine decreased the PGF2 alpha efflux into CSB by about 50% and the PGE efflux was doubled after lidocaine and decreased after propranolol by about a third. The increased PGE efflux into CSB during CA was normalized after propranolol and quinidine if the CA was abolished or the cardiac rhythm improved. Lidocaine did not modify the increase in PGE efflux, despite the abolishment of CA. The increase in PGF2 alpha efflux was not influenced by antiarrhythmic drugs. The cyclic AMP and cyclic GMP in CSB remained unchanged during ouabain induced arrhythmias or after propranolol. The increased efflux of PGE into CSB during aconitine and ouabain induced CA and its abolishment by propranolol support the hypothesis that PGE participates in the modulation of increased sympathetic tone during CA.

Cyclic AMP and permeability coefficient of albumin of the isolated rat mesentery. Effects of Escherichia coli endotoxin

We have investigated the mechanisms whereby Escherichia coli endotoxin exerts its exudative effects, by using an isolated rat mesentery placed as a separation membrane between the two compartments of a diffusion cell. The permeability coefficient of albumin (PA) can be easily computed from the equilibration rate of 125I-labeled albumin added to one compartment. E. coli endotoxin increased PA in a concentration-related manner. Direct measurements revealed an early and transient increase in cyclic AMP and prostaglandin E-immunoreactive material. These effects of endotoxin could be inhibited by indomethacin. Calcium-depleted tissues have a low PA, even though cyclic AMP levels could still be increased by endotoxin. It incubations were prolonged beyond 90 min, PA remained elevated, but prostaglandin E and cyclic AMP levels fell to control values. Similar results were observed with trypsin-treated tissues. These results suggest that transmesenteric passage of albumin is increased in the presence of endotoxin. During the earlier part of the incubation (up to 90 min), the effects could be related to a local synthesis of prostaglandin E, and are controlled by cyclic AMP and intracellular calcium levels. During longer incubations (90-280 min) mesothelial exfoliation could occur, allowing free diffusion of albumin through the remaining interstitial tissue.

Free fatty acids in the rat brain in moderate and severe hypoxia

The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial PO2 35-40 mm Hg) or moderate (PO2 25-30 mm Hg) hypoxia. The effects of severe hypoxia (PO2 about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80-85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded tha hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.

Prostacyclin (PGI2) mediates hypoxic relaxation of bovine coronary arterial strips

Bovine coronary arterial strips (BCA) exhibiting spontaneous tone, relax in response to a decrease in the pO2 of the bathing medium. Experiments were performed to determine if prostaglandins (PGs) mediate the oxygen-induced changes in tension. BCA were equilibrated in Krebs-bicarbonate solution at 37 degrees C gassed with 95% O2, 5% CO2 and tension was measured isometrically. When the pO2 of the bathing medium was decreased, BCA exhibited reversible reductions in tension. Switching from 95% O2, 5% CO2 to 95% N2, 5% CO2 (anoxia) elicited an initial relaxation followed by a contraction. In contrast, a change to 5% O2, 5% CO2, 90% N2 (hypoxia) was followed by a sustained relaxation. Re-introduction of O2 to anoxic strips produced a biphasic response: relaxation followed by contraction. Indomethacin or eicosatetraynoic acid (EYA) increased tone and inhibited the relaxation produced by anoxia or hypoxia. Indomethacin or EYA did not inhibit the relaxation of anoxic strips during re-introduction of O2, but did inhibit the contraction partially. Relaxation of arterial strips to arachidonic acid (AA) was similar to relaxation to prostacyclin (PGI2). Anoxia limited the relaxation to AA but not to PGI2. We conclude that PG synthesis contributes to the basal tone and the hypoxia-induced relaxation of BCA. In addition, hypoxia, unless severe, does not prevent the conversion of AA to PGI2.

Influence of electrically induced tachyarrhythmia on the release of cyclic AMP and PGE in canine coronary sinus blood and on the level of cyclic AMP in myocardial tissue

In anaesthetized open-chest dogs tachyarrhythmia (TA) was electrically induced by above-threshold stimuli via the right ventricle. During TA a significant increase in the release of PGE and cyclic AMP of 20% and 40% of the control levels, respectively, was observed in the canine coronary sinus blood (CSB), whereas the level of PGF2 alpha remained nearly unchanged under these conditions. The efflux of cyclic AMP corresponded with a concomitant increase in the left ventricular tissue level of this nucleotide by 59% during TA. Pretreatment with the beta-adrenergic blocking agent propranolol (1.0 mg/kg i.v.) prevented the TA induced changes in the level of PGE as well as cyclic AMP in the CSB and in the tissue levels of cyclic AMP. Propranolol alone was without any effect on the efflux of cyclic AMP, but decreased significantly the efflux of PGE by 32%. There was an increase in the activity of phosphorylase a in the myocardial tissue from 10% to 20% of the total (a + b) activity of this enzyme during TA, which could be abolished by propranolol pretreatment. The results suggest possible interrelationships between catecholamines, cyclic AMP and PGE.

Antibody dependent cell-mediated cytotoxicity to herpes simplex virus in man: the influence of drugs on polymorphonuclear leucocyte and mononuclear effector cells

We have shown that the function of the effector cells in antibody mediated cell dependent cytotoxicity (ADCC) can be reduced by the use of a number of drugs and prostaglandins. Both polymorphonuclear leucocyte and mononuclear effector cells were studied. Aminophylline and isoproterenol markedly reduced this activity. All the prostaglandins tested--PGA1, A2, E1 and E2 had a similar but more profound effect. At a dose of 100 mg/ml hydrocortisone had relatively little influence and neither ASA nor indomethacin had any effect on the effector cells tested. It is suggested that the effect of PGE1 in stimulating a recrudescent herpes simplex infection may be by reducing the efficacy of ADCC in host defence.

Influence of the arachidonic acid cascade on the in vitro hepatic response to hypoxia

Studies were undertaken to determine the effect of arachidonic acid, the precursor of bisenoic prostanoic acid derivatives, on the response of the isolated, perfused rabbit liver to hypoxia. Two and one half hours of severe hypoxia resulted in significant increases in hepatic vascular perfusion pressure, tissue wet weight, and the rates of cellular loss of lactic dehydrogenase, malic dehydrogenase, and acid phosphatase into the perfusing medium. Hypoxia also increased the rate of hepatic PGF2 alpha production by 25% after 2 1/2 hours (p less than 0.05, hypoxia vs sham). The addition of arachidonic acid (0.1 microgram/g/min for 150 minutes) to the perfusion medium of hypoxic livers significantly attenuated the changes in perfusion pressure, tissue wet weight, and loss of cellular enzymes. Arachidonic acid administration increased the rate of PGF2 alpha production by 100% (p less than 0.05, sham vs hypoxia + arachidonic acid) within 30 min after hypoxia and maintained this rate for the duration of the study. These results demonstrate that hypoxia mediated prostaglandin F2 alpha synthesis in the rabbit liver can occur in the absence of neural and blood borne components and that significant activation of the arachidonic acid cascade via the administration of exogenous arachidonic acid has a salutary effect on hepatic hemodynamics and cellular integrity during hypoxia.

Oxygen requirement for prostaglandin biosynthesis

The formation of prostaglandins by vesicular gland cyclooxygenase can be regulated by O2 concentrations below 30 micron (20 mm Hg) with an apparent Km value of about 5 micron. This result suggests that most mammalian tissues might be expected normally to have sufficient O2 for some synthesis, and that only occasionally, would the level of oxygen available within some tissues become marginally inadequate to sustain a high rate of prostaglandin biosynthesis.

Antagonism by indomethacin of neurogenic hyperthermia produced by unilateral puncture of the anterior hypothalamic/preoptic region

1. In unanaesthetized rats, restrained at an ambient temperature of 24 degrees C, the anterior hypothalamic/preoptic (AH/PO) region was lesioned unilaterally by acute mechanical puncture.2. In control (no pre-treatment) rats, unilateral AH/PO puncture produced a neurogenic hyperthermia which began immediately, reached its peak magnitude (mean peak magnitude = +2.3 degrees C) within 60-90 min and persisted usually for 8-16 hr. At defervescence, core temperature fell to a level near that of the pre-lesioning base line.3. The prostaglandin synthesis inhibitor, indomethacin, administered I.P. at doses of 5 and 15 mg/kg 1 hr before puncture of the AH/PO region, attenuated the lesion-induced hyperthermia in a dose dependent fashion. The higher dose reduced peak magnitude by 80% and the 6 hr Fever Index by 88%. The vehicle used to dissolve the indomethacin (60% DMSO/40% saline) did not significantly attenuate the hyperthermia.4. In rats that were hyperthermic after AH/PO damage, indomethacin (10-15 mg/kg I.P.) caused core temperature to fall promptly to near the prelesion base line. Reversal occurred whether the indomethacin was injected while core temperature was still rising or late in the plateau phase of the hyperthermia.5. It is suggested that the neurogenic hyperthermia elicited by unilateral lesioning of the AH/PO region was mediated by prostaglandins released from injured tissue and possibly from extravasated blood. Evidence is cited indicating that the most likely sites of action of the released prostaglandins are the surviving portion of the AH/PO region on the punctured side and the intact contralateral AH/PO region.

Effect of fasting and streptozotocin-diabetes on the coronary flow in isolated rat hearts: A possible role of endogenous catecholamines and prostaglandins

The coronary flow rate of retrogradely perfused hearts from fasted (group I) and streptozotocin-diabetic rats (group II) is increased when compared with the flow rate of control, fed animals (group III). The enhanced coronary flow is absent when hearts of groups I and II are perfused in the presence of indomethacin (1 microgram/ml) in the perfusion fluid and the lowest flow rates are observed after depletion of the endogenous catecholamines by reserpin. Hearts from groups I and II showed a marked increase in prostaglandin-release which was counteracted both in the presence of indomethacin (1 microgram/ml) and by reserpin-pretreatment. The results suggest that the increased coronary flow rates in hearts from fasted and streptozotocin-diabetic rats are mediated by an effect of released endogenous catecholamines on coronary vascular smooth muscle and by a catecholamine-induced release of vasodilatory, prostaglandin-like substances.

Aspirin-induced depression of renal function

We observed elevation of serum creatinine and blood urea nitrogen and decrease in creatine clearance in patients taking anti-inflammatory doses of aspirin. In 13 of 23 patients with systemic lupus erythematosus increases in serum creatinine ranged from 27 to 163 per cent, and those in urea nitrogen from 42 to 270 per cent. Sequential creatinine-clearance studies, available in 11 of the 13 patients, demonstrated decreases up to 58 per cent. Patients with aspirin-induced changes in renal function were more likely to have active renal disease (P =0.035) or hypocomplementemia (P =0.030). Four of 22 patients with rheumatoid arthritis and two of three normal volunteers also demonstrated biochemical changes. The rate of aspirin-induced alterations was significantly higher in systemic lupus erythematosus (P =0.007) than in rheumatoid arthritis. Aspirin, and other nonsteroidal anti-inflammatory agents, can have a major reversible effect on renal function that may influence the interpretation of clinical data.