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Biomedical subjects

F A Fitzpatrick

Publications and source records attributed to F A Fitzpatrick.

At least 91 records · Page 5Linked to original sources
PubMed1983

Influence of thromboxane synthetase inhibitors on virus replication in human lung fibroblasts in vitro.

Selective modulation of cellular arachidonic acid metabolism with thromboxane synthetase inhibitors temporarily reduced the yield of viruses hosted by human lung fibroblasts in vitro. The results were similar for several viruses including type I herpes simplex virus, vaccinia, vesicular stomatitis virus, chikungunya virus, and Newcastle disease virus. Thromboxane synthetase inhibitors of different structural classes were effective and their effects were confined to cells that contain the thromboxane synthetase. Virus yields were unaltered by total inhibition of arachidonic acid oxidative metabolism or exogenous addition of prostaglandins. In contrast to most cytopathic agents, viruses destroyed host cells without stimulating prostaglandin synthesis unless interferon induction accompanied the infection in vitro. The results suggest that cellular arachidonic acid metabolism may contribute to the host defense response during virus infections.

Arachidonic Acid↗
PubMed1983

Albumin-catalyzed metabolism of prostaglandin D2. Identification of products formed in vitro.

Human albumin catalyzed the in vitro transformation of prostaglandin D2 into three novel dehydration products identified as 9-deoxy-11-keto-15 alpha-hydroxy-delta-5,9,12-prostenoic acid; 15-deoxy-11-keto-9 alpha-hydroxy-delta 5,9,12,14-prostenoic acid. Results suggest that albumin can influence, qualitatively and quantitatively, the metabolism of eicosanoids.

Biotransformation↗
PubMed1983

Sodium 5-(3'-pyridinylmethyl)benzofuran-2-carboxylate (U-63557A), a new, selective thromboxane synthase inhibitor: intravenous and oral pharmacokinetics in dogs and correlations with ex situ thromboxane B2 production.

The pharmacokinetics of a new, selective thromboxane synthase inhibitor, sodium 5-(3'-pyridinylmethyl)benzofuran-2-carboxylate were determined for single dose, bolus intravenous injections (1, 3, and 10 mg/kg); for continuous 24 hr infusions (10 and 30 micrograms/kg/min); and for oral doses of gelatin encapsulated powdered drug (3, 10, and 30 mg/kg). Drug disappeared biexponentially after intravenous administration, and plasma concentrations were proportional to the dose. Absorption of drug occurred rapidly after its oral administration; peak plasma levels occurred 1-2 hours after ingestion, and circulating drug was detectable within 30 minutes. For all experiments, inhibition of cellular thromboxane B2 production, ex situ, corresponded with plasma drug levels and its reactivation corresponded with disappearance of the drug indicating that it was not accumulated by platelets.

Administration, Oral↗
PubMed1983

Thromboxane B2 (TxB2) release following acetyl glyceryl ether phosphorylcholine (AGEPC) infusion in the rabbit.

Intravenous infusion of acetyl glyceryl ether phosphorylcholine (AGEPC) into rabbits resulted in an AGEPC dose-dependent elevation of plasma thromboxane B2 (TxB2) levels within 30 seconds. In contrast to AGEPC, the deacetylated derivative, lyso-GEPC (36.8 micrograms), did not increase intravascular TxB2 levels when similarly infused into rabbits. Intravascular TxB2 levels were maximal at 60 seconds after the infusion of 0.61 micrograms AGEPC whereas at higher doses of AGEPC (1.21-2.4 micrograms), plasma TxB2 levels were maximally elevated within 30 seconds after initiation of AGEPC infusion. These acute increases in the intravascular levels of TxB2 were accompanied by the development of thrombocytopenia, neutropenia, and basopenia which occurred concomitantly with AGEPC dose-dependent elevations in the plasma levels of platelet factor 4. Elevations in the plasma TxB2 levels returned to pre-infusion levels within 10-20 minutes after the initiation of AGEPC infusion. Thus, in vivo, one potent phospholipid, AGEPC, stimulates the production of another class of potent lipid mediators, the thromboxanes.

Animals↗
PubMed1983

Prostaglandin E2 and thromboxane B2 in cerebrospinal fluid of afebrile and febrile cat.

Levels of prostaglandin (PG) E2 and thromboxane (TX) B2, the stable metabolite of TXA2, were measured by radioimmunoassay in cerebrospinal fluid (CSF) collected from the third ventricle and the cisterna magna of conscious cats. In the absence of fever, PGE2 was usually below the threshold of the assay (0.05-0.37 ng/ml), while TXB2 was measurable in the majority of cases and its concentration was greater in the third ventricle (about 0.7 ng/ml) than in the cisterna magna (about 0.2 ng/ml). At either site, TXB2 content rose if any manipulation was required for the collection of samples. PGE2 levels increased to measurable values (max 1.1-1.4 ng/ml) during fever produced by intrathecal or intravenous administration of leucocytic pyrogen. In contrast, TXB2 concentration rose to an average of 2.2-4 ng/ml only when pyrogen (bacterial or leukocytic) was given intrathecally. Moreover, TXB2 elevation, unlike PGE2 elevation, was limited to the uprise phase of the fever. Imidazole, given either intraperitoneally (50 mg/kg) or intrathecally (3 mg), attenuated the pyrogen fever and suppressed any rise in TXB2 levels. At the same time, the drug tended to increase the PGE2 content of the CSF. Evidence was also obtained suggesting that a fraction of PGE2 is bound to CSF protein, and this event may be important to the inactivation of the compound. These findings are consistent with the concept that PGE2 is involved in the sequence of events underlying pyrogen fever. A role for thromboxane A2 in this process remains to be established.

Animals↗
PubMed1982

Albumin stabilizes leukotriene A4.

Chemical analysis of intact leukotriene A4 showed that vertebrate albumins prolonged its aqueous half-life. At pH 7.4, leukotriene A4 hydrolyzed by first order reaction kinetics with rate constants inversely proportional to the albumin concentration. The stabilizing effect of albumin varied quantitatively among different species. Certain agents, such as warfarin, that interact with the site I binding region of albumin reversed its stabilizing effect. Sequestration and exposure of leukotriene A4 to a hydrophobic, alkaline microenvironment of albumin would account for the results. The amino acid sequences Lys-Ala-Trp-Ala-Val-Ala-Arg from residues 211-217 of human albumin or Lys-Ala-Trp-Ser-Val-Ala-Arg from residues 210-216 of bovine albumin are compatible with this requirement. The persistence of leukotriene A4 in the presence of albumin confirms and extends our recent observations on its uniform and predictable influence on eicosanoid stability. The significance of this influence is uncertain; however, albumin can no longer be viewed as inert considering its capacity to modify the stability of several, structurally diverse eicosanoids.

Animals↗
PubMed1982

Comparison between circulating interferon and drug levels following administration of 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP) to different animal species.

Using a high-performance liquid chromatographic assay, these studies attempted to correlate circulating levels of 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP) with the serum interferon response induced in mice, cats, dogs, cattle, and rabbits. The order of greatest sensitivity for interferon induction by ABPP was mice greater than cats greater than dogs greater than cattle greater than rabbits. Experiments to date indicate that the circulating drug levels associated with a detectable interferon response were 10-15 microgram/ml (mice), 15-30 micrograms/ml (cats and dogs), and 30-50 micrograms/ml (cattle). Whereas rabbits produced large amounts (greater than 10(4) units/ml) of interferon when induced with Newcastle disease virus, we could not demonstrate unequivocally that rabbits were induced by ABPP even when circulating drug levels reached 50 micrograms/ml, or greater. We also observed differences in the pharmacokinetics of ABPP in the different species which may contribute to the differences described for the interferon responses. The data point out the need for cautious selection of animal models for preclinical efficacy evaluation and cautious extrapolation of data from preclinical studies to eventual clinical evaluation.

Administration, Oral↗
PubMed1982

6,9-deepoxy-6,9,-(phenylimino)-delta 6,8-prostaglandin I1, (U-60,257), a new inhibitor of leukotriene C and D synthesis: in vitro studies.

Addition of the calcium inophore, A 23187, and cysteine to isolated mononuclear cells from rat peritoneal washings causes a marked increase in the formation of thromboxane B2 (TxB2) along with the formation of leukotrienes C and D (LT's). The formation of LT's in this system was inhibited by 6,9-deepoxy-6,9-(phenylimino)-delta 6,8-prostaglandin I1, U-60,257, or its methyl ester, U-56,467, (ID50 4.6 and 0.31 microM, respectively). There was no inhibition of TxB2 formation. By contrast, two structurally-related compounds, PGI2 and its stable analog, 6-beta-PGI1, did not affect the formation of either LT's or TxB2. The inhibition of LT formation by U-60,257 was rapidly reversed after removal of this compound from the cells. U-60,257 did not inhibit the cyclooxygenase of human polymorphonuclear leukocytes. Nor did it inhibit formation of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) in human platelets. On the other hand, U-60,257 inhibited glutathione S-transferase activity of rat basophil leukemia cells (ID50, 37 microM), suggesting that this compound may inhibit the last step in LTC biosynthesis. In addition to inhibiting LT synthesis, U-60,257 also appears to be a competitive inhibitor of the action of LT on the guinea pig ileum, although this inhibition requires a higher drug concentration than those ordinarily encountered during assay for LT's in U-60,257-treated incubations.

Animals↗
PubMed1982

A radioimmunoassay for the unstable pulmonary metabolites of prostaglandin E1 and E2: an indirect index of their in vivo disposition and pharmacokinetics.

The peripheral plasma content of the pulmonary metabolite, 13,14-dihydro-15-keto-prostaglandin E2, reflects prostaglandin E2 (PGE2) biosynthesis and disposition in vivo more reliably than the peripheral plasma content of PGE2 itself. However, the chemical instability of 13,14-dihydro-15-keto-PGE2 and the multiple fates of its degradation products hinder the development of quantitative assays for the metabolite. We eliminated these problems with an indirect approach. At pH 10.5, intact 13,14-dihydro-15-keto-PGE2 and its degradation products convert uniformly into 11-deoxy-13,14-dihydro-15-keto-11 beta, 16 xi-cyclo-PGE2. We developed a radioimmunoassay with a sensitivity of 12-pg for this analytically suitable bicyclic derivative. The accuracy, precision and sensitivity of the method permitted its application to certain intractable problems. For example, plasma levels of the pulmonary metabolite can be quantitated and used as an index of the pharmacokinetic disposition of PGE2 because its metabolite forms almost instantaneously and completely, in vivo. In dogs, there was a dose-dependent increase in plasma 13,14-dihydro-15-keto-PGE2 concentrations after bolus i.v. injections of PGE2. Ten minutes after administration of 30, 10 or 3 micrograms of PGE2 per kg, its plasma metabolite concentrations were 34.1 +/- 8.4, 6.8 +/- 0.6 and 2.0 +/- 0.2 ng/ml (mean +/- S.E.M., n = 4). the metabolite disappeared from the circulation rapidly with half-lives of 9.9 +/- 0.2, 9.2 +/- 0.3 and 7.8 +/- 0.8 min (mean +/- S.E.M., n = 4) for the respective doses noted above. Similar studies with PGE1 were possible because of the predictable cross-reaction between the bicyclic derivatives of 13, 14-dihydro-15-keto-PGE2 and 13,14-dihydro-15-keto-PGE1. Because the latter compound is not normally present in mammals, measurements of endogenous 13,14-dihydro-15-keto-PGE2 are still accurate. Basal concentrations of 48 +/- 31 pg/ml (mean +/- S.D., n = 15) in human plasma concur with concentrations measured by gas chromatography/mass spectrometry.

Alprostadil↗
PubMed1981

Albumin-lipid interactions: prostaglandin stability as a probe for characterizing binding sites on vertebrate albumins.

We determined the effect of vertebrate albumins on the stability of several physiologically relevant prostaglandins. All naturally occurring prostaglandins with beta-hydroxy ketone group decomposed by first-order kinetics, dependent on the albumin concentration in 0.1 M, pH 7.4, buffer at 37 degrees C. Even subphysiological levels of albumin (1-20 mg/mL) significantly reduced the stability of these compounds in vitro. The prostaglandins with a beta-hydroxy ketone responded to albumin in the order of their intrinsic stability; namely, less stable compounds were more susceptible. The destructive effect of albumin was nearly maximal at a 1:1 mole ratio of albumin (20 mg/mL):prostaglandin (100 micrograms/mL). Albumin had no destructive effect on prostaglandins without a beta-hydroxy ketone. Albumins from different vertebrates varied in destructive severity, but all were effective. Near neutrality, in the absence of albumin, decomposition of E-type prostaglandins was practically suspended at the dehydration stage. In the presence of albumin, dehydration was accompanied by rapid isomerization reactions (e.g., PGA1 leads to PGB1) that occur only at an elevated pH. The results suggest that albumin sequesters prostaglandins to one principal binding site and exposes them to its associated highly alkaline microenvironment. This results in a uniform and predictable influence on prostaglandin stability. Our proposed model system successfully reconciles apparently anomalous or contradictory reports regarding the effect of albumin on prostaglandin stability.

Animals↗
PubMed1981

Anaphylactic release of thromboxane A2, prostaglandin D2, and prostacyclin from human lung parenchyma.

Antigen challenge of passively sensitized chopped human lung resulted in the generation of several arachidonic acid cyclooxygenase metabolites (AACM): thromboxane A2 (TxA2) as measured by its stable metabolite TxB2, prostaglandin D2 (PgD2), prostacyclin (PgI2) as measured by its stable metabolite 6-keto-PgF1 alpha, prostaglandin F2 alpha (PgF2 alpha), and prostaglandin E (PgE). The kinetics of AACM release after antigen challenge paralleled histamine release. All AACM were released in an antigen dose-dependent manner and reached maximal release at antigen concentrations lower than those required for maximal histamine release. Quantitatively, of the AACM measured, PgD2 and PgI2 were found to predominate in anaphylactic reactions of human lung parenchyma. Generation of PgD2 and PgI2 were 3- to 7-fold greater than that of other AACM measured. Thromboxane B2 was generated in quantities comparable to PgE and PgF2 alpha. Studies were designed to test the hypothesis that lung smooth muscle contraction per se can account for the generated AACM that are released during anaphylaxis of the lung. The studies compared antigen-induced AACM generation with methacholine-induced (10(-4) M) AACM generation. The failure to confirm this hypothesis was especially evident for PgD2 where release was dependent on mast cell activation. Thromboxane A2, PgD2, and PgI2 have been reported to have potent effects on smooth muscle. Our data suggested that these AACM are generated in such sufficient quantities that they may function in important aspects of the modulation of hypersensitivity responses in human lungs.

Anaphylaxis↗
PubMed1981

Acetyl glyceryl ether phosphorylcholine. Intravascular alterations following intravenous infusion into the baboon.

The intravenous infusion of 1-O-hexadecyl/octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC) in baboons (28 micrograms per kg.) induced acute, but reversible, thrombocytopenia and neutropenia and the intravascular release of platelet factor 4 and thromboxane B2. Maximal depression of circulating platelets and neutrophils occurred within 30 seconds after AGEPC infusion and was accompanied by significant elevations in plasma platelet factor 4 and thromboxane B2 levels (p less than 0.02). Hematocrit values increased after AGEPC infusion, but this increase was delayed relative to the other intravascular alterations, i.e., maximal hematocrit values occurred at 10 to 20 minutes after AGEPC infusion.. The thrombocytopenia induced by AGEPC was reversed within 2 to 3 minutes; in contrast, circulating neutrophils did not return to preinfusion levels until 30 minutes after AGEPC infusion. Plasma platelet factor 4 and thromboxane B2 elevations gradually decreased and returned to preinfusion levels within 30 to 60 minutes. The deacetylated derivative of AGEPC, lyso-glyceryl ether phosphorylcholine, had no effect when similarly infused into baboons. These studies demonstrate that the intravenous administration of AGEPC into baboons initiated significant but reversible intravascular alterations; thus, this unusual acetylated alkyl phosphoglyceride may be an important mediator of inflammation in primates, including man.

Animals↗
PubMed1980

The stability of 13,14-dihydro-15 keto-PGE2.

13,14-Dihydro-15 keto-PGE2 decomposes by first order reaction kinetics, dependent on pH, temperature and albumin concentration. Under common experimental conditions at or near neutrality in the absence of albumin decomposition is suspended with the formation of 13,14-dihydro-15-keto-PGA2. Cyclization into 11-deoxy-13,14-dihydro-15 keto-11,16-bicyclo-PGE2 occurs at elevated pH in purely aqueous buffers, and also at or near neutrality in the presence of albumin. Albumin accelerates, quantitatively, the decomposition of 13,14-dihydro-15 keto-PGE2 and promotes, qualitatively, the formation of the bicyclo rearrangement product. High performance liquid chromatographic analysis indicates that the cyclization product exists in at least three epimerically distinct forms. The two major epimers have been synthesized and isolated in pure form. They differ, mainly, by their optical rotation.

Albumins↗