Chemical instability of 15-keto-13,14-dihydro-PGE2: the reason for low assay reliability.

The spontaneous degradation of 15-keto-13,14-dihydro-PGE2 was studied under various conditions. In aqueous media, dehydration rapidly occurred, particularly at high or very low pH. The acid catalyzed dehydration product was identified as 15-keto-13,14-dihydro-PGA2.

Stereochemistry in the formation of 9-hydroxy-10,12-octadecadienoic acid and 13-hydroxy-9,11-octadecadienoic acid from linoleic acid by fatty acid cyclooxygenase.

9-Hydroxy-10,12-octadecadienoic acid and 13-hydroxy-9,11-octadecadienoic acid are formed from linoleic acid upon incubation with the microsomal fraction of homogenates of the sheep vesicular gland (Hamberg, M. and Samuelsson, B. (1967) J.

Formation and action of prostacyclin in the isolated human umbilical artery.

The transformation of [1-14C]arachidonic acid by homogenates of human umbilical arteries was studied. The major compound formed was the stable end product of PGI2, i.e.

Prostaglandins and thromboxanes in burn injury in man.

The main urine metabolite of prostaglandin F2 alpha (5 alpha, 7 alpha-dihydroxy-11-ketotetranor-phostane-1, 16-dioic acid, PGF-metabolite) was determined by mass spectrometry (MS) and radioimmunoassay (RIA) in burned patients treated under routine conditions. The amount of the PGF-metabolite as determined by MS was 130 and 67 microgram/24 h (normal value 24 +/- 17 microgram/24 h) on days 3 and 5 respectively in one patient. In serial determinations using RIA the urine level of the PGF-metabolite was within normal values during the first days and rose to a broad peak 1-4 weeks after the injury.

A method for measurement of platelet regeneration in man.

Platelet suspensions obtained at different time intervals following a single dose of oral aspirin were incubated with [1-(14)C]-arachidonic acid and the amount of [1-(14)C]thromboxane B2 formed was determined by a double isotope technique. Since aspirin is an irreversible inhibitor of platelet cyclooxygenase and since circulating platelets do not synthesize cyclooxygenase the rate of reappearance of active cyclooxygenase determined in this way was a measure of the rate of regeneration of functioning platelets. In two subjects the regeneration half-times were 4.

Bronchial and cardiovascular actions of prostaglandin endoperoxides and an endoperoxide analogue.

Effects of PGG2, PGH2 and the endoperoxide analogue, EPA, on bronchial and vascular smooth muscle were studied in vivo and in vitro. In the cat PGG2, PGH2 and particularly EPA proved potent stimulators of airway resistance, and they were all significantly more active than PGF2 alpha. They also increased pulmonary vascular resistance but EPA alone was more active than PGF2 alpha.

Potentiation of itch and flare responses in human skin by prostaglandins E2 and H2 and a prostaglandin endoperoxide analog.

The itch and erythematous responses induced by intradermal injection of prostaglandin E2 (PGE2), the unstable prostaglandin endoperoxide PGH2 (t1/2 approximately 5 min at 37 degrees C) and the stable endoperoxide analog (15S)-hydroxy-9alpha, 11alpha-(epoxymethano)prosta-5,13-dienoic acid (EPA) were studied in volunteers. The compounds were given alone or in combination with histamine. All the compounds produced flare reaction in the skin; the order of potency was PGE2 greater than PGH2 greater than EPA.

Identification of prostaglandin D2 as a major prostaglandin in homogenates of rat brain.

Prostaglandin (PG) E2, D2, F2alpha and thromboxane B2 (TxB2) were determined in homogenates of rat brain by gas-chromatography--mass spectrometry. The level of PGD2 was 735 +/- 19 ng/g, of PGF2alpha 150 +/- 13 ng/g, of TxB2 112 ng/g and of PGE2 86 +/- 8 ng/g. The same relative proportions of cyclooxygenase products were found in incubates of unstimulated sliced rat brain.

Glucocorticoid in inflammatory proliferative skin disease reduces arachidonic and hydroxyeicosatetraenoic acids.

Psoriasis is a prototype of several common, glucocorticoid responsive, inflammatory proliferative skin diseases. Within 28 hours, glucocorticoid reduced the increased concentration of free arachidonic acid in diseased tissue. This reduction was observed prior to visible improvement of disease and may be an important molecular mechanism for the therapeutic efficacy of glucocorticoids in psoriasis and similar inflammatory diseases.

Thromboxane A2: effects on airway and vascular smooth muscle.

Thromboxane A2, an unstable compound derived from prostaglandin G2, was generated by incubation of arachidonic acid with a suspension of human platelets. The activity of thromboxane A2 relative to that of prostaglandin H2 in causing contractions of a number of smooth muscle organs were as follows: rabbit aorta, 7-20; human umbilical artery, 9-60; and guinea pig trachea, 2-12. Intravenous injection of thromboxane A2 into anaesthetized quinea pigs was followed by a pronounced increase in the tracheal insufflation pressure, potency compared to prostaglandin H2, 31-45.

Transformation of arachidonic acid and homo-gamma-linolenic acid by rabbit polymorphonuclear leukocytes. Monohydroxy acids from novel lipoxygenases.

Addition of arachidonic acid and homo-gamma-linolenic acid to a suspension of rabbit peritoneal neutrophils led to the synthesis of 5-L-hydroxy-6,8,11,14-eicosatetraenoic acid and 8-L-hydroxy-9,11,14-eicosatrienoic acid, respectively. Both hydroxy acids were found to be the main metabolites of their respective unsaturated C-20 fatty acid precursor, constituting more than 50% of the total substrate conversion. The formation of the two metabolites was not inhibted bb indomethacin, indicating that the enzymes involved were unrelated to the prostaglandin synthetase system.

Thromboxane A2 and prostaglandin H2: potent stimulators of the swine coronary artery.

Thromboxane A2 was generated by incubation of arachidonic acid with a suspension of human platelets. The filtrate contained 266 +/- 46 ng/ml (n=10) of thromboxane A2 and 25 ng/ml or less of prostaglandin endoperoxides (prostaglandins G2+H2). Thromboxane A2 was 2-10 times more potent than prostaglandin H2 and 9-102 times and 26-308 times more potent than prostaglandins E2 and F2alpha, respectively, in causing contractions of the superfused swine coronary artery.

Stimulation of renin release from rabbit renal cortex by arachidonic acid and prostaglandin endoperoxides.

The mechanism by which renal prostaglandins stimulate renin secretion in vivo is unknown. In this in vitro study we measured the effects of activation of the prostaglandin (PG) system on renin release from slices of rabbit renal cortex. The PG precursor arachidonic acid (C20:4), a natural PG endoperoxide (PGG2), two stable synthetic PG endoperoxide analogues (EPA I and II), PGE2, PGF2alpha, and two different PG synthesis inhibitors [indomethacin and 5,8,11,14-eicosatetraynoic acid (ETA)] were used to evaluate the possibility of a direct action of the cortical PG system on renin secretion.

Effects of stimulation and inhibition of the renal prostaglandin synthetase system on renin release in vivo and in vitro.

1. The prostaglandin precursor arachidonic acid (C20:4) increases plasma renin activity in the rabbit and rat when it is infused into the renal arteries. 2.

On the formation and effects of thromboxane A2 in human platelets.

Incubation of arachidonic acid and prostaglandin G2 with a suspension of human platelets led to formation of an unstable (t1/2, 41+/-7 s) compound, thromboxane A2. Thromboxane A2 induced irreversible aggregation of washed platelets and of platelets in platelet-rich plasma and caused release of serotonin and ADP from platelets in platelet-rich plasma.

A comparison of the vasodepressor effects of the cyclic effects of the cyclic endoperoxides PGG, and PGH2 with those of PGD2 and PGE2 in hypertensive and normotensive rats.

The vasodepressor actions of the cyclic endoperoxides PGG2 and PGH2 were compared with those of their products PGD2 and PGE2 using anaesthetised normotensive and genetically hypertensive rats. Given into the aortic arch of normotensives PGE2 was approximately 6 times more potent than PGH2 and 11 times more potent than PGG2 and PGD2. Hypertensive animals were 1.

Antagonism of the prostaglandin endoperoxide imhibition of hormone-stimulated adenylate cyclase by guanosine triphosphate and 5'-guanylyl-imidodiphosphate.

The prostaglandin endoperoxide prostaglandin H2 (15-hydroxy-9alpha, 11alpha-peroxidoprosta-5,13-dienoic acid) inhibits basal and hormone-stimulated adenylate cyclase in fat cell ghosts. This inhibition by prostaglandin H2 has been found to be antagonized by GTP and Gpp(NH)p. Dose response studies have shown GTP and Gpp(nh)p to be maximally effective at 3.

Metabolism of 8,11,14-eicosatrienoic acid in human platelets.

The following labeled compounds were isolated and identified after incubation of 8,11,14-eicosatrien [1-14C] oic acid with human platelets: 12-L-hydroxy-8,10,14-eicosatrienoic acid, 8,11,12-trihydroxy-9,14-eicosadienoic acid, 8,9,12-trihydroxy-10,14-eicosadienoic acid, 12-L-hydroxy-8,10-heptadecadienoic acid, prostaglandin E1, prostaglandin D1, and 8-(1-hydroxy-3-oxopropyl)-9,12-dihydroxy-10-heptadecenoic acid (thromboxane B1).

Biosynthesis of prostaglandin F2alpha from arachidonic acid and prostaglandin endoperoxides in the uterus.

Formation of prostaglandin F2Alpha in the cow and guinea pig uterus microsomes was studied using 14C-labeled arachidonic acid and prostaglandin H2. The total conversion of arachidonic acid was of a low order and underwent fluctuations during the estrous cycle of the guinea pig, being highest towards the end of the cycle. Injections of beta-estradiol-3-benzoate also resulted in higher activity of the uterine prostaglandin synthetase.