Extraction of prostaglandins from human blood

The biochemical and ultrastructural examinations in central cholinergic damage of the rat induced by the intraperitoneal administration of AF64A

Ethylcholine mustard aziridinium ion (AF64A), a synthesized cholinergic neurotoxin, was administered via intraperitoneal injection to the rat to study its effect on the central cholinergic nervous system. A single or consecutive daily injection of AF64A for 10 days resulted in a persistent reduction of acetylcholine (ACh) content in the several tested regions of the brain in the following order: hippocampus greater than cerebral cortex = striatum, the degree was the greatest in the hippocampus. Both resting and K(+)-stimulated release of ACh from the hippocampus were also significantly reduced 24 hr after a single injection of AF64A. Furthermore, daily injection of AF64A for 10 days induced a significant reduction of choline acetyltransferase (ChAT) activity in the homogenate obtained from the hippocampus but not from the cerebral cortex and striatum. ChAT activity in the crude synaptosomal fraction of the cerebral cortex was also significantly decreased. These results suggest that intraperitoneal administration of AF64A could induce cholinergic hypofunction more selectively in the nerve terminals. The high affinity choline uptake, which is located mainly on cholinergic nerve terminals, was not affected by the administration of AF64A. Any notable changes of ultrastructure in the cholinergic nerve terminals after the administration were not observed in all three regions examined. The present findings suggested that intraperitoneal administration of AF64A induces a specific damage of cholinergic nerve terminals by inhibiting ChAT activity. The cholinergic damage was most prominent in the hippocampus.

Stimulation of prostacyclin synthesis in rats treated with phenobarbital

The effect of phenobarbital treatment on the synthesis of prostacyclin in coronary vascular microsomes was studied in Sprague Dawley rats. It was found that the treatment increased the synthesis of prostacyclin by nearly 100%. The treatment also resulted in an increase in HDL and a decrease in LDL in the serum. In vitro effects of HDL and LDL on the microsomal synthesis of prostacyclin showed that the synthesis was stimulated by HDL and inhibited by LDL. Hence it appears that the increase in prostacyclin synthesis resulting from phenobarbital treatment was at least partly due to increased level of HDL and decreased level of LDL in the serum.

Effects of adenylate cyclase inhibitors, phosphodiesterase inhibitors, and dibutyryl cyclic AMP on spontaneous and various stimuli-induced acetylcholine release from guinea pig ileum myenteric plexus

In order to examine a possible contribution of cyclic AMP to acetylcholine (ACh) release from guinea pig ileum myenteric plexus, effects of adenylate cyclase inhibitors, phosphodiesterase (PDE) inhibitors and dibutyryl cyclic AMP on the spontaneous and the various stimuli-induced ACh release were investigated. A PDE inhibitor, theophylline (1 mM) increased the ACh release induced by nicotine (6.16 microM) significantly. Another PDE inhibitor, 3-isobutyl-1-methylxanthine (IBMX, 1 mM) and dibutyryl cyclic AMP (4 mM) had no effect. The adenylate cyclase inhibitors dithiobisnitrobenzoic acid (DTNB, 1 mM) and alloxan (4 mM) both decreased the nicotine-induced ACh release remarkably. PDE inhibitors increased and adenylate cyclase inhibitors decreased the high-K+-induced ACh release. Dibutyryl cyclic AMP brought about a slight but significant increase of the high-K+-induced ACh release. All the drugs failed to alter the ACh release induced by electrical field stimulation (EFS) at 10 Hz. Effects of all drugs except dibutyryl cyclic AMP on the spontaneous ACh release were the same as those on the nicotine-induced one. Dibutyryl cyclic AMP decreased it significantly. These results suggest that the cyclic AMP system is involved in the spontaneous, the nicotine-induced and the high-K+-induced ACh release and that the EFS-induced ACh release is independent of cyclic AMP.

Inhibition by pesticides of prostaglandin formation in blood platelets

Aggregation of human platelets was investigated after pre-incubation of platelet rich plasma with various pesticides of the carbamate type. Whereas N-methyl-carbamates (insecticides) inhibited the arachidonic acid induced aggregation, N-phenyl-carbamates (herbicides) had no effect. The influence of the different carbamates on aggregation coincided with their inhibition of thromboxane B2-formation. - DDE, a metabolite of the insecticide DDT, affected aggregation to a similar extent as N-methyl-carbamates. DDT, however, had no inhibitory activity.

Isolation and identification of two isomeric trihydroxy octadecenoic acids with prostaglandin E-like activity from onion bulbs (Allium cepa)

Two fractions with prostaglandin E-like activity were isolated from onion (Allium cepa) by using XAD-2 adsorption, silicic acid column chromatography and thin layer chromatography. The fractions were analyzed by gas chromatography/mass spectrometry and were characterized as isomeric mixtures of 9,10,13-trihydroxy-11-octadecenoic and 9,12,13-trihydroxy-10-octadecenoic acid, which are lipoxygenase metabolites of linoleic acid. Bio-assay, for which cascade superfusion was used and the rabbit coeliac and mesenteric arteries and the rat fundus strip were employed as assay organs, was utilized to monitor the bio-active profile throughout the isolation procedures. The activity of 1 microgram of the pharmacologically active fractions T1 and T2 was found to be equivalent to that of respectively 1.33 and 0.63 ng of prostaglandin E2.

Contribution of endogenous prostaglandins to excitation of the myenteric plexus of guinea-pig ileum: are adrenergic factors involved?

The role of endogenous prostaglandins (PGs) in the nicotine-induced contraction and release of ACh was investigated in the isolated guinea-pig ileum. A low concentration of indomethacin (IND 2.8 microM) inhibited the contraction and ACh release induced by nicotine. These inhibitory effects of IND were reversed by PGE2 at concentrations which are thought to be released spontaneously. SC-19220, a PG receptors antagonist, also inhibited the contraction and ACh release induced by nicotine. Unlike the nicotine-induced release of ACh, the potassium-induced release of ACh was unaffected by IND and SC-19220. IND was as potent in inhibiting the responses to cholinergic nerve stimulation by nicotine after treatment of the preparations with antiadrenergic agents. It is concluded that the inhibitory effect of IND does not depend on the functional integrity of adrenergic neurons and that endogenous PGs contribute directly to the modulation of myenteric plexus excitability by nicotine.

Acetylcholine release from the myenteric plexus of guinea-pig ileum by prostaglandin E1

Release of acetylcholine (ACh) by prostaglandin E1 from the nerve terminals of the guinea-pig longitudinal muscle strip was studied in order to reveal the effect of PGE1 on myenteric plexus activity. The ACh released was collected in the presence of physostigmine (2.1 microgram ml-1) and choline (0.1 microgram ml-1) at 38 degrees C. Five to 100 ng ml-1 PGE1 enhanced the release dose-dependently. The effect was maintained during the presence of PGE1 in the organ bath, while rapid tachyphylaxis was observed with the ACh-releasing action of nicotine. Tetrodotoxin or morphine almost completely inhibited the effect of PGE1 on ACh release. Hexamethonium, in a concentration which completely blocked the effect of nicotine, partially inhibited the effect of PGE1. In the late phase of nicotine action, the tissue was still sensitive to PGE1 despite the continued exposure to nicotine. These data suggest the presence in the myenteric plexus of PG receptors which can increase ACh release.

Effect of gestational age on pulmonary metabolism of prostaglandin E1 & E2

The fetus and prematurely delivered newborn lamb have high concentrations of circulating PGE2 that may play a hormonal role, particularly in maintaining the patency of the ductus arteriosus. We studied the ability of the isolated, perfused lung from immature (100 +/- 2 days gestation, +/- SEM n = 8) and near term (142 +/- 1 days, n = 10; term is 150 days) lamb fetuses to metabolize PGE2 as a function of PGE2 concentration in the perfusate. After an intra-arterial infusion of 3H-PGE2 and 14C-inulin (to act as a marker of extracellular space), the bulk of the 14C-inulin was rapidly cleared through the isolated lung and the majority of the 3H activity appeared after the 14C activity had fallen to negligible values. The 3H activity that was retained longer in the lung was primarily associated with the 15-keto prostaglandin E2 and 15-keto-13,14 dihydro prostaglandin E2 metabolites. Lungs from immature fetal lambs metabolized 25% less PGE2 than did lungs from animals near term. This is consistent with our prior observation that premature lambs have decreased plasma clearance rates (in vivo) and elevated circulating concentrations of PGE2 when compared with term newborn lambs.

The generation of prostacyclin by arteries and by the coronary vascular bed is reduced in experimental atherosclerosis in rabbits

Experimental atherosclerosis in rabbits was associated with a suppression of prostacyclin generation from exogenous arachidonic acid by the coronary vascular bed. The spontaneous formation of prostacyclin by incubated rings of mesenteric artery was also diminished. These results suggest that in atherosclerosis an impaired activity of the endothelial prostacyclin synthexizing system contributes to the intra-arterial formation of thrombi.

Comparison of the mediator release from platelets and the development of acute inflammation in rats which lack prostaglandin precursors

Rat platelet rich plasma (PRP) generates prostaglandin endoperoxide-like activity, thromboxane A2 (TXA2) and stable prostaglandins (PGs) after collagen addition. Of the stable PGs, PGE is the main product and its formation is related to the dose of collagen. Indomethacin and eicosatetraynoic acid (TYA), both cyclo-oxygenase inhibitors, inhibit TXA2 and PGE formation simultaneously. PRP of essential fatty acid deficient (EFAD) rats, however, generates far less PG-endoperoxide like activity, TXA2 and PGE, though the release of serotonin (5-HT) is unaltered. In normal rats a marked inhibition of the cyclo-oxygenase by TYA also has no effect on 5-HT release. For these 2 reasons the role of PG endoperoxides and TXA2 seems to be unimportant for the 5-HT release reaction. The diminished biosynthesis of PGs and TXA2 in EFAD PRP is not due to an impaired cyclo-oxygenase activity since addition of AA causes an equal formation of PGE in both types of PRP. The use of platelets as in-vitro model for testing anti-inflammatory activity of drugs is discussed. The results, obtained with platelets support the hypothesis that the main reason for the decreased acute inflammatory reaction in EFAD rats is a diminished supply of endogenous PG precursors.

Possible relation of prostaglandins to PMN-derived mediators of host metabolic responses to inflammation

Stimulated rabbit peritoneal polymorphonuclear leukocyte (PMN) preparations simultaneously produce prostaglandin-like material and mediators that induce metabolic alterations in experimental animals characteristic of the host's responses to inflammation. The alterations observed in rats include responses by: proteins, carbohydrates, hormones, trace metals, and total blood neutrophils. This study demonstrates a possible relationship between prostaglandins and PMN-derived substances that mediate plasma zinc depression, hepatic amino acid uptake, and increased numbers of blood neutrophils. Production of these mediators by stimulated-PMN preparations was prevented by 23 muM indomethacin or 93 muM aspirin. Conversely, morphine (2 mM or less) had no detrimental effect on production of these mediators, although, it consistently stimulated production of a substance stimulating total blood neutrophia. In addition, 2 muM prostaglandin E and F stimulated production of substances mediating hepatic amino acid uptake plasma zinc depression, respectively. At this concentration, neither prostaglandin significantly altered production of substances mediating increased numbers of total blood neutrophils. A partial-nitrogen atmosphere, dibutyryl cyclic analogs of AMP and GMP, or homogenization of the PMN had no effect on mediator production. The inhibitory effect of indomethacin and aspirin also was observed with PMN-homogenastes. These experimental observations suggest that prostaglandin synthesis has a function in production of mediators by stimulated-PMN preparations.

Nicotine stimulates prostaglandin formation in the rabbit heart

Rabbit isolated hearts were perfused according to Langendorff with Tyrode solution. Prostaglandin-like substances (PLS) in the effluent were purified and assayed on the rat stomach strip Noradrenaline (NA) in the effluent was assayed fluorimetrically. 2 Infusion of nicotine (1 muM-50 muM) caused a dose-dependent, brief increase, from 1.2+/-0.4 to maximally 8.3+/-2.1 ng/min, in the outflow of PLS from the heart. The increase was abolished by pretreatment of the heart with indomethacin. 3 Activation of nicotinic receptors in the heart with acetylcholine (ACh, 200 muM) in the presence of atropine (1 muM) also elicited an increase in the release of PLS. This release was smaller than that caused by nicotine. 4 Nicotine (50 muM) and ACh (200 muM) in the presence of atropine (1 muM) each caused a pronounced but brief release of NA into the effluent. There was no evident correlation between the ability of the drugs to cause release of PLS on the one hand, and NA on the other. 5 It is concluded that nicotine acts as a direct stimulus for the synthesis of prostaglandins in the rabbit heart.

Prostaglandin endoperoxides, serotonin and the superfused rabbit aorta: possible pitfalls in the bio-assay of rabbit aorta contracting substance (RCS)

The specificity of the isolated rabbit aorta for identification and assay of prostaglandin endoperoxides, formed during aggregation of platelet rich plasma (PRP) from rats, was investigated in the superfused organ cascade. The use of cumulative dose-response curves in this design is quicker than conventional step-wise dosing while delivering identical results. On the rabbit aorta, in contrast to the rat fundus strip, methysergide is too weak an antagonist to rule out responses due to 5-HT. After pretreatment with phenoxybenzamine, in the presence of methysergide, the rabbit aorta retains its sensitivity towards oxygenated fatty acids, while being virtually unreactive towards 5-HT. The prostaglandin endoperoxide PGH2 is more potent than prostaglandin E2 when assayed on the rabbit aorta, while on the rat fundus the situation is reversed. Combining the rabbit aorta and rat fundus strip with pre-filtration on Amberlite XAD-2 columns showed that during collagen induced aggregation rat PRP generated both a labile RCS-most probably a prostaglandin endoperoxide- and a lipophylic prostaglandin-like material, along with 5-HT.

Indomethacin-induced alterations in corticosteroid and prostaglandin release by isolated adrenocortical cells of the cat

1 The effects of purported prostaglandin synthesis inhibitors on steroid and prostaglandin (E and F) release from trypsin-dispersed cat adrenocortical cells were investigated. 2 Low indomethacin concentrations potentiated adrenocorticotrophin (ACTH)-evoked prostaglandin and steroid release, whereas higher concentrations depressed both responses to ACTH. The steroidogenic response to exogenous prostaglandin E2 was not markedly altered over a wide range of indomethacin concentrations. 3 Indomethacin enhanced basal steroid release but did not enhance basal prostaglandin E or F release. 4 5,8,11,14-Eicosatetraynoic acid (ETA) elicited a concentration-dependent inhibition of ACTH-induced steroid release, but had little effect on prostaglandin E2-induced steroid release. A high concentration of ETA inhibited prostaglandin E and F release. 5 These data are discussed in relation to the concept that prostaglandins provide a critical link in ACTH-induced corticosteroidogenesis.

Adsorption of tryptophan metabolites from physiological fluids on XAD-2 and determination by single ion monitoring

Endogenous tryptamine, 5-hydroxytryptamine, indoleacetic acid, 5-hydroxyindoleacetic and tryptophan have been recovered from urine and cerebro-spinal fluid by adsorption on XAD-2 resin (0.3 g). After adsorption of the sample on the resin, desorption with methanol provides a single fraction that contains all of these metabolites. The mass spectra of their pentafluoropropionyl derivatives show prominent ions at m/e 276 and 438 which are characteristic of indoles and 5-hydroxyindoles, respectively, a feature that allows the concurrent determination of all the components of each group by functional group analysis. A method has been developed to carry out single ion monitoring with the peak matching system of an Hitachi RMU-6H mass spectrometer. Identifications are based on the respective Kovats Indices and single ion monitoring of two characteristic ions per compound: tryptophan (m/e 276 and 347); tryptamine (m/e 276 and 289); indoleacetic acid (m/e 276 and 335); 5-hydroxytryptamine (m/e 438 and 451); 5-hydroxyindoleacetic acid (m/e 438 and 497). The method described illustrates the feasibility of assaying biogenic indoleamines and acidic metabolites, as well as their precursor amino acid on a single fraction in contrast to other standard fractionation methods. This is possible even if the mass spectrometer is not equipped with an alternating voltage accelerator provided that it has a peak matcher, although the lack of an alternating voltage accelerator requires two separate injections of the same sample, for quantification and identification; one for the indole profile and another for the 5-hydroxyindole profile. Both profiles can be verified by individual monitoring of the other confirmatory ions. With this method the use of a multiple ion detector would allow a simultaneous determination of all of these metabolites in one gas chromatograph mass spectrometer run.

Radioimmunoassay measurement of ACTH-facilitated PGE2 and PGF2alpha release from isolated cat adrenocortical cells

Prostaglandin (PG) biosynthesis by trypsin-dispersed cat adrenocortical cells was studied by radioimmunoassay (RIA). Parallel assays of incubation media using PGF2alpha and PGF1alpha antisera established that PGF2alpha is the primary PGF released by feline cortical cells. Following the reduction of PGE to PGF with sodium borohydride (NaBH4) these same two antisera were also used to identify PGE2 as the primary PGE released. RIA using a PGE antiserum confirmed the presence of PGE in the incubation medium. Steroidogenic concentrations of ACTH (50-250muU) enhanced PGE and PGF release, and indomethacin suppressed the ACTH-facilitated release. These studies provide additional evidence for ACTH-induced PG synthesis by feline cortical cells, and support the hypothesis that PGs play some role in the steroidogenic action of ACTH.

Bioassay of histamine in the presence of prostaglandins

1. An Amberlite XAD-2 column in a heated (37 degrees C) jacket was incorporated in between two banks of bioassay organs superfused with Krebs bicarbonate solution in cascade. The column removed prostaglandins, E1, E2 and F2alpha and also rabbit aorta contracting substance (RCS) and possibly slow reacting substance of anaphylaxis (SRS-A). 2. The column gave free passage to histamine in concentrations up to 3000 ng/ml. The method described improved the accuracy of histamine bioassay in the.presence of prostaglandins.