Prostaglandins, leukotrienes, and essential fatty acids最新文献

To elucidate the precise mechanisms of airway hyperresponsiveness induced by prostaglandin F2 alpha (PGF2 alpha) and thromboxane A2 (TXA2), we investigated the effects of the subthreshold dose (the highest dose which does not lead to contraction) of PGF2 alpha and stable TXA2 analogue, STA2 (epithiomethano-TXA2), on the smooth muscle contraction evoked by acetylcholine (ACh) and electrical field stimulation (EFS) in the canine trachea. These prostanoids produced no changes in the contractile response to both these stimuli. Thus, neither PGF2 alpha nor TXA2 affect the smooth muscle, as the site of action for ACh is the muscarinic receptor located on smooth muscle. Neither compound affect the postganglionic vagal efferent nerve, because the EFS contracts smooth muscle via activation of the postganglionic vagal efferent neuron. This study, together with our previous observation, suggests that PGF2 alpha and TXA2 induce airway hyperresponsiveness by stimulating vagal sensory endings and by activating the reflex pathway.

In macrophages, isolated from the peritoneal fluid of rats, after activation, formation of metabolites of arachidonic acid occurs both by the cyclooxygenase and lipoxygenase pathways. The cells of normal animals produce mainly cyclooxygenase products. After adrenalectomy, a considerable increase occurs in the formation of lipoxygenase products, and less in those of the cyclooxygenase (1). In the experiments described here, the effect of adrenalectomy on the presence of leukotriene B4 (LTB4), 6-keto-PGF1 alpha and thromboxane B2 (TxB2) in the peritoneal fluid is determined.

The effect of estradiol administration on renal prostaglandin (PG) E2 biosynthetic activity in rats was studied. A specific radioimmunoassay for PGE2 was developed and applied in the quantitation of PGE2 biosynthesis in kidney. Conversion of exogenous arachidonic acid into PGE2 by renal microsomal fraction was assayed. Formation of PGE2 was linear in fashion up to 5 min incubation at 37 degrees C, and linear in fashion up to 3.5 mg of microsome used as enzyme source. The renal biosynthesis of PGE2 was significantly increased by estradiol treatment.

Misoprostol, a prostaglandin (PG) E1 analogue, is one of the most effective radiation protectors of the PGs investigated to date. Misoprostol-induced protection is also additive to protection by the widely studied thiol compound, WR-2721. The mechanism of PG-induced radiation protection and its interaction with WR-2721 is unknown. One important step in the investigation of the mechanism is to determine if PG-induced protection and its interaction with WR-2721 is mediated through PG receptor sites. A direct determination of receptor sites on murine intestinal clonogenic cells could not be made; however an indirect approach was possible. Misoprostol is composed of four stereoisomers of about equal proportions of which only one is gastric antisecretory and cytoprotective. Studies reported here compared radiation protection by this active isomer with that of one of the three inactive isomers. Furthermore, the additional protection of the two isomers when administered with WR-2721 was investigated. Results showed that only the active isomer was protective from radiation injury and this isomer was the only one which afforded additional protection with WR-2721. These data show that PG-induced radiation protection is receptor site dependent and stereospecific.

This study assessed the hemodynamic and permeability effects of exogenous, synthetic leukotriene B4 (LTB4) on normal rat lungs and lungs from rats preexposed to oxygen for 48 h, which were isolated and perfused at constant flow in vitro. Adult, Sprague-Dawley rats were exposed to air or greater than 97% O2 for 48 h. After exposure, their lungs were removed from the thorax, ventilated with normoxic gas, and perfused at 12 ml/min with Krebs-Ringer bicarbonate buffer which contained 5 mM glucose and 3 mg/ml albumin. A total of 5.55 micrograms of synthetic LTB4 was infused in three separate boluses over 15 minutes. Perfusion and airway pressures were monitored, and the lungs release of 6-ketoprostaglandin F1 alpha and thromboxane B2 (TXB2) into the effluent from the pulmonary vasculature was measured by radioimmunoassay. The LTB4 had no measureable effects on pulmonary vascular pressures. LTB4 infusion caused a pronounced increase in permeability, indicated by increased albumin concentrations in alveolar lavage fluid from O2-preexposed lungs. Release of TXB2 from both air- and O2-preexposed lungs was increased after LTB4 infusion, while the change in 6-ketoprostaglandin F1 alpha release was not statistically significant. Both the increase in permeability enhanced TXB2 released after LTB4 infusion were inhibited by 10 microM indomethacin in the perfusate. These data indicate that exogenous LTB4 increases microvascular permeability in O2-exposed lungs in association with increased release of TXB2 into the pulmonary vascular effluent.

Leukotriene (LT)C4 in the synovial fluid of patients with osteoarthritis deformans (OA) and rheumatoid arthritis (RA) was measured by radioimmunoassay (RIA) after extraction with Sep-Pak C18 cartridge. The amounts of immunoreactive LTC4 (i-LTC4) in samples from patients with OA and RA were not significantly different, being 0.198 +/- 0.018 pmol/ml (n = 11) and 0.179 +/- 0.016 pmol/ml (n = 12), respectively. After separation by high performance liquid chromatography (HPLC) and measurement by RIA, the levels of other sulfidopeptide LTs, such as LTD4 and LTE4, in synovial fluid from patients with RA were found to be significantly higher than those in fluid from patients with OA. The leukocyte number in synovial fluids did not correlate with the i-LTC4 level. The metabolic activities of these synovial fluids were determined by incubating them with 3H-LTC4 and then separating sulfidopeptide LTs by HPLC. The conversion of LTC4 to LTD4 in synovial fluids of patients with OA and RA were similar, but the dipeptidase activity converting LTD4 to LTE4 was higher in fluid from patients with RA. It is suggested that a high level of LTE4 may contribute to exudation of synovial fluid, since LTE4 increases vascular permeability.

In a model of mouse embryo fibroblasts in culture, which is characterized by a very rapid decrease in rate of cell proliferation during early passages, we determined the production of prostanoids either by following the transformation of the radioactive precursor [14C]-arachidonic acid or by radioimmunoassays. Our results demonstrate that mouse embryo fibroblasts in culture produce spontaneously substantial amounts of PGE2 and 6ketoPGF1 alpha as well as trace amounts of PGF2 alpha and of lipoxygenase derivatives (Hetes). We investigated the stability of the different types of prostaglandins produced. We showed that 6ketoPGF1 alpha and PGF2 alpha were stable in vitro, whereas PGE2 as a consequence of its solubilization in an aqueous medium was metabolized by 50% over a 24 h period, independently of the presence of the cell, thus leading to a constant underestimation of real PGE2 concentration. However, comparison of the patterns of prostaglandin production among subcultures of different orders was possible, and showed that the total amount of prostaglandin produced as well as the relative proportions are fairly identical during the first three passages, although the cell proliferation pattern rapidly decreases among the serial subcultures. These results suggest that prostaglandin production does not represent in our experimental model an autocrine means of regulating cell growth.

Radioimmunoassay measurements of prostaglandins (PGs) E2, F2 alpha, 6-keto-PGF1 alpha and thromboxane (Tx) B2 in 24 h urine specimens from a male and a female healthy volunteer on several consecutive days revealed a dramatic increase of PGE2, PGF2 alpha, 6-keto-PGF1 alpha on days, upon which they had sexual intercourse; only TxB2 remained stable. Furthermore, the PGE2/PGF2 alpha ratio rose to values greater than 0.5 on days with sexual intercourse. This was found to be due to contamination of the urine samples by seminal fluid. Two 24 h urine samples from each of 26 healthy male and female volunteers (HV) revealed higher (p less than 0.01) mean PGE2 and PGF2 alpha values in males than in females. The results show that the interpretation of the urinary PG excretion as a measure of renal PG synthesis should be considered carefully, and that a PGE2/PGF2 alpha ratio greater than 0.5 indicates probable seminal contamination of urine.

The role of prostacyclin in mediating the increase in pulmonary blood flow caused by an increase in oxygen tension in the fetal lamb was investigated. Plasma concentrations of 6-keto-PGF1 alpha, the hydrolysis product of prostacyclin, were measured during an increase in pulmonary blood flow caused by a rise in oxygen tension in eight intrauterine fetal lambs. Fetal oxygen tension was increased by placing the pregnant ewes in a hyperbaric chamber and having them breathe 100% oxygen at three atmospheres absolute pressure. This increased fetal PaO2 from 27 +/- 3 to 60 +/- 6 torr (mean +/- S.E., p less than or equal to 0.0001) and increased the proportion of right ventricular output distributed to the fetal lungs from 6 +/- 2 to 45 +/- 7% (mean +/- S.E., p less than or equal to 0.001). However, the fetal plasma concentration of 6-keto-PGF1 alpha did not change, 186 +/- 26 to 208 +/- 40 pg/ml (mean +/- S.E.). Indomethacin decreased plasma concentrations of 6-keto-PGF1 alpha in each of three fetuses but did not decrease the proportion of right ventricular output distributed to their lungs. The increase in pulmonary blood flow caused by an increase in oxygen tension in the fetal lamb is not associated with an increase in plasma concentrations of 6-keto-PGF1 alpha. Prostacyclin does not appear to be involved in the increase in pulmonary blood flow caused by the increase in oxygen tension at birth.