Effects of experimental diabetes on spontaneous contractions, on the output of prostaglandins and on the metabolism of labelled arachidonic acid, in uteri isolated from ovariectomized rats. Influences of estradiol

Spontaneous changes in isometric developed tension (IDT) as a function of time after isolation (contractile constancy) in uteri from control-castrated and castrated chronic streptozotocin-diabetic rats, were explored. The effects of injecting 17-beta estradiol (Eo) were also studied. No differences in the minor changes of contractile constancy, between control and diabetic preparations, during a period of 60 min, were detected, whereas uteri from non-diabetic Eo injected animals (0.5 + 1.0 ug, prior to sacrifice), exhibited a profound reduction of IDT, significantly greater than in tissues obtained from Eo injected-diabetic rats. Moreover, basal generation and outputs into the suspending solution of prostaglandins (PGs) E1, E2 and F2 alpha, were explored in the same groups, at 60 min following tissue isolation. The basal outputs of these three PGs were similar in castrated control rats, but preparations from castrated-diabetics released significantly more PGE1. The administration of Eo to castrated-diabetics, failed to alter the releases of the three PGs explored. In addition, the metabolism of labelled arachidonic acid (AA) into different prostanoids (6-keto-PGF1, PGF2, PGE2 and thromboxane B2-TXB2), was also investigated. The non-diabetic spayed rat uterus converted AA into these four prostanoids, the transformation into 6-keto-PGF1 alpha (as an index of PGI2 formation) being the most prominent. In preparations from diabetic rats the formation) being the most prominent. In preparations from diabetic rats the formation of 6-keto-PGF1 alpha, PGF2 alpha and PGE2, was significantly smaller than in controls, whereas a greater % of TXB2 formation (as an index of TXA2), was detected. On the other hand uterine preparations from non-diabetic spayed rats injected with Eo formed less 6-keto-PGF1 alpha and PGE2 and similar amounts of PGF2 alpha or of TXB2 from AA, than Eo injected controls, whereas uteri from castrated diabetic animals injected with Eo, formed a similar % of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 from AA, than tissue preparations from non-estrogenized controls. However, the enhanced transformation of the labelled fatty acid precursor (AA) into TXB2 in the diabetic group, was significantly reduced by the steroid. The role of the augmented generation and release of PGE1 in uteri from diabetic rats is discussed in terms of precedents indicating the relevance of PGs type E supporting rat uterine motility. In addition the influence of Eo is attractive, because its reducing effect on TX production, in diabetes, a disease known to be accompanied by enhanced synthesis of vasoconstrictor and platelet aggregation TXA2, and by frequent obstructive circulat     

Effect of dipyridamole on prostanoid production in rat isolated atria.

The effect of 0.01 microM dipyridamole on prostanoid production was studied in atria from normal, acute diabetic and insulin-treated diabetic rats. Diabetes was induced by i.v. administration of 65 mg/kg of streptozotocin (STZ) and the rats were killed 5 days later. Atria were incubated during 60 min in Krebs solution. The prostanoids 6-keto-prostaglandin (PG) F1alpha (6-keto-PGF1alpha) and thromboxane (TX) B2, stable metabolites of prostacyclin and TXA2, respectively, as well as PGE2 were measured by reversed phase high-performance liquid chromatography-UV. In diabetic atria, 6-keto-PGF1alpha production was reduced by 50% whereas TXB2 release was increased two-fold compared to the controls, with a significant decrease in the 6-keto-PGF1alpha/TXB2 ratio. The preincubation with 0.01 microM dipyridamole for 30 min increased 6-keto-PGF1alpha production in control, diabetic and insulin-treated diabetic atria whereas TXB2 release was not modified. This effects provoked an significant increase in the 6-keto-PGF1alpha/TXB2 ratio. In conclusion, STZ diabetes reduces the 6-keto-PGF1alpha/TXB2 ratio impairing the functional status of the atria. Dipyridamole increased this ratio in atria from diabetic and insulin-treated diabetic rats, thus opposing the effects of STZ diabetes. This fact suggests the possibility of a participation of the drug in pathologies characterized by an imbalance in the production of vasodilator and vasoconstrictor prostanoids.     

Involvement of inducible isoforms of COX and NOS in streptozotocin-pancreatic damage in the rat: interactions between nitridergic and prostanoid pathway

Streptozotocin-induced pancreatic damage involves nitric oxide (NO) and prostaglandins (PGs) overproduction. In this work we aim to evaluate a putative relationship between the elevated NO levels and the altered prostanoid production in pancreatic tissue from streptozotocin-diabetic rats. Total NOS activity and nitrate/nitrite pancreatic levels in tissues from diabetic rats are decreased when the cyclooxygenase (COX) inhibitor indomethacin (INDO) is added to the incubating medium, while the addition of PGE(2)increases nitrate/nitrite production and NOS levels. INDO and PGE(2)selectively affect Ca(2+)-dependent NOS (iNOS) activity in diabetic tissues, and they have not been able to modify nitrate/nitrite levels, iNOS or Ca(2+)-dependent (cNOS) in control tissues. When the NOS inhibitor L-NMMA was present in the incubating medium, control pancreatic [(14)C]-Arachidonic Acid ([(14)C]-AA) conversion to 6-keto PGF(1 alpha)and to TXB(2)was lower, and PGF(2 alpha), PGE(2)and TXB(2)production from diabetic tissues diminished. The NO donors, spermine nonoate (SN) and SIN-1, enhanced TXB(2)levels in control tissues, while PGF(2 alpha), PGE(2)and TXB(2)levels from diabetic tissues were increased. PGE(2)production from control and diabetic tissues was assessed in the presence of the NO donor SN plus INDO or NS398, a specific PG synthase 2 inhibitor. When SN combined with INDO or NS398 was added, the increment of PGE(2)production was abolished by both inhibitors in equal amounts, indicating that the activating effect of nitric oxide is exerted on the inducible isoform of cyclooxygenase. In the diabetic rat, prostaglandins and NO seem to stimulate the generation of each other, suggesting a lack of regulatory mechanisms that control the levels of vasoactive substances in acute phase of beta-cell destruction.     

Comparison of plasma prostanoid levels in the human cord artery in normal and fetal distressed deliveries

Prostaglandin E2 (PGE2), thromboxane B2 (TXB2; as a stable metabolite of TXA2), prostaglandin F2 alpha (PGF2 alpha) and 6-keto-PGF1 alpha (as a stable end product of prostacyclin) have been measured by using specific radioimmunoassay in the plasma of the cord artery immediately after delivery before the cord was clamped. Plasma prostanoid concentrations in normal deliveries (n = 8, as controls) were 24.8 +/- 2.6 (PGE2), 246.8 +/- 37.0 (TXB2), 122.2 +/- 13.3 (PGF2 alpha) and 82.1 +/- 7.7 (6-keto-PGF1 alpha) respectively (pg/ml, mean +/- s.e). On the other hand, in fetal distressed deliveries showing continuous bradycardia (n = 6), they increased significantly to 275.4 +/- 20.1 (PGE2), 948.6 +/- 102.5 (TXB2), 218.0 +/- 21.4 (PGF2 alpha) and 1498.6 +/- 298.4 (6-keto-PGF1 alpha) respectively (pg/ml, mean +/- s.e, p less than 0.005). However, both PGF2 alpha/PGE2 and TXB2/6-keto-PGF1 alpha ratios declined significantly from 4.70 +/- 0.33 to 0.68 +/- 0.05 and from 3.07 +/- 0.37 to 0.68 +/- 0.12 respectively (mean +/- s.e, p less than 0.005) in the fetal distressed group compared with those of the controls. From these results, it may be concluded that the cord artery, which is known as the patent source for the production of PGE2 and prostacyclin, did exert a sufficiently strong reaction to overcome the undesirable haemodynamic changes to maintain the fetal well-being in utero.     

Prostaglandin E production by uteri of ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn.

Antiprogesterone steroid, ZK98299 (Schering, Germany) or RU38486 (Roussel Uclaf, France), has been administered to ovariectomized early pregnant rats receiving continuous steroid replacement. At 24 h later, uterine explants of rats treated with ZK98299 produced significantly greater amounts of prostaglandin E (PGE) than did controls or animals treated with RU38486. The PGE/PGF2 alpha production ratio for uteri of rats treated with ZK98299 or RU38486 was markedly lowered compared to controls, and a significant decrease occurred in the PGE/6-keto PGF1 alpha production ratio for rats treated with RU38486. For ovariectomized early pregnant rats in which progesterone has been withdrawn, a significant reduction in uterine PGE production occurred when compared to control animals. There was also a marked decrease in PGE/PGF2 alpha production ratio, and the PGE/6-keto PGF1 alpha production ratio tended to be lowered relative to controls. The stimulated production (as by ZK98299) or unchanged production of PGE (as by RU38486) indicates a selective action on uterine PGE synthesis among the antiprogesterone steroids, and these findings cannot be explained simply in terms of a blockage of progesterone receptors.     

Calcium-dependent prostaglandin biosynthesis by lipopolysaccharide-stimulated rat Kupffer cells.

Isolated rat Kupffer cells produced and released prostaglandin (PG) E2, 6-keto-PGF1 alpha, and thromboxane B2 (TXB2) in response to lipopolysaccharide (LPS) stimulation. This elevation of PGE2, 6-keto-PGF1 alpha and TXB2 in the medium was not observed when cells were cultured in the absence of extracellular calcium or in the presence of an extracellular calcium chelator, EGTA. An intracellular calcium antagonist, TMB-8, also suppressed the production of PGE2, 6-keto-PGF1 alpha and TXB2 in a concentration-dependent manner. The intra-cellular calcium concentration of Kupffer cells elevated early after the addition of LPS determined by the use of fura-2 and a fluorescence microscopy. Moreover, calmodulin inhibitors, W-7 and W-13, apparently inhibited the production of PGF2, 6-keto-PGF1 alpha and TXB2. All these results suggest that LPS-induced PG production by stimulated rat Kupffer cells may be regulated by a calcium-calmodulin pathway.     

Effects of nitrogen dioxide exposure on the contents of prostaglandins and thromboxane B2 in broncho alveolar lavage

Effects of 10 ppm nitrogen dioxide (NO2) exposure on the contents of prostaglandins (PGs) and thromboxane (TX) B2 in bronchoalveolar lavage (BAL) of rats were studied. In the BAL of normal rats, the amounts of PGs and TXB2 in the whole lavage were 6-keto-PGF1 alpha (38.0 +/- 6.4 ng) greater than TXB2 (11.8 +/- 4.0 ng) greater than PGF2 alpha (5.7 +/- 1.6 ng) much greater than PGE (0.5 +/- 0.3 ng). Rats were exposed to NO2 for 1,3,5,7 and 14 days. The NO2 exposure decreased in the level of 6-keto-PGF1 alpha by about 35% throughout the exposure. The level of TXB2 was higher in the day 5 exposure group (155%). The contents of PGF2 alpha and PGE first, decreased and then transiently increased on days 3 and 5. PG 15-hydroxy-dehydrogenase activity of lung homogenate decreased correspondingly on day 3 and 5. Then the contents PGF2 alpha and PGE decreased on day 7 and 14. 6-keto-PGF1 alpha and TXB2 are stable metabolites of PGI2, a strong bronchorelaxant and TXA2, a strong bronchoconstrictor respectively. Therefore the results suggested that the decrease in 6-keto-PGF1 alpha, a major prostanoid in the BAL and the increase in TXB2 may correlate with broncho constriction by NO2 exposure.     

Altered myocardial prostaglandin synthesis in spontaneously diabetic rats

Patients with diabetes mellitus have an increased susceptibility to heart disease. The exact mechanism for this phenomenon is unclear. Abnormalities in prostaglandin (PG) production have been suggested as a possible cause. In this connection, we examined the PG synthetic capacity of cardiac microsomes from spontaneously diabetic rats. Cardiac microsomes from diabetic and control rats produced varying amounts of 6-keto-PGF1 alpha (stable degradation product of PGI2), PGE2, PGD2, PGF2 alpha, and TXB2 (stable breakdown product of TXA2). In both instances the production of 6-keto-PGF1 alpha predominated, however, microsomes from diabetic rats showed markedly greater conversion of arachidonic acid to all the PG products, especially 6-keto-PGF1 alpha. When PGF2 alpha metabolism was detected between diabetic and control heart preparations. These results show an enhanced cyclooxygenase activity in diabetic rat hearts without any change in prostaglandin dehydrogenase activity. Such a change may promote some of the cardiac alterations seen in diabetic mellitus.     

Uterine production of prostaglandins F2 alpha and 6-keto-F1 alpha by ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn.

Ovariectomized early pregnant rats given continuous steroid replacement therapy have been treated with antiprogesterone steroid, ZK98299 or RU38486. At 24 h following treatment, uterine explants in culture were found to produce significantly greater amounts of PGF2 alpha, but not of 6-keto-PGF1 alpha, when compared to controls. ZK98299 and RU38486 gave almost identical levels of uterine PG production. The 6-keto-PGF1 alpha/PGF2 alpha production ratio for uteri of treated rats was decreased by 45% relative to controls. Similar changes in uterine PGF2 alpha production and 6-keto-PGF1 alpha/PGF2 alpha ratio have been shown for ovariectomized early pregnant rats in which progesterone has been withdrawn when compared to control animals. It has been suggested that inhibiting or withdrawing progesterone in rat uteri exposed to estradiol and progesterone may lead to a stimulation of endoperoxide F-reductase and/or E2 9-ketoreductase activities. The presence of luminal fluid in the uteri was observed for animals treated with antiprogesterone steroid or in which progesterone had been withdrawn. This was associated with a decrease in % dry weight for the uteri of these animals.     

Effect of prostaglandins against alloxan-induced diabetes mellitus

Previously, we observed that alloxan-induced in vitro cytotoxicity and apoptosis in an insulin secreting rat insulinoma, RIN, cells was prevented by prior exposure to prostaglandin (PG) E(1), PGE(2), PGI(2), PGF(1)(alpha), and PGF(3)(alpha) (P<0.05 compared to alloxan), whereas thromboxane B(2) (TXB(2)) and 6-keto-PGF(1)(alpha) were ineffective. In an extension of these studies, we now report that prior intraperitoneal administration of PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) prevented alloxan-induced diabetes mellitus in male Wistar rats, whereas PGI(2), TXB(2), and 6-keto PGF(1)(alpha) were not that effective. PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) not only attenuated chemical-induced diabetes mellitus but also restored the antioxidant status to normal range in red blood cells and pancreas. These results suggest that PGE(1), PGE(2), PGF(1)(alpha), and PGF(3)(alpha) can abrogate chemically induced diabetes mellitus in experimental animals and attenuate the oxidant stress that occurs in diabetes mellitus.     

Effects of prostaglandins and of leukotriene C4 on the metabolism of labelled glucose in uteri isolated from ovariectomized-diabetic rats. Influences of 17-beta-estradiol and of insulin.

The influences of exogenous PGE1, PGE2, PGF2 alpha, LTC4 and insulin (INS) on glucose oxidation in uterine strips isolated from ovariectomized-diabetic (OVD) and ovariectomized-estrogenized-diabetic (OVED) rats, were studied. The spayed animals were made diabetic by a single injection of streptozotocin (65 mg.kg-1 body weight). The effects of prostaglandins were studied in the presence of indomethacin (INDO) in the incubation medium and the effects of LTC4 in the presence of INDO and nordihydroguaretic acid (NDGA). These procedures were followed in order to avoid the possible influences of endogenous derivatives of arachidonic acid formed by the activity of cyclooxygenase and of lipoxygenases. INDO and NDGA did not modify significantly the formation of 14CO2 from U-14C-glucose in uteri from OVD and from OVED rats. INS (0.5 U.ml-1) augmented significantly labelled glucose metabolism, both in OVD as well as in OVED rats. On the other hand, added PGE1, PGE2, PGF2 alpha or LTC4 failed to alter glucose metabolism in uteri from OVD rats. Only PGE1 was able to increase significantly (p less than 0.05) 14CO2 production from labelled glucose in uterine strips from OVED rats. In OVD rats the stimulatory action of INS on uterine glucose metabolism was significantly enhanced by exogenous PGE1, but not modified by PGE2, by PGF2 alpha or by LTC4. PGE1, PGE2 and LTC4 sensitized uterine strips obtained from OVED rats to the effects of INS. The possible importance of PGE1 in improving uterine glucose metabolism in diabetic animals is discussed.     

The biosynthesis of the 3-series prostaglandins in rat uterus after alpha-linolenic acid feeding: Mass spectroscopy of prostaglandins E and F produced by rat uteri in tissue culture

The abnormal uterine activity associated with dietary n-3 fatty acids may result from competitive inhibition of PG2 production. Uterine synthesis of 2- and 3-series prostaglandins F(PGF) and E(PGE) was studied using mass spectrophotometry in rats fed diets containing predominantly n-3 fatty acid, n-6 fatty acid, or control pelleted diet. Mass spectra of PGF (Me, TMS and Me, TBDMS derivatives) synthesised by uteri of n-3 fed rats were characterised by 8 ions containing the n-3 double bond, and m.i.d. of the 651/653 ions of PGF-Me, TBDMS indicated PGF3 alpha synthesis (44 +/- 8% and 13 +/- 2% of PGF release by uteri incubated + or -5 micrograms/ul calcium ionophore A23187 respectively). In uteri from the control diet group incubated with ionophore, PGF3 alpha ions were detected and PGF 3 alpha represented 9.5 +/- 1.0% of PGF alpha release. Similarly, analysis of PGE from uteri of n-3 fed rats indicated that PGE3 (16 +/- 6% of PGE) was released in the presence of ionophore A23187. Synthesis of 3-series PG by rat uteri was detected after only 3 weeks of n-3 diet. The capacity to synthesise 3-series PG increased at intracellular calcium concentrations which mimicked cell calcium during decidual autolysis at parturition. These experiments suggest that uterine synthesis of 3-series PG is regulated by the specifity of enzymes incorporating fatty acids, rather than by the cyclooxygenase enzyme.     

Prostanoid synthesis by vascular slices and cultured vascular cells of piglet aorta

Biosynthesis of prostanoids was studies in vascular slices of human umbilical arteries, piglet aorta and vena cava as well as in cultured vascular cells of piglet aorta. After preincubation with radioactive labeled arachidonic acid, prostanoids in the incubation media of slices or cultured cells were measured by radioimmunoassay or by radioactivity determination of labeled compounds following separation on reserved-phase high performance liquid chromatography. In all vascular slices 6-keto-PGF1α was the main prostanoid found, followed by PGE2. Thromboxane B2 and PGF2α were also formed, but only in trace amounts. In cultured cells taken from the three layers of the vascular wall, the prostanoid profiles differed markedly from those obtained from vascular slices. Each cell strain showed a specific prostanoid pattern. Endothelial cells synthesized predominantly 6-keto-PGF1α and PGF2α. In smooth muscle cells no 6-keto-PGF1α could be detected; here the predominant prostanoid was PGE2. PGF2α was formed in smaller quantities. Fibroblasts synthesized all prostanoids (PGE2, PGF2α, TXB2, 6-keto-PGF1α), PGE2 and PGF2α being the major products. In vascular slices and in cultured endothelial cells, the predominant prostacyclin derivative detected was 6-keto-PGF1α; the enzymatic PGI2-metabolite, 6,15-diketo-PGF1α, could be detected only in piglet vena cava slices in small amounts.     

Prostaglandin production by phagocytic cells of the mouse thymic reticulum in culture and its modulation by indomethacin and corticosteroids

The production of prostaglandins by phagocytic cells of the thymic reticulum in culture (P-TR) was studied by using high pressure liquid chromatography and radioimmunoassay. Radioimmunologic determinations showed that thromboxane B2 (TXB2), prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1 alpha (6 keto-PGF1 alpha) were the major compounds released into the culture medium, whereas prostaglandin F2 alpha (PGF2 alpha) was only a minor component. Indomethacin and dexamethasone exerted a similar pattern of differential inhibition of the secretion of prostanoids. PGE2 and 6-keto PGF1 alpha productions were markedly decreased by these anti-inflammatory drugs, whereas those of TXB2 and PGF2 alpha were not or were only slightly affected. Experiments performed with an antiglucocorticoid compound (RU 38486) showed that the steroid-induced inhibition of prostanoid secretion is a classical receptor-mediated action. These results demonstrated that phagocytic cells of the thymic reticulum, which resemble the thymic interdigitating cells, produce several types of prostaglandins. Because it has been described that P-TR regulate thymocyte proliferation in vitro via the secretion of both interleukin 1 and PGE2, these results suggest that anti-inflammatory agents may be able to modulate the thymic microenvironment and, consequently, thymocyte proliferation.     

Thromboxane B2, 6-keto-prostaglandin F1 alpha, and prostaglandin F2 alpha production by contracting pregnant rate uteri in vitro

While prostaglandin production by uterine tissue has been shown to be involved in the contractile mechanism of this tissue, less attention has focused upon the involvement of other prostanoids. We have simultaneously measured in vitro isometric contractility of pregnant rat uteri with the release of prostaglandin F2 alpha (PGF), 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) and thromboxane B2 (TXB2) into the bathing medium under various conditions. Frequency of uterine contractions and integrated contractile force (ICF) increased from 15 days of gestation and peaked at the time of parturition. Activity was generally greatest during the first 15 min of incubation except during parturition and on Day 1 postpartum when the uterine segment remained active for 1 h experimental period. Indomethacin (INDO) significantly reduced contractile activity regardless of gestational stage. PGF, TXB2, and 6-k-PGF1 alpha increased with gestational age, peaking at the time of parturition. Production was greatest during the first 15 min of incubation and INDO inhibited production of each prostanoid regardless of gestational stage. Imidazole (100 micrograms/ml) inhibited TXB2 production without affecting PGF or 6-k-PGF1 alpha levels. Frequency of contraction and ICF were not affected by imidazole treatment despite TXB2 reduction. These data demonstrate that the in vitro uterus from pregnant rats is capable of producing prostanoids other than prostaglandins and their production generally parallels uterine contractile activity. Thus, the possibility that these prostanoids are involved in physiologic changes during parturition warrants further investigation.     

Influence of interleukin-1alpha and COX-2 over the metabolism of arachidonic acid and glucose in isolated uterus of restricted diet rats

Isolated uteri from rats fed with a normal diet convert [14C]arachidonate into eicosanoids: PGE(2), PGF(2alpha), TXB(2) and 6-keto-F(1alpha). Restricted diet (50% of the normal diet, during 25 days) diminishes the levels of PGE(2), PGF(2alpha) and TXB(2). The addition of Interleukin-1alpha to the Krebs-Ringer bicarbonate medium increases sharply the production of eicosanoids. Inhibitors of nitric oxide synthase, Nomega-nitro-L-arginine methyl ester or aminoguanidine, do not prevent eicosanoids increase. Conversely, NS-398 (a selective inhibitor of COX-2) blocks the increase of eicosanoids while PGE(2) blocks eicosanoids production mediated by IL-1alpha. Other experiments with uteri of underfed rats confirm that interleukin-1alpha produces an increase in the glucose metabolism. The addition of Nomega-nitro-L-arginine methyl ester, aminoguadinine or NS-398 blocked such stimulation. It is concluded that Interleukin-1alpha produces an increase of glucose metabolism in uteri isolated from underfed rats by two different mechanisms, both involving COX-2: (1) nitric oxide independent and (2) nitric oxide dependent.     

Altered prostanoid formation in human umbilical vasculature in response to variations in oxygen tension

Prostanoid formation in human umbilical vessels perfused in vitro was assessed at different oxygen tensions. At an atmosphere of 5% oxygen the production rate of prostacyclin (measured as 6-keto-PGF1 alpha) was higher, while those of thromboxane A2 (measured as TXB2), PGE2 and PGF2 alpha were lower than with 20%, 50% and 95% oxygen. The stimulatory effect of angiotensin II on prostanoid production was found to be independent on the prevailing oxygen tension. Vascular formation of prostanoids thus seems to be at least partially affected by the ambient oxygen tension. Though altered oxygen tension does not seem to affect angiotensin induced prostanoid formation, the action of other vasoactive agents influencing vascular formation of prostanoids may respond differently to hypoxia or hyperoxia.     

Prostacyclin induces a surprising long-lasting motility in quiescent uterine strips (indomethacin-treated) isolated from ovariectomized rats

Dose-response curves for several prostaglandins (PGI2; PGD2; PGF2 and PGE2); BaCl2 or prostaglandin metabolites (15-keto-PGF2 alpha; 13,14-diOH-15-keto-PGF2 alpha; 6-keto-PGF1 alpha and 6-keto PGE1 in quiescent (indomethacin-treated) uterine strips from ovariectomized rats, were constructed. All PGs tested as well as BaCl2, triggered at different concentrations, evident phasic contractions. Within the range of concentrations tested the portion of the curves for the metabolites of PGF2 alpha was shifted to the right of that for PGF2 alpha itself; the curve for 6-keto-PGF1 alpha was displaced to the right of the curve for PGI2 and that for 6-keto-PGE1 to the left. It was also demonstrated that the uterine motility elicited by 10(-5) M PGF2 alpha and its metabolites was long lasting (more than 3 hours) and so it was the activity evoked by PGI2;6-keto-PGF1 alpha and BaCl2, but not the contractions following 6-keto-PGE1, which disappeared much earlier. The contractile tension after PGF2 alpha; 15-keto-PGF2 alpha; 13,14-diOH-15-keto-PGF2 alpha and PGI2, increased as time progressed whilst that evoked by 6-keto-PGF1 alpha or BaCl2 fluctuated during the same period around more constant levels. The surprising sustained and gradually increasing contractile activity after a single dose of an unstable prostaglandin such as PGI2, on the isolated rat uterus rendered quiescent by indomethacin, is discussed in terms of an effect associated to its transformation into more stable metabolites (6-keto-PGF1 alpha, or another not tested) or as a consequence of a factor which might protects prostacyclin from inactivation.     

Plasma prostaglandin levels and circulating fuel levels in rats with diabetic ketoacidosis: effects of cyclooxygenase inhibitors and of alpha and beta adrenergic blockade

We studied the effects of two structurally unrelated inhibitors of the fatty acid cyclooxygenase and of alpha and beta adrenergic blockade on the elevated plasma levels of 13,14-dihydro-15-keto-prostaglandin (PG)E2, 6-keto-PGF1 alpha and thromboxane (TX)B2, the stable derivatives of PGE2, PGI2 (prostacyclin) and TXA2, respectively, in rats with streptozotocin-induced diabetic ketoacidosis (DKA). Meclofenamic acid and indomethacin each produced a significant decrease in the elevated plasma levels of 13,14-dihydro-15-keto-PGE2, 6-keto-PGF1 alpha and TXB2. Phentolamine significantly reduced the plasma level of TXB2 but had no effect on the elevated circulating levels of glucose, free fatty acids, total ketones, 13,14-dihydro-15-keto-PGE2 or 6-keto-PGF1 alpha. Propranolol significantly reduced the elevated circulating levels of glucose, free fatty acids and total ketones but had no effect on the levels of the three prostaglandin derivatives. The ability of meclofenamic acid and indomethacin to reduce the plasma levels of 13,14-dihydro-15-keto-PGE2, 6-keto-PGF1 alpha and TXB2 confirms that the plasma levels of these three derivatives are elevated in rats with DKA. Since abnormalities in the production of PGI2 and perhaps other cyclooxygenase derivatives may contribute to the pathogenesis of certain important hemodynamic and gastrointestinal features of DKA, cyclooxygenase inhibitors may play a role in the management of selected patients with this disorder. Alpha adrenergic activity is essential for the maintenance of the elevated plasma TXB2 level in rats with DKA. The fall in the plasma TXB2 level during alpha adrenergic blockade appears to reflect inhibition of platelet aggregation and platelet TXA2 production, but other sources of the elevated plasma TXB2 level in DKA are not excluded. Beta adrenergic activity contributes to the maintenance of elevated circulating levels of glucose, free fatty acids and total ketones in experimental DKA but not to the elevated plasma levels of the prostaglandin derivatives.     

Prostaglandin release by normal and osteomyelitic human bones

The release of prostaglandin E (PGE) and prostacyclin (as 6-keto PGF1 alpha) by human osteomyelitic bone, compared with normal (control) bone, incubated in vitro was evaluated. Prostacyclin was the main arachidonic acid metabolite released by normal human bone, and similar quantities were released by osteomyelitic bone. However, PGE production was 5-30-fold higher in osteomyelitic bone, compared with control, thus becoming the major prostanoid in this disease. It is concluded that PGE production is probably involved in the inflammatory and/or bone resorption processes that occur in osteomyelitis.