Immunoreactive Plasma Research Articles

Differences in the neuropeptide Y-like immunoreactivity of the plasma and platelets of human volunteers and depressed patients.

In this study, patients with recurrent major depression were found to have significantly lower neuropeptide Y-like immunoreactivity (NPY-LI) in platelet-poor plasma (p < 0.01) and significantly higher NPY-LI in platelets (p < 0.001) compared to controls. Also, qualitative differences in the NPY-LI in platelet-poor plasma (PPP) and platelets were detected when the samples were analyzed by HPLC followed by RIA of the collected fractions.

Relationship between the number of immunostaining gonadotropes and the plasma concentrations of gonadotrophins in ewes with and without the FecBB gene.

Booroola ewes possess a major gene, FecBB, that influences their ovulation rate (number of ovulations per oestrous cycle). Homozygous (BB) carriers of the FecBB gene have higher plasma concentrations of FSH and sometimes LH relative to the non-carriers (++). The aim of this study was to determine whether the plasma concentration differences in FSH or LH between the genotypes were due to a greater number of FSH beta- or LH beta-immunostaining cells in the anterior pituitary gland of BB ewes during the luteal phase of the oestrous cycle. No differences were found between the BB (n = 7) ewes and ++ (n = 8) ewes in total number of pituitary cells, pituitary volume, numbers or diameters of FSH beta- or LH beta-immunostaining cells, notwithstanding significantly higher concentrations of immunoreactive plasma FSH (P < 0.001) but not LH in BB compared with ++ animals. Significant linear relationships were found within each genotype between plasma FSH and number of FSH beta-immunostaining cells. No such relationship was found for plasma LH and number of LH beta cells. For the FSH relationship, the slopes of the regression lines were the same. It is hypothesized that the differences in plasma concentration of FSH between the genotypes is due to a greater output of FSH per pituitary cell in the BB animals.

Release of β-endorphin immunoreactivity into ventriculo-cisternal perfusate by lumbar intrathecal capsaicin in the rat

A model employing perfusion of artificial cerebrospinal fluid from the lateral ventricle to the cisterna magna in the halothane anesthetized rat was used to study β-endorphin release in the brain. Injection of 75 μg capsaicin into the lumbar intrathecal space released β-endorphin immunoreactivity into perfusate. The release was blocked by intrathecal pretreatment with 1.25 mg lidocaine and the capsaicin receptor antagonist capsazepine (92 μg), showing that the release is caused by binding of capsaicin to a spinal receptor. The release was also blocked by intrathecal pretreatment with the NMDA antagonist MK-801 (3 μg) and the NK-1 receptor antagonist CP96,345 (200 μg) , whereas the AMPA receptor antagonist NBQX (6 μg) yielded no significant inhibition. Surprisingly, morphine (30 μg) and sufentanil (1.5 μg) did not prevent release of β-endorphin immunoreactivity, although blocking the cardiovascular responses to a noxious heat stimulus. High performance liquid chromatography characterization of perfusates collected after capsaicin injection showed that all β-endorphin immunoreactivity coeluted with authentic β-endorphin 1–31. β-Endorphin immunoreactivity in plasma was increased 10 min, but not 25 min, after capsaicin injection. Capsaicin injection abolished the motor and cardiovascular responses to tail immersion in 52.5°C water. Addition of MK-801 (10 −4 mol/1) to the lateral ventricle-cisterna magna perfusate blocked the capsaicin-induced β-endorphin release, showing that our previous demonstration of an NMDA receptor regulating arcuate nucleus β-endorphin neuron activity has functional significance. We conclude that in this in vivo, anesthetized preparation including three hot water tail immersions, β-endorphin can be released into a ventriculo-cisternal perfusate, by activation of the central axons of small primary afferent neurons by capsaicin. These data support the idea that central β-endorphin may be released in response to prolonged, intense noxious stimulation.

Augmented adrenomedullin concentrations in right ventricle and plasma of experimental pulmonary hypertension

Adrenomedullin is a strong vasorelaxing peptide discovered in pheochromocytoma tissue. Monocrotaline, a pyrrolizidine alkaloid derived from Crotalaria spectabilis, is known to cause pulmonary hypertension. To test the hypothesis that adrenomedullin plays a role similar to that of atrial natriuretic peptide or brain natriuretic peptide in modulating right ventricular responses to pulmonary hypertension, we have compared concentrations of immunoreactive rat adrenomedullin and adrenomedullin messenger RNA levels in tissues of monocrotaline treated rats with those of control rats. We also measured the effect of pulmonary hypertension on plasma level of the peptide. The concentrations of adrenomedullin immunoreactivity in right ventricle and plasma were significantly higher in monocrotaline treated rats than in control rats. The messenger RNA level of adrenomedullin in right ventricle was also higher in monocrotaline treated rats than in control rats. These results suggest that adrenomedullin participates in the mechanism to counteract the high blood pressure in pulmonary circulation.

Immunometric assays of luteinizing hormone (LH): differences in recognition of plasma LH by anti-intact and beta-subunit-specific antibodies in various physiological and pathophysiological situations

Restricted immunoreactivity of plasma luteinizing hormone (LH) has been described in some subjects when assayed with certain methods involving antibodies against intact LH. We have compared the performance of the Amerlite LH-30 (A) and Delfia LHSpec (D) assays (which include anti-intact and beta-specific antibodies, respectively) in normal and pathological conditions. As shown previously, results of the two systems were highly correlated with each other and, as we show here, with those of a bioassay. We found eight outliers (results outside the 95% confidence interval of the regression) among 427 samples studied from 121 subjects. Of the outliers, five had Delfia results in a range (< 1 IU/L) that was associated with poor assay precision for that assay, and the ratios of their values by both methods (A:D ratios) were very low. This ratio was affected by endocrine status, e.g., was lower in postmenopausal women than in premenopausal controls, and varied intraindividually within the same menstrual cycle. The restricted immunoreactivity described previously for assays involving anti-intact LH antibodies may, in part, reflect these differences, which, in turn, may reflect the presence of isoforms (e.g., glycoforms) that are differentially recognized by assays that have different antibody configurations.

Comparison of sandwich enzyme-linked immunoadsorbent assay and radioimmunoassay for determination of exogenous glucagon-like peptide-1(7–36)amide in plasma

A sensitive sandwich enzyme-linked immunoadsorbent assay (ELISA) for determination of exogenous glucagon-like peptide-1(7–36)amide (GLP-1(7–36)amide) in plasma samples from pharmacokinetic studies is described. The assay employs an N-terminally directed antibody and a C-terminally directed antibody. The ELISA has a working range from 10 to 500 pmol 1 −1, and can be applied to plasma samples from humans, dogs, pigs, minipigs, cats, rabbits, and rats. The assay was compared to a validated radioimmunoassay (RIA), employing an antibody directed against the mid-region of GLP-1. After s.c. administration of GLP-1(7–36)amide, the plasma immunoreactivity of GLP-1 (P-GLP-1-IR) measured by ELISA was markedly lower than P-GLP-1-IR measured by RIA. After HPLC fractionation of plasma samples with subsequent RIA and ELISA analyses of the fractions, this difference was shown to be due to cross reaction with biologically inactive fragments of GLP-1(7–36)amide in the RIA but not in the ELISA.

Release of beta-endorphin immunoreactivity from brain by activation of a hypothalamic N-methyl-D-aspartate receptor.

Lateral ventricle-cisterna magna perfusion in the halothane-anesthetized rat was used as a model to study beta-endorphin release in the brain. Microinjection of N-methyl-D-aspartate into the arcuate nucleus of the hypothalamus released beta-endorphin immunoreactivity into perfusate and the release was blocked by systemic pretreatment with the N-methyl-D-aspartate antagonist dizocilpine (MK-801). N-methyl-D-aspartate microinjections did not increase beta-endorphin immunoreactivity in plasma, and pretreatment with dexamethasone did not prevent release of beta-endorphin immunoreactivity into perfusate, emphasizing that the released beta-endorphin immunoreactivity did not come from plasma. The non-N-methyl-D-aspartate glutamate receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide did not release beta-endorphin immunoreactivity. High-performance liquid chromatography characterization of perfusates collected after N-methyl-D-aspartate microinjection showed that a major part, but not all, of the beta-endorphin immunoreactivity co-eluted with authentic beta-endorphin. Microinjection of N-methyl-D-aspartate provoked an algogenic response in the anesthetized rat, and inhibited the motor and cardiovascular responses to tail immersion in 52.5 degrees C water. This block was reversed by pretreatment with MK-801, but not naloxone. Injection of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid hydrobromide elicited the same behavioral response and blocked the nociceptive tail-dip reaction, but did not release beta-endorphin immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathoadrenal Responses to Bronchoconstriction in Asthma: An Invasive and Kinetic Study of Plasma Catecholamines

1. Bronchoconstriction does not seem to be a stimulus for sympathoadrenal activation, as judged by venous plasma concentrations of noradrenaline, adrenaline or neuropeptide Y-like immunoreactivity. However, venous measurements have methodological drawbacks. In the present study arterial and mixed venous (pulmonary arterial) levels of these variables were determined before and after histamine-induced bronchoconstriction in non-medicated asthmatic subjects. In addition, noradrenaline kinetics in plasma (isotope dilution) and the pulmonary overflows of noradrenaline and neuropeptide Y-like immunoreactivity were determined. 2. Histamine inhalation induced bronchoconstriction; forced expiratory volume in ls decreased by 38.7% +/- 4.1% (SE) and arterial PO2 by 3.0 +/- 0.9 kPa. This acute bronchoconstriction induced significant elevations of arterial and mixed venous plasma noradrenaline from < or = 1.18 nmol/l to > or = 1.40 nmol/l. The clearance of NA from plasma increased marginally. Thus, the arterial plasma NA response was due to increased spillover of noradrenaline to plasma (from 1.80 +/- 0.18 to 2.52 +/- 0.36 mmol min-1/m2 at maximal bronchoconstriction, with a subsequent further increase). There were no elevations of adrenaline or neuropeptide Y-like immunoreactivity in arterial plasma. 3. No sympathetic activation could be demonstrated in the lungs (pulmonary noradrenaline or neuropeptide Y-like immunoreactivity overflow), and no alterations in pulmonary vascular resistance or cardiac output were observed. Neither arterial nor mixed venous plasma concentrations of adrenaline were influenced by bronchoconstriction. 4. Acute bronchoconstriction thus leads to peripheral sympathetic activation (possibly due to the increased work of breathing) which does not involve the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoreactive tachykinins in 24-h collections of urine from patients with carcinoid tumours: characterization and correlation with plasma concentrations.

Tachykinins are a family of peptides that may be present in and secreted from carcinoid tumours of mid-gut origin. They are likely to play a role in the pathogenesis of, e.g. the flush, dyspnoea and valvular heart disease seen in the carcinoid syndrome. Since tachykinins are secreted from the tumour into the circulation in bursts, coinciding with flushing attacks, and have short half-lives, we anticipated that analysis of 24-h urine excretion of immunoreactive tachykinin metabolites might prove to be a more sensitive and stable parameter for monitoring than tachykinin-like immunoreactivity in plasma. The study included 48 patients hospitalized for treatment of advanced carcinoid tumours and 32 healthy controls. The urine excretion of tachykinin-like immunoreactive metabolites in the carcinoid patients (median 27.5 pmol 24 h-1, interquartile range (IQR) 8.5-51.0 pmol 24 h-1) was significantly (p<0.001) higher than that in the 32 healthy subjects (median 3.0 pmol 24 h-1, IQR 0.9-4.20 pmol 24 h-1). Of the patients, 38 (79%) had elevated 24-h urine excretion of tachykinin-like immunoreactive metabolites while 31 (64%) had elevated plasma concentrations of tachykinin-like immunoreactive metabolites. Of the patients, 27 (56%) had elevated concentrations of tachykinin-like immunoreactive metabolites both in plasma and urine, 12 (25%) had elevated concentrations only in urine excretion, 3 (6%) had elevated concentrations of only plasma tachykinin-like immunoreactive metabolites and 7 (14%) had elevation of neither plasma nor urine concentrations. Analysis by means of different column chromatographic techniques indicated that the immunoreactive material was heterogeneous, with some components co-eluting with oxidized neurokinin A (NKA) and neuropeptide K (NPK). The urine tachykinin-like immunoreactivity correlates well with that of plasma, but is a slightly more sensitive indicator of elevated tachykinin-like immunoreactivity, probably since levels of urine tachykinin-like immunoreactive metabolites reflect the overall amount of the latter secreted into the circulation during 24 h.

Neuropeptide FF-like immunoreactivity in human plasma

In order to examine whether neuropeptide FF (NPFF), an octapeptide with pain-modulating and blood pressure-raising properties in the rat, is present in circulating human blood, a radioimmunoassay (RIA) was established. Using this highly specific and sensitive RIA, the mean concentration of NPFF in human plasma was 2.9 pg/ml ± 1.1 ( n = 111). The concentration did not correlate with age or sex. Reversed-phase high pressure liquid chromatography (HPLC) followed by RIA using two different antisera for NPFF showed that plasma NPFF eluted in a position identical to that of synthetic NPFF. In view of published K d values (0.06 m M) for NPFF receptor, the concentrations detected of NPFF in human plasma may be too low for systemic actions. Thus, plasma NPFF may represent leakage of the peptide from nervous tissue.

Inhibitory effects of diclofenac on the endotoxin shock response in relation to endothelin turnover in the pig

During sepsis vasoactive arachidonic acid metabolites of the cyclo-oxygenase pathway and the endothelium-derived vasoconstrictor endothelin-1 (ET-1) are released. The effects of cyclo-oxygenase pathway inhibition by diclofenac on the endotoxin shock response and ET-1 turnover, were investigated in five groups of pigs. In the first group (n = 7; controls) endotoxin (15 micrograms.kg-1.h-1 i.v.) was infused for two hours. In a second endotoxin group (n = 7), the animals were pretreated with diclofenac (3 mg.kg-1 i.v.). In a third group (n = 7), high-dose ET-1 was infused (20 pmol.kg-1.min-1 i.v.) and in a fourth group (n = 7), the ET-1 infusion was preceded by diclofenac. In a fifth group (n = 4), a low and intermediate dose of ET-1 (0.2 and 4 pmol.kg-1.min-1) was infused. A significant increase in ET-1-like immunoreactivity (LI) plasma levels was observed in both endotoxin groups, but in the diclofenac group the increase was comparatively delayed. Furthermore, this group showed a more stable haemodynamic course and in the biphasic increase of pulmonary vascular resistance seen in endotoxin controls, the initial peak was abolished by diclofenac. Exogenous ET-1 infusion indicated that not only locally released but possibly also circulating ET-1 could be a mediator of vascular responses to endotoxin. Indications of release from the lungs were seen during endotoxin infusion. Diclofenac had no effect on basal ET-1-LI plasma levels or on the disappearance rate from plasma of ET-1-LI and the haemodynamic changes seen on ET-1 infusion. The inhibition of cyclo-oxygenase pathway by diclofenac resulted in prevention of the initial pulmonary hypertension and a delayed increase in plasma ET-1-LI levels in porcine endotoxin shock and this latter effect is not due to an increased rate of disappearance from plasma but rather to a decreased release of ET-1.

Deconvolution Analysis of Spontaneous Nocturnal Growth Hormone Secretion in Prepubertal Children with Preterminal Chronic Renal Failure and with End-Stage Renal Disease

We sought to determine whether elevated circulating growth hormone (GH) concentrations in uremic prepubertal children are due to an increase in GH secretory activity by the pituitary gland or a decrease in the metabolic clearance of GH consequent to reduced GFR. Deconvolution analysis was applied to the nighttime plasma GH profiles of 1) 11 children with preterminal chronic renal failure, 2) 12 children with end-stage renal disease (ESRD), and 3) a control group of matched children with idiopathic short stature (n = 12). Mean (+/- SEM) half-life of endogenous GH in children with ESRD (27.5 +/- 2.7 min) and preterminal chronic renal failure (23.1 +/- 2.1 min) was significantly higher than in controls (14.8 +/- 1.6 min; p < 0.001). GH half-life correlated inversely with GFR (r = -0.65, p < 0.001). The number of GH secretory bursts/10 h in ESRD (8.1 +/- 0.4) was amplified compared with preterminal chronic renal failure (6.4 +/- 0.5) and with controls (5.9 +/- 0.4; p < 0.005). GH production rate varied over a broad range in the three groups: It was highest in ESRD (202 +/- 56.6 microgm/L/10 h; range 36-683), mainly as a result of an increased number of GH secretory bursts, and not statistically different in preterminal chronic renal failure (66.2 +/- 11.4 microgm/L/10 h; range 25-168) and in controls (129 +/- 27.7 microgm/L/10 h; range 39-392). Increased GH half-life, in concert with an increased GH production in some individuals with ESRD, leads to a 2.5-fold increase in the mean plasma GH concentration in ESRD compared with the two other groups (p < 0.005) [corrected].(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of endothelin-1 immunoreactivity in plasma, cerebrospinal fluid and urine.

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide apparently involved in a number of vascular diseases in man. Nonetheless, its determination in biological samples is difficult, and data on plasma or urine concentrations are controversial. We investigated different sample preparation procedures as well as different radioimmunoassays for their influence on ET-1 measurement. Recovery of ET-1 depended on the extraction procedure, the type and size of the extraction columns and on the biological matrix itself. Incomplete removal of matrix components by the extraction leads to the formation of particulate matter in the evaporated eluate. When dissolved in assay buffer, ET-1 was found to be absorbed to and only partly released from these particulates, so that it was not accessible for measurement in a radioimmunoassay. This was the case for all extraction procedures investigated except for that involving acetic acid. HPLC analysis of spiked samples revealed that ET-1 is in part degraded during extraction, most probably to Meth-sulphoxide ET-1. Dilution curves of synthetic pure ET-1 standards from different suppliers, prepared either in plasma with subsequent extraction or in assay buffer of the respective radioimmunoassay, resulted in considerable differences in the measured values for ET-1-immunoreactivity. Every radioimmunoassay tested had a specific pattern of recognizing different synthetic ET-1 standards. In conclusion, the measurement of ET-1-immunoreactivity is strongly influenced by the experimental conditions of sample preparation as well as by the radioimmunoassay employed.

Circulating fibroblast growth factor-like autoantibodies in two patients with multiple endocrine neoplasia type 1 and prolactinoma.

Basic fibroblast growth factor (bFGF) is a potent endothelial cell mitogen found in a variety of normal and tumor tissues. bFGF lacks a classical amino-terminal signal sequence and is not readily detectable in plasma from normal subjects. In earlier studies we showed increased bFGF-like mitogenic activity for parathyroid-derived endothelial cells and (increased) bFGF immunoreactivity (0.24-1.28 ng/mL) in plasma of subjects with multiple endocrine neoplasia type 1 (MEN-1). In the present study we examined the proliferative activity of MEN-1 and normal plasmas (applied to protein-A columns) in calf pulmonary artery endothelial cells. Protein-A-eluted activity in plasma from MEN-1 prolactinoma plasma exceeded activity from normal and MEN-1 nonprolactinoma plasma in three of eight MEN-1 subjects with untreated or recurrent prolactinoma. Protein-A-eluted active fractions from MEN-1 prolactinoma plasma had several properties of an immunoglobulin G, including affinity for antihuman immunoglobulin G (IgG) agarose, sensitivity to thiols, and (prepared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions) apparent mol wt corresponding to those of the heavy and light chains of IgG. The IgG fraction of MEN-1 prolactinoma plasma had far more activity in endothelial cells than did optimal concentrations of known growth factors or conditioned medium from prolactinoma cells. Endothelial cell bioactivity in protein-A-eluted fractions from MEN-1 prolactinoma plasma was neutralized 70% by rabbit antibodies to intact bFGF. These results imply novel growth stimulatory bFGF-like autoantibodies in a subset of MEN-1 patients with prolactinoma.

Pancreatic Expression and Secretion of Human Islet Amyloid Polypeptide in a Transgenic Mouse

Islet amyloid polypeptide (IAPP) is a secretory product of the pancreatic beta-cell, which is the primary constituent of the islet amyloid that develops in type II diabetes. To study the role the inherent amyloidogenicity of human IAPP (hIAPP) plays in the formation of islet amyloid deposits and to investigate a possible hormonal role for IAPP, transgenic mice expressing hIAPP were developed. The transgene was composed of a fragment of an hIAPP cDNA linked to the rat insulin II promoter. One line of transgenic mice expressed the transgene and synthesized hIAPP in their pancreatic islets. IAPP-like immunoreactivity in pancreatic extracts and plasma were two- to threefold greater in the transgenic mice compared with nontransgenic control mice. Although plasma concentrations of immunoreactive insulin (IRI) and glucose were equal in transgenic and control mice, the pancreatic content of IRI was nearly twofold greater in the transgenic animals, and proinsulin mRNA was significantly elevated, suggesting increased rates of insulin biosynthesis. Pancreatic samples obtained from transgenic mice up to 19 months of age had no evidence of islet amyloid. These results indicate that an increased level of synthesis of the amyloidogenic hIAPP is not sufficient to cause islet amyloid deposition. However, the increased synthesis and storage of insulin in the islets of the transgenic mice are consistent with either a direct regulatory effect of IAPP on the beta-cell or indirect stimulation of insulin production through IAPP-induced insulin resistance.

Effects of a sustained release formulation of thyrotropin-releasing hormone on behavioral abnormalities in senescence-accelerated mice

Effects of a sustained release formulation of thyrotropin-releasing hormone (TRH-SR) on reduced anxiety-like behavior and learning impairment in senescence-accelerated mice (SAM) were examined. SAMP8/Ta (SAMP8) mice showing age-related emotional changes as well as learning and memory impairments, and SAMRITA (SAMR1) mice exhibiting normal aging were used at 8 months of age. Subcutaneous injection of TRH-SR (2.8 mg/kg as free TRH) produced a sustained increase in immunoreactive plasma TRH levels up to about 4 weeks after dosing in SAMP8. TRH-SR antagonized the reduced neophobia to novel food in SAMP8 in a dose-dependent manner when tested 10 days but not 3 days after the injection. In the elevated plus-maze test, the SAMP8 control group treated with vehicle had significant increases in the number of entries into open arms and the time spent in open arms in comparison to SAMR1 mice. TRH-SR showed dose-dependent decreases in the number of entries into open arms, and reduced the time spent in open arms in SAMP8 mice. Furthermore, TRH-SR significantly improved the impairment of water maze learning in SAMP8 mice. In contrast, bolus administration of TRH had no significant effects on behavioral abnormalities in SAMP8 even at high doses, implying that long-term and continuous infusion of TRH may be important for amelioration of the behavioral abnormalities. These results suggest that TRH-SR may be useful for treatment of age-related emotional disorders and memory disturbance in dementia.

Angiotensin II metabolic clearance rate and pressor responses in nonpregnant and pregnant women

Normal pregnancy is associated with reduced pressor dose-responses to infused angiotensin II. We tested the hypotheses that alterations in the metabolic clearance rate and the half-life of angiotensin II account for reduced pressor dose-responses during gestation and that angiotensin II increases circulating levels of vasodilatory prostaglandins I2 and E2 relative to thromboxane A2. Eleven nonpregnant and 37 pregnant (30 +/- 0.3 weeks' gestation, mean +/- SE) women were infused with angiotensin II (3.11 to 22.36 ng/min.kg) for 15 minutes, and blood was obtained to evaluate steady-state immunoreactive plasma angiotensin II and eicosanoid concentrations. Angiotensin II pressor responses were dose dependent in all groups and reduced in pregnant women (p < 0.001). Basal immunoreactive plasma angiotensin II concentrations were 2.7-fold greater (p < 0.001) in pregnant versus nonpregnant women. Plasma levels reached steady state by 5 minutes of infusion, and at similar angiotensin II concentrations the increase in blood pressure was greater in nonpregnant versus pregnant women (p < 0.001). The angiotensin II metabolic clearance rate and half-life were similar in nonpregnant and pregnant women: metabolic clearance rate = 85 +/- 10 versus 68 +/- 3 ml/min.kg, respectively (p = 0.130), and half-life = 48 and 49 seconds, respectively. Plasma prostaglandin I2 (6-keto-prostaglandin F1 alpha) prostaglandin E2, and thromboxane B2 levels in pregnant women were unaffected by angiotensin II infusions. Neither changes in angiotensin II metabolism nor angiotensin II-induced increases in plasma levels of prostaglandin I2, prostaglandin E2, or the prostaglandin I2/thromboxane A2 ratio appear responsible for the decreased pressor response sensitivity to infused angiotensin II observed during normal human pregnancy.

Prevaccination with diluted freund adjuvant prevents the development of chronic pain and transient release of cerebrospinal fluid substance P in adjuvant-induced arthritis in rats

Parallel time courses of preclinical and behavioural pain-related parameters and levels of substance P-like immunoreactivity in plasma (plasma-SPLI) and cerebrospinal fluid (CSF-SPLI) were studied in 2 groups of rats injected with an arthritogenic solution (concentrated Freund adjuvant) over a 9-week post-infection (PI) period; 1 group was pretreated with saline (control) and 1 pretreated with diluted Freund adjuvant (immunized). In control rats all symptoms of adjuvant-induced arthritis (AIA) developed while in immunized rats AIA symptoms were significantly reduced or did not appear. A significant increase in plasma-SPLI was obvious as early as the 2nd week PI and remained at this level in both groups of animals until the end of the 9-week PI observation period, but with a significantly higher increase in control versus immunized group at all stages. In contrast, CSF-SPLI transiently peaked only in the control group at 3 weeks PI whereas CSF-SPLI values did not differ from one week to another in both groups of rats. These results suggest that successive injections of diluted Freund adjuvant impairs the development of chronic inflammation and pain in AIA in rats, as well as the transient increase in SP release in CSF at 3 weeks PI, but not the long-lasting increased SP release in plasma. Since there is a clear dissociation between our biochemical and preclinical and behavioral data, this study does not provide evidence for the role of substance P as a possible biologic marker of chronic pain either in plasma or in CSF. This study questions the use of SP measurements as a biological marker of chronic pain.

The effect of a single intraperitoneal dose of hrIL-1α on substance P-, neurokinin A-, calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity in cerebrospinal fluid, plasma and knee joint synovial fluid in the rat

Substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivity (-LI) was studied in rats' cerebrospinal fluid (CSF), plasma and synovial fluid (SF) from both knee joints at 2 and 24 h following an intraperitoneal administration of 0.05 ml human recombinant interleukin-1α (i.p. hrIL-1α) or saline. Increased or decreased levels of SP-, NKA and CGRP-LI were detected in CSF and plasma, whereas NPY-LI was unaffected. In SF only CGRP-LI increased bilaterally. There was a correlation in CGRP-LI content between plasma and CSF following i.p. hrIL-1α but not between plasma and SF or CSF and SF. It can be concluded that (1) i.p. hrIL-1α activates somatosensory afferents thereby increasing SP- and CGRP-LI content in CSF and plasma and NKA-LI in CSF; 2) i.p. hrIL-1α induces a bilateral increase of CGRP-LI in SF which is not mediated through systemic circulation and is possibly a part of the general host defensive reaction.

Changes of endothelin concentration in cerebrospinal fluid and plasma of patients with aneurysmal subarachnoid hemorrhage

To investigate the clinical significance of endothelin (ET), a potent vasoconstrictor peptide, in subarachnoid hemorrhage (SAH) and SAH-related cerebral vasospasm, we measured the ET-like immunoreactivity (ET-LI) in plasma and cerebrospinal fluid (CSF) obtained serially from patients with SAH due to ruptured cerebral aneurysm who underwent aneurysmal surgery. The normal ET-LI levels in plasma and CSF (n = 24) were 12.4 +/- 2.0 (mean +/- s.d.) and 9.1 +/- 1.2 pg.ml-1, respectively. Plasma ET-LI levels in patients with SAH before surgery (16.8 +/- 7.8 pg.ml-1, n = 8) were higher than the normal values (P < 0.05), and became further elevated after surgery (22.5 +/- 9.4 pg.ml-1). ET-LI levels in plasma and CSF one day after surgery were 18.7 +/- 5.5 and 18.4 +/- 6.8 pg.ml-1 (P < 0.01 vs. normal values), respectively, and declined thereafter. The plasma and CSF ET-LI levels in patients who showed symptomatic vasospasm became concomitantly elevated again. These results suggest that ET is involved in SAH-related vasospasm and raise the possibility that surgical stress influences the vasospasm.