Role of the neutral endopeptidase 24.11 in the conversion of big endothelins in guinea-pig lung parenchyma

1. We have studied the conversion of big endothelin-1 (big ET-1), big endothelin-2 (big ET-2) and big endothelin-3 (big ET-3) and characterized the enzyme involved in the conversion of the three peptides in guinea-pig lung parenchyma (GPLP). 2. Endothelin-1 (ET-1), endothelin-2 (ET-2) and endothelin-3 (ET-3) (10 nM to 100 nM) caused similar concentration-dependent contractions of strips of GPLP. 3. Big ET-1 and big ET-2 also elicited concentration-dependent contractions of GPLP strips. In contrast, big ET-3, up to a concentration of 100 nM, failed to induce a contraction of the GPLP. 4. Incubation of strips of GPLP with the dual endothelin converting enzyme (ECE) and neutral endopeptidase (NEP) inhibitor, phosphoramidon (10 microM), as well as two other NEP inhibitors thiorphan (10 microM) or SQ 28,603 (10 microM) decreased by 43% (P < 0.05), 42% (P < 0.05) and 40% (P < 0.05) the contractions induced by 30 nM of big ET-1 respectively. Captopril (10 microM), an angiotensin-converting enzyme inhibitor, had no effect on the contractions induced by big ET-1. 5. The incubation of strips of GPLP with phosphoramidon (10 microM), thiorphan (10 microM) or SQ 28,603 (10 microM) also decreased by 74% (P < 0.05), 34% and 50% (P < 0.05) the contractions induced by 30 nM big ET-2 respectively. As for the contractions induced by big ET-1, captopril (10 microM) had no effect on the concentration-dependent contractions induced by big ET-2. 6. Phosphoramidon (10 microM), thiorphan (10 microM) and SQ 28,603 (10 microM) significantly potentiated the contractions of strips of GPLP induced by both ET-1 (30 nM) and ET-3 (30 nM). However, the enzymatic inhibitors did not significantly affect the contractions induced by ET-2 (30 nM) in this tissue. 7. These results suggest that the effects of big ET-1 and big ET-2 result from the conversion to ET-1 and ET-2 by at least one enzyme sensitive to phosphoramidon, thiorphan and SQ 28,603. This enzyme corresponds possibly to EC 3.4.24.11 (NEP 24.11) and could also be responsible for the degradation of ETs in the GPLP.

Peripheral blood flow responses to exercise after successful correction of coarctation of the aorta

OBJECTIVES

The purpose of this study was to characterize peripheral flow kinetics in response to progressive discontinuous maximal exercise in 10 patients who underwent repair of coarctation of the aorta and 11 age-matched healthy adolescents.

BACKGROUND

An impairment of leg blood flow has been suggested on the basis of exaggerated femoral muscle lactate accumulation in patients with successful repair of coarctation. Few data are available describing blood flow kinetics of the exercising leg in such patients.

METHODS

Duplex ultrasound provided transcutaneous measurements of peak systolic and end-diastolic flow velocities of the femoral, humeral and renal arteries at rest and immediately after mild, moderate and maximal exercise intensities for computation of mean velocity, resistance index and femoral blood flow.

RESULTS

Femoral mean velocity and femoral blood flow increased linearly with exercise intensity in both groups, but the slope of this increase was significantly lower in patients. Similarly, humeral mean velocity increased significantly less in patients than in control subjects. Femoral resistance index sharply decreased from that at rest (patients [mean +/- SE] 1.4 +/- 0.04; control subjects 1.4 +/- 0.03) to mild exercise intensity in both groups (patients 0.69 +/- 0.03; control subjects 0.72 +/- 0.03). A further decrease was observed at maximal exercise in patients (0.60 +/- 0.04, p = 0.08) but not in control subjects (0.69 +/- 0.02).

CONCLUSIONS

These observations suggest that despite a greater exercise-induced femoral vasodilation, patients with successful correction of coarctation of the aorta demonstrate an impaired lower limb blood flow in response to strenuous dynamic exercise. In the absence of stenosis at rest, this alteration could result from exaggerated flow turbulence in the descending aorta distal to the site of correction because of loss of elasticity at the site of the resection of the coarcted segment.

[Hypertension and pregnancy. Diagnosis, physiopathology and treatment]

This review on hypertension in pregnancy focuses mainly on the pathophysiology and prevention of pregnancy induced hypertension which, when associated with proteinuria, is usually called preeclampsia. Rather than a genuine hypertensive disease, preeclampsia is mainly a systemic endothelial disease causing activation of platelets and diffuse ischemic disorders whose most obvious clinical manifestations involve the kidney (hence the proteinuria, edema and hyperuricemia), the liver (hence the hemolytic elevated liver enzymes and low platelets, or HELLP syndrome), and the brain (hence eclamptic convulsions). Hypertension is explained by increased vascular reactivity rather than by an imbalance between vasoconstrictive and vasodilating circulating hormones. This increased reactivity is due to endothelial dysfunction with imbalance between prostacyclin and thromboxane A2 and possibly dysfunction of NO and endothelin synthesis. The aggressive substances for endothelium are thought to be of placentar origin and the cause of their release is explained by placentar ischemia related to a defect of trophoblastic invasion of the spiral arteries. The etiology of this latter defect is unknown but involves immunologic mechanisms with genetic predisposition. The only effective treatment for PIH is extraction of the baby with the whole placenta. The decision for extraction is often a very delicate obstetric problem. Antihypertensive drugs are mainly indicated in severe hypertension (> 160-100 mm Hg), with the aim of preventing cerebral hemorrhage in the mother, but have not been shown to improve fetal morbidity or mortality. Eclamptic seizures can be prevented and treated more effectively with magnesium sulfate than with diazepam or phenytoin. Prevention of preeclampsia remains the main challenge. Whereas antihypertensive drugs are ineffective, calcium supplementation and low dose aspirin have proven effective but mainly in selected populations with a relatively high incidence of preeclampsia (> 8-10%). In multiparas the selection of such a high risk population is relatively easy when at least 2 (or 1?) previous pregnancies were complicated with early preeclampsia and/or intrauterine growth retardation. In nulliparas the selection of the high-risk population is still a subject of research. The 2 most promising criteria are abnormal Doppler velocimetry of the uterine arteries at around 20 weeks of amenorrhea, and abnormally high plasma levels of beta HCG at 17 weeks of amenorrhea.

Effect of docosahexaenoic acid and eicosapentaenoic acid in the phospholipids of rat heart muscle cells on adrenoceptor responsiveness and mechanism

The specific effect of docosahexaenoic (DHA; C22:6 n-3), as compared to eicosapentaenoic acid (EPA; C20:5 n-3), on adrenoceptor function was investigated in cultured rat myocardial cells. The cardiomyocytes were grown for 24 h in a conventional seric medium, and then incubated for 96 h in a medium enriched with either DHA or EPA. After this treatment, the phospholipids of the DHA-treated cells contained approximately 20% of the total fatty acids as C22:6 n-3, and those of EPA-treated cells displayed a high content in C20:5 n-3 and its elongation product C22:5 n-3 (30% of total fatty acids). Additionally, the n-3/n-6 polyunsaturated fatty acid ratio was the same in the two groups of cells. These modifications were roughly similar in all the phospholipid classes. The contractions were monitored photometrically and no significant difference in basal frequency and contraction parameters could be detected. The stimulation of the beta-adrenergic receptors (isoproterenol 10(-7) M) resulted in a positive chronotropic effect, which was significantly higher in the DHA-rich cells. Conversely, the higher DHA content in the phospholipids appeared to induce a decrease in the affinity of the beta-receptors for the ligand (dihydroalprenolol) without alteration of the number of beta-receptor binding sites and provoked a significant decrease in isoproterenol-stimulated cAMP production (-19%). To investigate further these controversial data, the cardiomyocytes were treated with dibutyryl-cAMP, which elicited a positive chronotropic response significantly higher in the DHA-rich cells. The alpha-adrenergic stimulation by phenylephrine (3 x 10(-6) M) increased the spontaneous rate, but in a similar manner in the DHA- and EPA-enriched cells. Similarly, neither the alpha-adrenergic receptor binding characteristics nor the production of phosphoinositides was modulated by the membrane DNA content, although the phosphatidylinositol PUFAs were significantly altered. In conclusion, increasing the DHA content in membrane phospholipids did not affect the alpha-adrenergic system, but exerted a specific positive influence on the beta-adrenergic transduction mechanism, essentially through an increase of cAMP efficiency.

Characterization of a binding site for angiotensin IV on bovine aortic endothelial cells

We have characterized a specific binding site for angiotensin IV on bovine aortic endothelial cell membranes. Pseudo-equilibrium studies at 37 degrees C for 2 h have shown that this binding site recognizes angiotensin IV with a high affinity (Kd = 0.71; average of two experiments that yielded values of 0.71 and 0.72 nM). The binding site is saturable and relatively abundant with a maximal binding capacity of 0.59 pmol/mg protein (average of two experiments that yielded values of 0.39 and 0.78 pmol/mg of protein). Non-equilibrium kinetic analyses at 37 degree C revealed a calculated Kd of 59 pM (average of two experiments that yielded values of 67 and 50 pM). The binding site displays a high affinity for angiotensin receptors AT1 or AT2. An analysis of specificity showed that the binding site displays a high affinity for angiotensin IV, low affinities for angiotensin II, [Sar1, Val5, Ala8]angiotensin II and does not recognize L-158,809 (5,7-dimethyl-2-ethyl-3-[(2'-(1 H-tetrazole-5-yl)[1,1'-biphenyl]-4-yl)methyl]-3H-imidazo[4, 5-beta]pyridine H2O) and PD 123319 (1-[4-dimethylamino)3-methylphenyl]methyl-5-(diphenylacetyl) 4,5,6,7-tetrahydro-1 H-imidazo[4,5-c]pyridine-6-carboxylic acid). A few unrelated hormones (bradykinin, [Arg8] vasopressin, endothelin-1, atrial natriuretic factor, isoproterenol and adrenocorticotropic hormone) were unable to inhibit any 125I-angiotensin IV binding. The affinities of different structural analogues of angiotensin IV revealed that the N-terminal position is critical for receptor recognition and the C-terminal proline is also important. GTP gamma S and polyvinyl sulfate did not affect the binding, suggesting that the receptor is not coupled to a G-protein. The divalent cations Mg2+ and Ca2+ were shown to diminish the binding of 125I-angiotensin IV. Cross-linking of 125I-angiotensin IV to bovine aortic endothelial cell membranes in the presence of disuccinimidyl suberate, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a major band of 186 +/- 12 kDa. The presence in high concentration of this angiotensin binding site on aortic endothelial cells suggest the existence of a novel mechanism involved in the control of vascular tone or vascular permeability.

Characterization of endothelin receptors mediating mechanical responses to the endothelins in the isolated stomach strip of the rat

We have characterized the receptors mediating the mechanical responses of the isolated stomach strip to endothelin-1 (ET-1), endothelin-3 (ET-3) and the ETB-selective receptor agonists sarafotoxin 6c (SX6c) and IRL 1620. As antagonists we used BQ-123 (ETA receptor selective), BQ-788 (ETB receptor selective) and PD 145065 (ETA/ETB receptor nonselective). We have also compared the responses of the mature peptides to their precursors human big ET-1(1-38), porcine big ET-1(1-39) and big ET-3(1-41) amide. ET-1, ET-3, SX6c and IRL 1620 produced equipotent concentration-dependent contractions of the rat stomach strips that were antagonized by PD 145065 (10(-5) M) or BQ-788 (10(-5) M) but not by BQ-123 (10-5 M). This indicates that the ETB receptor mediates contractions to the endothelins in this preparation. In preparations precontracted with PGE2 (3 x 10(-8) M), ET-1, but not SX6c (both 3 x 10(-9) M), caused a transient (< 2 min) relaxation (approx. 40% of the induced tone). This relaxation was antagonized by BQ-123 (10(-5) M) but prolonged by BQ-788, and therefore mediated by ETA receptors. A single administration of 3 x 10(-7) M ET-1, ET-3, SX6c or IRL 1620 produced contractions that reached a maximal response after 1 to 3 min. The contractions were not maintained, although responses to ET-1 or ET-3 lost their tone less rapidly than those to SX6c or IRL 1620.(ABSTRACT TRUNCATED AT 250 WORDS)

[Arteriovenous and arterial-digestive system fistulas complicating isolated iliac aneurysm]

Isolated iliac aneurysms are often discovered when they rupture, sometimes into a neighbouring organ. We report 2 cases of aneurysm of the common iliac artery, one which ruptured into the right common iliac vein and the other in to the sigmoid. Diagnosis was made at laparotomy in the first case and on the CT-scan of the pelvis in the second. The first case was treated with an exclusion graft using ilio-iliac bypass with suture of the venous breach via the aneurysm. In the second case, the aneurysm was excluded by ligature of the iliac arteries with extra-anatomic crossed femoro-femoral bypass, sigmoid colostomy and drainage of the pelvis. These two cases illustrate the importance of digital examination of the pelvis and CT-scan for the diagnosis of complicated aneurysms of the iliac vessels. Rapid surgery is a determining factor in prognosis.

A high selectivity cascade filtration technique for LDL-cholesterol and Lp(a) removal

This work proposes an improvement of the cascade filtration technique in the treatment of familial hypercholesterolemia. A model of the whole process permitted the definition of the parameters that could influence the selectivity of the fractionation: the pore size, the sieving coefficients of both fractionation and plasmapheresis membrane, and the final retentate flow rate. In vivo studies have shown that the dead-end mode for the secondary filter was not always practical because of severe membrane plugging except when a pulsatile pump was included in the extracorporeal circuit. This pump generated hydrodynamic instabilities which decreased membrane fouling and retarded the build up of the polarization concentration layer. Optimization of these specific operating conditions permitted increase in the selectivity index from 1.15 to 2.24. The performances of cascade filtration were then comparable to those of adsorption on dextran sulfate columns.

Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates adenylyl cyclase and phospholipase C activity in rat cerebellar neuroblasts

The presence of receptors for the novel neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been recently demonstrated in the external granule cell layer of the cerebellum, a germinative matrix that generates the majority of cerebellar interneurons. In the present study, we have taken advantage of the possibility of obtaining a culture preparation that is greatly enriched in immature cerebellar granule cells to investigate the effect of PACAP on the adenylyl cyclase and phospholipase C transduction pathways. The two molecular forms of PACAP, i.e., 27-(PACAP27) and 38-(PACAP38) amino-acid forms of PACAP, induced a dose-dependent stimulation of cyclic AMP production in granule cells. The potencies of PACAP27 and PACAP38 were similar (ED50 = 0.12 +/- 0.01 and 0.23 +/- 0.07 nM, respectively), whereas vasoactive intestinal polypeptide (VIP) was approximately 100 times less potent. PACAP27 and PACAP38 also induced a dose-dependent stimulation of polyphosphoinositide breakdown (ED50 = 19.1 +/- 6.3 and 13.4 +/- 6.0 nM, respectively), whereas VIP had no effect on polyphosphoinositide metabolism. The effect of PACAP38 on inositol phosphate formation was significantly reduced by U-73122 and by pertussis toxin, indicating that activation of PACAP receptors causes stimulation of a phospholipase C through a pertussis toxin-sensitive G protein. In contrast, forskolin and dibutyryl cyclic AMP did not affect PACAP-induced stimulation of inositol phosphates. Taken together, the present results demonstrate that PACAP stimulates independently the adenylyl cyclase and the phospholipase C transduction pathways in immature cerebellar granule cells. These data favor the concept that PACAP may play important roles in the control of proliferation and/or differentiation of cerebellar neuroblasts.

Effects of the ETA/ETB receptor antagonist, bosentan on endothelin-1-induced myocardial ischaemia and oedema in the rat

1. The purpose of this study were to assess the role of ETB receptors in mediating endothelin-1 (ET-1)-induced myocardial ischaemia and oedema in rats and to study the inhibitory action of the novel nonpeptide ETA/ETB receptor antagonist, bosentan on these actions of ET-1. 2. Intravenous bolus injection of ET-1 (1 nmol kg-1) into anaesthetized rats produced marked ST segment elevation of the electrocardiogram without causing arrhythmias. ST segment elevation developed within 30-50 s and persisted for at least 30 min following injection of the peptide. 3. Pretreatment of the animals with bosentan (10 mg kg-1, i.v.) inhibited on average by 96% the ST segment elevation elicited by ET-1 (1 nmol kg-1) compared to the 82% inhibition observed with the ETA receptor-selective antagonist, FR 139317 (2.5 mg kg-1, i.v.). 4. Bolus injection of ET-1 (1 nmol kg-1, i.v.) to conscious chronically catheterized rats evoked a transient depressor response followed by a prolonged pressor effect. Corresponding to changes in blood pressure, a transient tachycardia and a sustained bradycardia were observed. ET-1 (1 nmol kg-1) enhanced albumin extravasation by 119 and 93% in the left ventricle and right atrium, respectively, as measured by the local extravascular accumulation of Evans blue dye. 5. Pretreatment of the animals with bosentan (10 mg kg-1) inhibited by 71 and 90% the depressor and pressor actions of ET-1 (1 nmol kg-1) and the accompanying tachycardia and bradycardia, respectively. FR 139317 (2.5 mg kg-1) attenuated the pressor response to ET-1 and accompanying bradycardia by 75%, without affecting the depressor action and accompanying tachycardia. ET-1-induced albumin extravasation was completely inhibited by bosentan (10 mg kg-1) both in the left ventricle and right atrium, compared to the 86% inhibition observed with FR 139317 (2.5 mg kg-1).6. Like ET-1, the ETB receptor-selective agonist, IRL 1620 (0.3 and 1 nmol kg-1, i.v.) also produced dose-dependent ST segment elevation in anaesthetized rats and enhanced albumin extravasation (up to141% of control) in the left ventricle and right atrium, respectively, in conscious rats. These effects ofIRL 1620 were completely prevented by bosentan (10 mg kg-1).7. These results indicate that ETB receptors, albeit to a lesser extent than ETA receptors, are also involved in mediating ET-1-induced myocardial ischaemia and oedema in the rat, and suggest the therapeutic potential for bosentan in the treatment of ischaemic myocardial diseases.

Effect of centrally administered neuropeptide Y on hypothalamic and hypophyseal proopiomelanocortin-derived peptides in the rat

In a previous study, we have shown that neuropeptide Y inhibits the release of alpha-melanocyte-stimulating hormone from the rat hypothalamus in vitro. The aim of the present study was to investigate the possible effect of neuropeptide Y on the regulation of proopiomelanocortin-derived peptides in vivo. Rats received acute or chronic administration of neuropeptide Y in the lateral ventricle and the amount of alpha-melanocyte-stimulating hormone was measured in the hypothalamus and in the neurointermediate lobe of the pituitary. In the same experiments, the amounts of corticotropin-releasing factor and corticotropin were quantified in the hypothalamus and anterior pituitary, respectively. Acute treatment with synthetic neuropeptide Y (0.1 to 10 micrograms/rat) did not modify the amount of alpha-melanocyte-stimulating hormone in the hypothalamus. In contrast, chronic infusion of neuropeptide Y (1.25 micrograms/h) over a seven day period significantly decreased the hypothalamic content of alpha-melanocyte-stimulating hormone, suggesting that neuropeptide Y regulates the synthesis and/or the processing of proopiomelanocortin. Concurrently, we found that both acute and chronic infusion of neuropeptide Y induced a significant reduction in corticotropin-releasing factor in the hypothalamus as well as a significant decrease in alpha-melanocyte-stimulating hormone and corticotropin in the neurointermediate and anterior lobes, respectively. Quantitative in situ hybridization histochemistry showed that chronic administration of neuropeptide Y also caused a reduction of proopiomelanocortin messenger RNA levels both in the intermediate and anterior lobes of the pituitary. Administration of neuropeptide Y (10(-6) M) on perifused rat hypothalamic slices caused a significant increase in corticotropin-releasing factor release.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization trial of cats with a replication-defective adenovirus type 5 expressing the ENV gene of feline immunodeficiency virus

Our aim was to develop a recombinant replication-defective adenovirus suitable for the vaccination of cats against feline immunodeficiency virus. We first demonstrated that this vector was able to transfer a marker gene (E. coli beta-galactosidase) in feline cells in vitro. We then constructed an adenovirus type 5 expressing the Feline Immunodeficiency Virus (FIV) envelope (ENV) gene of the Wo isolate in the absence of the rev gene (Ad-ENV-Wo). Ad-ENV-Wo was then tested in four cats in a 3 injections scheme (at day 0, day 30 and day 210). Four other control cats received Ad-gp50, a similar recombinant adenovirus expressing gp50 (Ad-gp50) of pseudorabies virus (PRV). Viruses were formulated in two different kind of oil adjuvants (water/oil and water/oil/water), a protocol previously shown to enhance the immune response against the virus-induced protein. The control cats developed neutralizing antibodies against PRV, demonstrating the potency of recombinant human adenovirus 5 (Ad5) as a vector in cats. Antibody responses appeared after the first injection and were higher with the water/oil/water formulation than with the water/oil controls. However, none of the four cats vaccinated with Ad-ENV-Wo developed antibodies against two peptides of the envelope protein. Animals were challenged with 20 infectious doses 50% of the strain Wo. All of them developed antibodies against FIV within 4 to 5 weeks, and FIV virus could be isolated from all.

Structure of human calcitonin gene-related peptide (hCGRP) and of its antagonist hCGRP 8-37 as determined by NMR and molecular modeling

The solution structures of human calcitonin gene-related peptide (hCGRP, 37 residues) and of its antagonistic fragment hCGRP 8-37 have been determined by two-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. Analysis of the double quantum filtered correlation spectroscopy, total correlation spectroscopy and nuclear Overhauser enhancement spectroscopy spectra led to a complete assignment and to the identification of more than 350 intra- and interresidue connectivities for each peptide. Molecular models were calculated by molecular dynamics and energy minimization using distance constraints. The structure of hCGRP is characterized by a rigid N-terminal disulfide-bonded loop followed by helix segments (Val8-Leu16), a gamma-turn (Ser19-Gly21) and several local hydrogen-bonded patterns. The structure of hCGRP 8-37 is less defined than the structure of hCGRP and no helix structure is present. Molecular models of both peptides are consistent with the NH temperature coefficients and secondary chemical shifts of the alpha-protons. Hydrogen bonding with the disulfide-bonded ring appears to be critical for helix formation, both structural elements being essential for agonistic activity.

Frog vasoactive intestinal polypeptide and galanin: primary structures and effects on pituitary adenylate cyclase

Vasoactive intestinal polypeptide (VIP) and galanin were isolated in pure form from the stomach of the European green frog, Rana ridibunda. Frog VIP is identical to the previously characterized VIP from chicken and alligator. The primary structure of frog galanin contains only two amino acid substitutions (asparagine for histidine at position 23 and histidine for tyrosine at position 26) compared with porcine galanin. The data indicate that evolutionary pressure to conserve the amino acid sequence of both peptides during the evolution of amphibia to mammals has been strong. Synthetic frog VIP produced a dose-dependent increase in cAMP concentration in frog anterior pituitary fragments. The potency of the peptide (ED50 = 1.2 x 10(-6) M; mean +/- SE; n = 8) was comparable to that of porcine VIP (EC50 = 1.3 x 10(-6) M), but was approximately 10-fold less than that of frog pituitary adenylate cyclase-activating polypeptide [PACAP-(1-38); ED50 = 1.1 x 10(-7) M] in the same system. The increases in cAMP concentrations produced by maximal doses of PACAP (10(-5) M) and VIP (10(-5) M) were not additive. The data suggest that the effects of both peptides are mediated through a common PACAP-preferring receptor that is pharmacologically different from the mammalian PACAP type I receptor. Synthetic frog galanin also produced a dose-dependent increase in the concentration of cAMP in isolated frog anterior pituitary fragments (ED50 = 9.3 x 10(-8) M) consistent with a possible role for the peptide as a hypophysiotropic factor in amphibians.

Neuropeptide tyrosine in the brain of the African lungfish, Protopterus annectens: immunohistochemical localization and biochemical characterization

Lungfishes, which share similarities with both fishes and amphibians, represent an interesting group in which to investigate the evolutionary transition from fishes to tetrapods. In the present study, we have investigated the localization and biochemical characteristics of neuropeptide Y (NPY)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. NPY-immunoreactive cell bodies were found in various regions of the brain, most notably in the telencephalon (septal area, ventral striatum, and nucleus accumbens), in the diencephalon (preoptic nucleus, periventricular region of the hypothalamus, and ventral thalamus), and in the tegmentum of the mesencephalon. A strong immunoreaction was also detected in cell bodies of the nervus terminalis. Immunoreactive nerve fibers were particularly abundant in the ventral striatum, the nucleus accumbens, the diagonal band of Broca, the hypothalamus, and the mesencephalic tegmentum. Positive fibers were also seen in the median eminence and in the neural lobe of the pituitary. The NPY-immunoreactive material localized in the brain and pituitary was characterized by combining high-performance liquid chromatography (HPLC) analysis and radioimmunological quantitation. The displacement curves obtained with synthetic porcine and frog NPY and serial dilutions of brain and pituitary extracts were parallel. Reversed-phase HPLC analysis of telencephalon, diencephalon, and pituitary extracts resolved a major NPY-immunoreactive peak that coeluted with frog NPY. The similarity between the distribution of NPY-containing neurons and the biochemical characteristics of the immunoreactive peptide in the brain of lungfish and frog strongly favors a close phylogenetic relationship between dipnoans and amphibians.

Involvement of the Y2 receptor subtype in the regulation of prolactin gene expression by neuropeptide Y in the male rat

In order to determine the influence of neuropeptide Y (NPY) on the biosynthesis of prolactin (PRL), we have studied the effects of NPY and some NPY analogs on PRL gene expression in the male rat anterior pituitary gland. The following peptides (4 micrograms/100 g body wt): NPY, peptide YY (PYY), NPY13-36 (a Y2 receptor agonist) and [Leu31,Pro34]NPY (a Y1 receptor agonist) were injected into the left lateral ventricle of adult male rats. Control animals received only the vehicle (0.9% NaCl). All the animals were perfused with 4% paraformaldehyde 4 h after injection and processed for in situ hybridization. The intracerebroventricular injection of NPY, PYY, and NPY13-36 induced a significant increase in the hybridization signal (22-40% over control). On the other hand, the Y1 receptor agonist [Leu31,Pro34]NPY did not influence PRL mRNA levels. These data then suggest that activation of the Y2 NPY receptor subtype at the central level can positively regulate PRL gene expression.

Acute pro-inflammatory actions of endothelin-1 in the guinea-pig lung: involvement of ETA and ETB receptors

1. Although recent observations suggest that endothelin-1 (ET-1) may play a role in the pathogenesis of asthma, to date little is known about the effects of ET-1 on parameters other than bronchoconstriction. The objectives of the present experiments were to study whether intravenously administered ET-1 could exert pro-inflammatory actions in the guinea-pig lung and to assess the involvement of endothelin ETA and ETB receptors in these events by using the ETA receptor-selective antagonist, FR 139317, the novel ETA/ETB receptor antagonist, bosentan and the ETB receptor-selective agonist, IRL 1620. 2. Bolus i.v. injection of ET-1 (0.1-1 nmol kg-1) to anaesthetized guinea-pigs evoked dose-dependent increases in mean arterial blood pressure which lasted for 6-12 min. This was accompanied by a dose-dependent haemoconcentration (8-15% plasma volume losses) and increases (up to 546%) in albumin extravasation in the trachea, upper and lower bronchi, but not in the pulmonary parenchyma. Qualitatively similar changes were observed following i.v. injection of the ETB receptor agonist, IRL 1620 (0.3 and 1 nmol kg-1), although IRL 1620 appeared to be about 3 times less potent than ET-1. The ETA receptor-selective antagonist, FR 139317 (2.5 mg kg-1) inhibited the ET-1 (1 nmol kg-1)-induced pressor response, haemoconcentration and albumin extravasation by 75, 77 and 60-70%, respectively, whereas it did not attenuate IRL 1620 (1 nmol kg-1)-induced changes. The ETA/ETB receptor antagonist, bosentan (10 mg kg-1) almost completely inhibited the pressor, haemoconcentration and permeability effects of both ET-1 and IRL 1620. 3. ET-1, but not IRL 1620 (0.1-1 nmol kg-1), produced a dose-dependent neutropenia with relative lymphocytosis and monocytosis, but did not induce influx of neutrophil granulocytes into pulmonary tissues or the bronchoalveolar space. ET-1 (1 nmol kg-1)-induced neutropenia was prevented by pretreatment of the animals with FR 139317 (2.5 mg kg-1), bosentan (10 mg kg-1) or adrenaline (90 nmol kg-1), indicating that ET-1 caused intravascular sequestration of neutrophil granulocytes. 4. ET-1 or IRL 1620 (10(-10)-10(-6) M) alone did not activate alveolar macrophages in vitro, whereas at a concentration of 10(-8) M, ET-1, but not IRL 1620, markedly potentiated superoxide production in response to f-Met-Leu-Phe (10(-9)-10(-7) M) and platelet-activating factor (PAF, 10(-9)-10(-7) M), but not to phorbol 12-myristate 13-acetate (10(-9) M). ET-1 did not affect f-Met-Leu-Phe- or PAF-induced increases in intracellular free calcium concentration. This potentiating effect of ET-1 was abolished by FR 139317(1.5 X 10-7 M).5. We conclude that, in addition to evoking airway contractions, ET-1 exerts pro-inflammatory actions via activation of the ETA and to a lesser extent the ETB receptors, and therefore, might contribute to the airway inflammation present in asthma. These findings also suggest the therapeutic potential of ETA/ETB receptor and perhaps ETA receptor-selective antagonists in this disease.

Contractile activity of endothelin precursors in the isolated gallbladder of the guinea-pig: presence of an endothelin-converting enzyme

A single addition of 3 x I0-7 M ET-1, ET-2 or ET-3 produced contractions that reached a steady state in 28.2 +/- 4.2, 21.1 +/- 1.3 and 24.0 +/- 3.8 min, respectively and took 2.7 +/- 0.4, 2.1 + 0.1 and 1.6 +/- 0.1 min to reach half of this steady-state response.4. Contractions induced by 3 x I0-7 M big ET-11-38 or big ET-11- 39 reached a plateau in 38.5 +/- 3.6 and 35.6 +/- 3.3 min, respectively, and half of these responses were attained in 12.0 +/- 2.5 and 7.1 +/- 1.1 min.Thus, these contractions developed more slowly than those induced by ET-1. Contractions induced by 3 x 10-7 M big ET-21-38 were also much slower to develop than those to ET-2, for these took 49 +/- 2 min to reach plateau and 19.4 +/- 2.1 min to attain half that response. Contractions induced by 3 x 10-7 M big ET-31-41 amide took 50.2 +/- 3.7 min to reach a plateau and 27.3 +/- 3.0 min to reach half of this response.5. Phosphoramidon (0.1, 1 and 3 x 10-4 M) inhibited contractions induced by big ET-11.39. For instance,the contractions induced by 3 x 10-7 M big ET-11-39 were inhibited by 10-4 M or 3 x 10-4 M of phosphoramidon by 62.8 +/- 6.7% or 74.5 +/- 4.6%, respectively. Similarly, contractions induced by ET-21-38 were inhibited by 91.3 +/- 5.4% and the small response induced by big ET-3l-4l amide was abolished by 3 x 10-4M phosphoramidon. Conversely, the neutral endopeptidase (EC 24.11) inhibitor DL-thiorphan(3 x 10-4 M) had no effect. Captopril (10-5 M), pepstatin A (10-5 M), phenylmethylsulphonylfluoride(PMSF, 10-3 M), aprotinin (10-5 M), E-64 (10-5 M), cystatin (10-6 M), leupeptin (10-4 M),chymostatin (10-4 M), or bestatin (10-5 M) did not inhibit but rather increased to a similar, but small degree the contractions induced by 3 to 30 x 10-9 M big ET-11-39. Only captopril (10-5 M) or leupeptin(10-4 M) increased the contraction induced by 3 x 10-7 M big ET-11-39. Phosphoramidon (10-4 M),pepstatin (10-5 M) or PMSF (10-3 M) did not affect contractions induced by ET-1.6. Removal of the epithelium increased by 70% the size of the contraction induced by 5 microM histamine(1.08 +/- 0.05 g; n = 160 to 1.84 +/- 0.14 g; n = 12) but did not affect, in absolute terms, the contraction induced by ET-1 (as a % of the response to histamine, these responses were, of course, apparently depressed). Epithelium removal did, however, increase the size of the contractions induced by 3 to 30 x 10-9 M big ET-1 -39 which was very similar to the effect of the protease inhibitors.7. In competition binding studies on membranes prepared from the guinea-pig gallbladder, 10-11 MET-1 inhibited by 76.9 +/- 3.1% the binding of [125]-ET-I while porcine big ET-11-39 caused no inhibition(0.7 +/- 3.0; n = 3). ET-1 (10-6 M) inhibited binding by 95.7 =/- 1.1% (n = 3) while at this much higher concentration, big ET-11-39 inhibited binding by only 16.8 +/- 4.2% (n = 3). This clearly suggests that big ET-11-39 does not bind directly to ET receptors.8. Thus, a phosphoramidon-sensitive endothelin-converting enzyme (ECE), different from neutral endopeptidase (NEP; EC 24.11) and not located on the epithelium, converts big ET-1 into ET-1 in the gallbladder of the guinea-pig. This ECE appears to act preferentially on big ET-1 or big ET-2 over bigET-3.