Characterization of receptors mediating vascular responses to endothelin-1 in the conscious rat

1. The present study has determined the receptors mediating the vascular responses (pressor and depressor actions and vascular permeability effect) to endothelin-1 (ET-1) in the conscious rat by using the novel non-peptide ETA/ETB receptor antagonist, bosentan (Ro 47-0203, 4-tert-butyl-N-[6-(2 hydroxyethoxy)-5-(2-methoxy-phenoxy)-2,2'-bipyrimidine- 4-yl]benzene-sulphonamide), the ETA receptor-selective antagonist, FR 139317 and the ETB receptor-selective peptide agonist, IRL 1620. 2. Bolus injection of ET-1 (1 nmol kg-1, i.v.) resulted in a prolonged pressor effect (maximum increase in mean arterial blood pressure (MABP) was 47 +/- 3 mmHg, n = 6) preceded by a transient depressor response (maximum decrease in MABP was 17 +/- 1 mmHg). Both these responses were inhibited by bosentan (1-20 mg kg-1, i.v. bolus) in a dose-dependent manner. The maximum inhibition of ET-induced depressor and pressor responses did not exceed 53 and 87%, respectively. FR 139317 (2.5 mg kg-1, i.v.) attenuated the pressor response to ET-1 by 75% without affecting the depressor response. Furthermore, FR 139317, but not bosentan, prolonged the depressor action of ET-1. Corresponding to changes in blood pressure, a small transient tachycardia (delta heart rate 15 +/- 5 beats min-1) followed by a sustained bradycardia (delta heart rate -48 +/- 10 beats min-1, n = 6) was observed following injection of 1 nmol kg-1 ET-1. FR 139317 and bosentan (10 mg kg-1) inhibited ET-1-induced bradycardia by 79% and 71%, respectively.ET-l-induced tachycardia was significantly attenuated by bosentan,but not FR 139317.3. The ETB receptor agonist, IRL 1620 (0.1-2 micro molkg-1, i.v.) produced biphasic dose-dependent changes in MABP with an initial transient fall followed by a prolonged pressor action. The maximum decrease and increase in MABP were 11 +/- 2 and 19 +/- 3 mmHg, respectively (n = 5). These changes in MABP were accompanied by a transient tachycardia (Delta heart rate 9+/- 3 beats min-1) and prolonged bradycardia (Delta heart rate -17+/-11 beats min-1), respectively. Pretreatment of the animals with FR139317 (2.5 mg kg-1, i.v.) did not affect IRL 1620 (1 nmol kg-1)-induced changes in MABP and heart rate, whereas both the depressor and pressor actions of IRL 1620 and the accompanying tachycardia and bradycardia were almost completely inhibited by bosentan (10mgkg-1).4. ET-1 (1 nmol kg-1) enhanced albumin extravasation in the upper and lower bronchi, spleen, kidney,stomach and duodenum (up to 246%) as measured by the extravasation of Evans blue dye. FR 139317(2.5mgkg-1) completely inhibited ET-l-induced protein extravasation in the stomach and duodenum,whereas 40-75% inhibition was observed in the other vascular beds studied. The permeability effect of ET-l was almost completely inhibited by bosentan (10mgkg-1) in all vascular beds studied.5. IRL 1620 (0.4 or 1 nmol kg-1, i.v.) enhanced albumin extravasation (up to 219%) in the upper and lower bronchi, spleen and kidney in a dose-dependent manner. Unlike ET-1, IRL 1620 failed to increase albumin extravasation in the stomach and duodenum.6. The present study demonstrates in the conscious rat that ETA and ETB receptors are responsible for mediating the majority of the pressor response to ET-l and suggest that a small component of the ET-l pressor response might be mediated via a non-ETA, non-ETB receptor, whereas ETB and perhaps a non-ETA, non-ETB receptor may mediate the depressor action of ET-1. Furthermore, the ET-1 induced albumin extravasation is mediated solely via ETA receptors in the stomach and duodenum, whereas both ETA and ETB receptors are involved in the permeability effect of ET-l in the bronchial, splenic and renal vascular beds.

Neurochemical effects of neuropeptide Y (NPY) and NPY2-36

Our previous in vivo structure-activity studies suggested that the putative receptors mediating the effects of NPY and NPY2-36 on food intake and body temperature following ICV administration are pharmacologically different. In the present study, we examined and compared dose related effects of NPY and NPY2-36 on levels of norepinephrine (NE), dopamine (DA) and its main metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA), as well as serotonin (5-HT) and its metabolite, 5-hydroxyindolacetic acid (5-HIAA), in several brain regions of the rat, including: frontal cortex, hypothalamus, amygdala, septum, nucleus accumbens, corpus striatum, globus pallidus, substantia nigra and hippocampus. NPY and NPY2-36 (10 or 20 micrograms) were administered intraventricularly and the regional levels of the amines and metabolites were assessed 30 min following administration. Results indicate that both doses of NPY decreased NE levels within the hypothalamus. Furthermore, DOPAC concentrations were increased in this region while DA and HVA remained unchanged. The most pronounced neurochemical effects of NPY were found in the hippocampus, where the peptide produced dose related increases in DA, DOPAC and HVA. On the other hand, NPY2-36 significantly increased NE, DA and its metabolite DOPAC in both the amygdala and septum. The metabolism of DA was most obviously affected in the hippocampus and frontal cortex where levels of DA and DOPAC were significantly increased. 5-HT was affected in both the hypothalamus and globus pallidus where DA and its metabolite HVA were also increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of pituitary adenylate cyclase-activating polypeptide (PACAP) receptors in the rat cerebellum: a quantitative autoradiographic study

Pituitary adenylate cyclase-activating polypeptide and PACAP receptors are both present in the rat cerebellar cortex, suggesting that PACAP may play an important role in the cerebellum. In the present study, the variation of the concentration of PACAP binding sites in the rat cerebellum was investigated during postnatal development by means of quantitative autoradiography, using [125I]PACAP27 as a radioligand. In the external granule cell layer and the medulla, the density of PACAP binding sites was high at birth, markedly decreased from postnatal day 8 (P8) to P25 and finally vanished at the end of the third postnatal week. In the internal granule cell layer and molecular layer, PACAP binding sites were first detected at P8. In the internal granule cell layer, the density of binding sites slightly decreased during development but remained elevated in adults. Conversely, in the molecular layer, PACAP binding sites rapidly decreased during the second and third postnatal weeks and virtually disappeared after P25. In all four layers of the cerebellar cortex, the autoradiographic labeling was displaced by PACAP27 (IC50 close to 10(-8) M), but was not affected by VIP. No significant changes in IC50 and Hill coefficient were noticed in the various layers throughout development. The present study shows that all four layers of the cerebellar cortex express PACAP binding sites during development. The evolution of the receptor concentration exhibited differential profiles in the various layers but the specificity characteristics of the recognition sites were identical in all four structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of neuropeptide Y in the regulation of gonadotropin-releasing hormone gene expression in the rat preoptic area

It is well documented that neuropeptide Y (NPY) is involved in the regulation of the hypothalamo-pituitary gonadal axis. In order to determine the influence of NPY on the biosynthesis of GnRH, we have studied the effects of NPY and some NPY analogs on GnRH gene expression in neurons in the male rat preoptic area (POA). The following peptides NPY, peptide YY (PYY), [Leu31,Pro34]NPY (a Y1 receptor agonist) and NPY13-36 (a Y2 receptor agonist) were injected into the left lateral ventricle of adult castrated male rats. In another series of experiments, the same peptides were administered intravenously (IV). All the animals were perfused with 4% paraformaldehyde 4 hours after injection. Cryostat sections through the POA were processed for quantitative in situ hybridization. The intracerebroventricular injection of PYY, NPY and [Leu31,Pro34]NPY induced a marked increase in the number of grains overlying the labelled neurons (20 to 45% over control). On the other hand, the Y2 receptor agonist NPY13-36 did not influence mRNA levels. Similar results were obtained following the i.v. administration although the magnitude of the stimulating effect was less important (12 to 20% over control). These data then strongly suggest that NPY positively regulates the genetic expression of GnRH in neurons via the Y1 NPY receptor subtype.

Peptide YY derivatives as selective neuropeptide Y/peptide YY Y1 and Y2 agonists devoided of activity for the Y3 receptor sub-type

Peptide YY derivatives were evaluated for their respective ability to bind and activate the NPY/PYY receptor sub-types (Y1, Y2 and Y3) present in various preparations. The analogue [Leu31,Pro34]PYY demonstrated high (nM) affinity in rat frontoparietal cortical membrane preparations (Y1-enriched tissue) and the rabbit saphenous vein (Y1 in vitro bioassay) but only low affinity in a Y2-enriched preparation (rat hippocampus). In contrast, PYY C-terminal fragments such as PYY3-36 and PYY13-36 were more potent in Y2 than Y1 assays. Interestingly, and in contrast to [Leu31,Pro34]NPY and NPY13-36, the PYY derivatives [Leu31,Pro34]PYY and PYY3-36 were inactive in a purported Y3 bioassay (rat colon). These results suggest that [Leu31,Pro34]PYY and PYY3-36 respectively represent the first selective and potent Y1 and Y2 agonists, devoided of significant affinity/activity for the Y3 receptor class.

Randomised controlled trial of enalapril and beta blockers in non-diabetic chronic renal failure

OBJECTIVE

To compare the ability of angiotensin converting enzyme inhibitors and beta blockers to slow the development of end stage renal failure in non-diabetic patients with chronic renal failure.

DESIGN

Open randomised multicentre trial with three year follow up.

SETTING

Outpatient departments of six French hospitals.

PATIENTS

100 hypertensive patients with chronic renal failure (initial serum creatinine 200-400 mumol/l. 52 randomised to enalapril and 48 to beta blockers (conventional treatment).

INTERVENTIONS

Enalapril or beta blocker was combined with frusemide and, if necessary, a calcium blocker or centrally acting drug in patients whose diastolic pressure remained above 90 mm Hg.

RESULTS

17 patients receiving conventional treatment and 10 receiving enalapril developed end stage renal failure. The cumulative renal survival rate was significantly better in the enalapril group than in the conventional group (P < 0.05). The slope of the reciprocal serum creatinine concentration was steeper in the conventionally treated patients (-6.89 x 10(-5)l/mumol/month) than in the enalapril group (-4.17 x 10(-5)l/mumol/month; P < 0.05). No difference in blood pressure was found between groups.

CONCLUSION

In hypertensive patients with chronic renal failure enalapril slows progression towards end stage renal failure compared with beta blockers. This effect was probably not mediated through controlling blood pressure.

Characterization of endothelin (ET) receptors in the isolated gall bladder of the guinea-pig: evidence for an additional ET receptor subtype

1. We have characterized the receptors mediating contractions induced by endothelin-1 (ET-1), ET-2, ET-3 and the ETB-selective receptor agonists, sarafotoxin 6c (SX6c), IRL 1620, BQ-3020, [Ala1,3,11,15]ET-1 and ET (16-21) in strips of the isolated gall bladder of the guinea-pig (GPGB). We used as antagonists BQ-123 (ETA receptor selective) and PD 145065 (ETA/ETB receptor non-selective). 2. ET-1, ET-2 and ET-3 (10(-10) M to 3 x 10(-7) M) caused similar slowly-developing concentration-dependent contractions of the GPGB. Contractile effects induced by ET-1, ET-2 or ET-3 (at 3 x 10(-7) M) were also similar (230 +/- 25, 241 +/- 7 and 287 +/- 37% of that to histamine at 5 x 10(-6) M, n = 7, 6, 12, respectively). However, the threshold concentration for ET-1 or ET-2 was 10(-10) M whereas it was 3 x 10(-9) M for ET-3. 3. SX6c (10(-10) M to 3 x 10(-7) M) also caused slowly-developing concentration-dependent contractions at a threshold concentration of 10(-10) M (n = 16). However, the contraction caused by SX6c at 3 x 10(-7) M was 116 +/- 9% of that to histamine at 5 x 10(-6) M, which was half of that induced by the same concentration of the ET isopeptides. The contraction induced by IRL 1620 at 3 x 10-7 M (n = 9) was 43 +/- 9% of that to histamine at 5 x 10-6 M, which was one fifth of that produced by the same concentration of ET-1. Contractions induced by BQ-3020 or [Ala1,3,11,15]ET-I at 3 x 10-7 M were even less than those produced by IRL 1620. ET (16-21) was inactive up to 10-5 M. Addition of a concentration of 3 x 10-7 M of ET-1 to tissues with developed contractions induced by the bolus addition of 3 x 10-7 M SX6c caused a further contraction of the GPGB to the level observed with ET-1 alone at 3 x 10-7M (n = 8).4. BQ-123 (10-5 M) did not affect the concentration-response curve to ET-1 and the contraction induced by 3 x 10- M was also not affected (n = 5; 239 +/- 19% of histamine at 5 x 10-6 M). PD 145065(10-5 M) shifted the ET-1 concentration-response curve to the right and the contraction induced by ET-1at 3 x 10-7 M was inhibited by 15% (n = 6; NS). A higher concentration of BQ-123 (10-4 M) caused a significant shift to the right of the ET-1 concentration-response curve similar to that caused by PD 145065 (10-s M) and caused a 24% (n = 6; NS) inhibition of the contractions induced by ET-1 at 3 x 10-7 M. PD 145065 (10-4 M) abolished contractions induced by ET-1 (up to 10- M) and inhibited the response to ET-1 at 3 x 10-7 M by 52% (n = 4; P< 0.05).5. Contractions induced by ET-3 were more sensitive to inhibition by the antagonists. BQ-123 (10-6,10-5 or 10-4 M) inhibited responses to 3 x 10-7 M ET-3 by 66, 71 and 83%, respectively (n = 5, 5, 3;P< 0.05). PD 145065 (10-6, 10-5 or 10-4 M) attenuated more strongly than did BQ-123 the contractions induced by ET-3. For instance, the contractions caused by ET-3 at 3 x 10-7 M were decreased by 73 and 80% (n = 5, 5; P<0.05) in the presence of PD 145065 (10-6 or 10-5 M, respectively). PD 145065(10-4 M) completely abolished contractions to ET-3 (n = 4; up to 3 x 10-7M).6. Contractions induced by SX6c, especially those observed at concentrations lower than 10-8 M, were attenuated by BQ-123 (up to 10-4 M). PD 145065 (10-5M) shifted to the right the concentration response curve to SX6c and inhibited by 38% (P<0.05) the contractions induced by 3 x 10-7M.However, the contractions induced by a bolus addition of a high concentration of SX6c (3 x 10-7 M)and the subsequent addition of an identical concentration of ET-1 on top of SX6c were not affected byBQ-123 (10-6 or 10-5 M).7. These results suggest that ETB receptors are involved in the contractions induced by endothelins in the GPGB. However, SX6c and other selective ETB agonists produced only half or less than half of the contractile response induced by non-selective agonists. In addition, the responses to ET-1 but not to ET-3, were insensitive to the antagonist action of BQ-123 at 10-5 M whereas BQ-123 or PD 145065 at 10-5 M strongly antagonized contractions induced by ET-3. Finally, BQ-123 at 10-4 M inhibited contractions to ET-1 and SX6c. Thus, within the GPGB there may well be additional ET receptor(s) not conforming to the established ETA/ETB receptor subtype classification, as well as ETB receptors.

Autoradiographic distribution and receptor binding profile of [125I]Bolton Hunter-rat amylin binding sites in the rat brain

Amylin is a recently isolated peptide from amyloid plaques in noninsulin-dependent diabetic patients and showed high sequence homology with calcitonin gene-related peptide. We investigated the distribution and the binding profile of [125I]Bolton Hunter-rat amylin ([125I]BH-rat amylin) binding sites in the rat brain, as well as the affinity of rat amylin for [125I]hCGRP alpha binding sites in the brain, atrium (CGRP1 receptor-enriched tissue) and vas deferens (CGRP2 receptor-enriched tissue). High amounts of high affinity [125I]BH-rat amylin binding sites were observed in the nucleus accumbens, various hypothalamic nuclei, amygdaloid body, dorsal raphe, tegmental and parabrachial nuclei and the locus ceruleus. Interestingly, both rat amylin and salmon calcitonin revealed low nanomolar affinities (2-19 nM) for [125I] BH-rat amylin binding sites in the various brain areas, whereas human calcitonin gene-related peptide-alpha (hCGRP alpha) showed lower affinities ranging between 13 to 150 nM. Moreover, the affinity of rat amylin was much lower than that of hCGRP alpha for [125I]hCGRP alpha binding in the brain, atrium and vas deferens, except for very few areas such as the nucleus accumbens and ventral striatum. Similarly, rat amylin was much weaker (100- to 400-fold) than hCGRP alpha to induce a biological effect in the atrium and vas deferens. These results thus suggest the existence of unique [125I]BH-rat amylin binding sites in the rat brain as well as limited cross-reactivity between rat amylin and [125I]hCGRP alpha receptors present in the brain, atrium and vas deferens.

Adynamic bone disease in patients with uremia

Adynamic (or aplastic) bone disease is a bone histologic pattern characterized by decreased bone formation rate, low cellularity, and normal or decreased osteoid thickness. It was first described in symptomatic patients undergoing dialysis who were overloaded with aluminum because of contaminated dialysate or chronic ingestion of aluminic phosphate binders; the evidence of the overload was extensive coloration (more than 25%) with aurin tricarboxylic acid, whereas the Perls stain coloration for iron was negative. We have, however, reported these histologic changes in asymptomatic patients with uremia who were never exposed to aluminum, in two patients before end-stage renal failure and in six patients undergoing dialysis. The main step in the prevention of adynamic bone disease is the absolute exclusion of aluminum exposition even by so-called "safe doses" of aluminum phosphate binders because in the long term they are never actually safe. Because idiopathic adynamic bone disease may nevertheless occur, parathyroid hormone suppressive treatment by oral calcium taken with meals as phosphate binders (+/- 1 alpha-hydroxyvitamin D3 derivatives) should be carefully monitored by measurements of plasma concentrations of not only calcium and phosphate but also of intact parathyroid hormone levels. In order to have normal bone formation rate levels, patient intact parathyroid hormone levels should be between one and three times the upper limit of the normal level. Although adynamic bone disease may not be a true bone disease when not due to aluminum, it is a risk factor for increased incidence of hypercalcemia and hyperphosphatemia and therefore for metastatic calcifications. Therefore, when hypercalcemia occurs with hyperphosphatemia and normal intact parathyroid hormone in patients treated with 1 alpha-hydroxyvitamin D3, it is proposed that the latter drug should be discontinued first, whereas oral calcium is increased to correct hyperphosphatemia, and calcium concentration is decreased in the dialysate to prevent hypercalcemia, even though plasma parathyroid hormone may increase up to three times the upper limit of the normal level. In patients previously exposed to aluminum, a deferoxamine test should be performed and a deferoxamine treatment started if the test is positive.

Localization, identification, and action of calcitonin gene-related peptide in the frog adrenal gland

The localization of calcitonin gene-related peptide (CGRP)-like immunoreactivity in the adrenal gland of the frog, Rana ridibunda, was examined by the indirect immunofluorescence technique. Using an antiserum directed against rat alpha-CGRP, the presence of a network of positive fibers was observed in the adrenal parenchyma. The immunoreactive material has been characterized by HPLC analysis combined with RIA quantification. The elution profile revealed the existence of a single form of CGRP exhibiting the same retention time as synthetic frog CGRP. The possible involvement of CGRP in the regulation of corticosteroid secretion was studied in vitro using a perifusion system for frog adrenal slices. Graded doses of frog CGRP (from 3 x 10(-9) to 3 x 10(-6) M) increased corticosterone and aldosterone secretion in a dose-dependent manner (ED50, 4.1 x 10(-8) M). Several other forms of CGRP, i.e. rat alpha-CGRP and beta-CGRP, and human alpha-CGRP and beta-CGRP, were also capable of enhancing steroid output, but frog CGRP was the most effective stimulator of steroidogenesis. Repeated administration of rat alpha CGRP induced a reproducible stimulation of corticosteroid secretion without any tachyphylaxis. Prolonged infusion of the peptide (3 h) caused a rapid increase in corticosteroid release, followed by a gradual decline of steroid secretion, suggesting the occurrence of a desensitization phenomenon. Rat alpha-CGRP also gave rise to a significant increase in corticosteroid release from acutely dispersed adrenal cells. These results show the presence of CGRP in fibers innervating the frog adrenal gland. The data also demonstrate that synthetic CGRP exerts a direct stimulatory effect on corticosteroid secretion. Taken together, these findings suggest that CGRP, released by nerve fibers in the adrenal tissue, can locally regulate corticosteroid secretion.

Endothelin-1-induced myocardial ischaemia and oedema in the rat: involvement of the ETA receptor, platelet-activating factor and thromboxane A2

1. The objectives of the present experiments were to assess the role of ETA receptors in mediating endothelin-1 (ET-1)-induced myocardial ischaemia and oedema and to study the involvement of platelet-activating factor (PAF) and thromboxane A2 (TxA2) in these actions of ET-1 in rats. 2. Intravenous bolus injection of ET-1 (0.1-2 nmol kg-1) into anaesthetized rats induced ST segment elevation of the electrocardiogram in a dose-dependent manner without causing arrhythmias. ST segment elevation developed within 20-90 s and persisted for at least 10-20 min following administration of ET-1. 3. Pretreatment of the animals with the selective endothelin ETA receptor antagonist, FR 139317 (2.5 mg kg-1, i.v.) inhibited by 86% the ST segment elevation elicited by ET-1 (1 nmol kg-1). Pretreatment with intravenous administration of BM 13505 (1 mg kg-1), a TxA2 receptor antagonist, OKY-046 (10 mg kg-1), a thromboxane synthase inhibitor or the specific PAF receptor antagonist, WEB 2086 (1 mg kg-1) or BN 52021 (10 mg kg-1) markedly suppressed ST segment elevation in response to ET-1. Infusion of indomethacin (3 mg kg-1 bolus plus 2 mg kg-1 h-1) did not significantly affect ET-1-induced ST segment elevation. 4. Bolus injection of ET-1 (1 nmol kg-1, i.v.) to conscious rats resulted in a prolonged pressor effect preceded by a transient depressor response. Corresponding to changes in blood pressure, a small transient tachycardia was followed by a sustained bradycardia. ET-l enhanced albumin leakage by 87 and 120% in the left ventricle and right atrium, respectively, as measured by the extravasation of Evans blue dye.5. The selective ETA receptor antagonist, FR 139317 (2.5 mg kg-1) significantly blunted the pressor action of ET-1 and the accompanying bradycardia without affecting the depressor response. Furthermore,FR 139317 almost completely abolished the permeability effect of ET-l in both vascular beds studied.6. Pretreatment of the animals with BM 13505 (1 mg kg-1), OKY-046 (10mg kg-1), WEB 2086(1 mg kg-1) or BN 52021 (10mg kg-1) significantly reduced ET-1 (1 nmol kg-1)-induced albumin extravasation both in the left ventricle and right atrium. The PAF receptor antagonists, WEB 2086 and BN 52021 were equally potent inhibitors in the left ventricle, whereas BN 52021 appeared to be a more potent inhibitor than WEB 2086 in the right atrium. Pretreatment with indomethacin (3 mg kg-1 plus 2 mg kg-1 h-1) did not modify the permeability response to ET-1. None of these compounds affected significantly ET-l-induced changes in mean arterial blood pressure and heart rate.7. These results indicate that intravenous administration of ET-1 provokes ST segment elevation and myocardial oedema and suggest that these events are mediated, in part, through release of secondary mediators, such as PAF and TxA2 via the activation of ETA receptors.

[Results of vascular repairs in trauma of the femoral veins, iliac veins and the inferior vena cava]

We examined the records of 12 patients operated for lesions of the inferior vena cava, the iliac vein, or the common femoral vein were examined. The results of venous grafts, treatment of the lesions of the posterior inferior vena cava or the supra hepatic vena cava and the permeability after repair of these large vessels was studied. Treatment included simple suture (n = 9), venous patch (lateral iliac vein, n = 1), and venous autografts (common femoral veins, n = 2). For 3 lesions of the posterior or supra-hepatic inferior vena cava, haemostasis was obtain by double clamping (n = 2) or four-way clamping (n = 1) with right hepatectomy. In 9 cases, the patients were followed-up for a mean of 59 months. Morphologic exploration with phlebography (n = 1) or echo-Doppler examination (n = 7) was performed during the follow-up period. There were no post-operative deaths. There were no functional sequellae affecting the lower limbs. In one case, the echo-Doppler examination revealed repermeabilization of a thrombosed lateral iliac vein after simple suture. Lesion repair of large diameter veins with autografts using the internal jugular or internal saphenous vein gave good results. Haemostais of posterior or supra-hepatic lesions to the inferior vena cava was obtained with clamping. In cases with associated hepatic involvement, haemostasis was controlled with a four-way clamp and trans-hepatic access or digitoclasty. Long-term permeability of venous repair was good.

Binding profile of a selective calcitonin gene-related peptide (CGRP) receptor antagonist ligand, [125I-Tyr]hCGRP8-37, in rat brain and peripheral tissues

The calcitonin gene-related peptide (CGRP) C-terminal fragment human CGRP8-37 acts as a potent antagonist of various in vitro and in vivo effects of CGRP. Its iodinated counterpart, [125I-Tyr] hCGRP8-37, binds with high affinity (KD values between 7.5 x 10(-11)-2.1 x 10(-10) M) to what is apparently a single class of CGRP receptors in brain, atrium and vas deferens membrane preparations. The relative potencies of various CGRP-related fragments and analogs in competing for [125I-Tyr]hCGRP8-37 binding sites were similar in these three preparations, with hCGRP alpha being the most potent competitor, followed by unlabeled hCGRP8-37, the linear agonist [acetamidomethyl-cysteine2,7] hCGRP alpha, and finally by rat amylin-amide and salmon calcitonin. Competition profiles suggested the existence of a single affinity site (except in the case of hCGRP alpha, for which competition binding data were best fitted to two apparent affinity constants in all three tissues), whereas rat amylin-amide revealed two affinity constants in the rat brain. Guanylylimidodiphosphate (100 microM) failed to alter specific [125I-Tyr]hCGRP8-37 binding in the various tissues studied here. Quantitative receptor autoradiography in the rat brain revealed [125I-Tyr]hCGRP8-37 binding sites mostly concentrated in the nucleus accumbens (shell), caudate putamen (tail), amygdaloid body, pontine nuclei, cerebellum and inferior olive, whereas lower quantities of sites were present in the olfactory tubercle, nucleus accumbens (core), medial geniculate, superior colliculus, temporal cortex, inferior colliculus, lateral lemniscus, vestibular nuclei and principal sensory trigeminal nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

[Idiopathic dilatation of the pulmonary artery. Echocardiographic aspects]

The authors compared 30 patients with at least one clinical sign of idiopathic dilatation of the pulmonary artery, with a group of 20 normal control subjects in order to establish diagnostic criteria for this condition. In the first group, 17 had characteristic radiological findings and 13 others had clinical signs of idiopathic dilatation of the pulmonary artery. Comparison with the control group showed significant differences (p < 0.05) in 4 parameters: 1) the diameter of the pulmonary artery at the bifurcation/m2 body surface area (2.8 +/- o.4 cm versus 2.4 +/- 0.4 cm), 2) the diameter of the aorta 2 cm beyond the aortic valve/m2 of body surface area (1.7 +/- 0.3 cm versus 2.1 +/- 0.7 cm), 3) the ratio of pulmonary artery/aortic diameters at the valve rings (1.4 +/- 0.2 versus 1.1 +/- 0.02); 4) the ratio of the aorta 2 cm beyond the valve/aortic ring (1.02 +/- 0.07 versus 1.09 +/- 0.09). The diagnostic criteria of idiopathic dilatation of the pulmonary artery in the absence of cardiac or pulmonary disease are: 1) ratio of pulmonary artery diameter at its bifurcation/aortic ring diameter or 2 cm beyond the aortic valve of > or = 1.4; 2) ratio of pulmonary/aortic ring diameters > or = 1.5.

Characterization of ETB receptors mediating contractions induced by endothelin-1 or IRL 1620 in guinea-pig isolated airways: effects of BQ-123, FR139317 or PD 145065

1. We have characterized the receptors mediating contractions to endothelin-1 (ET-1) or IRL 1620, an ETB receptor selective agonist, in isolated strips of tissue prepared from different parts of the guinea-pig airways. We used as antagonists BQ-123 and FR139317 (ETA receptor-selective) and PD 145065 (ETA/ETB receptor non-selective). 2. ET-1 and IRL 1620 (10(-10) M to 10(-6) M) caused similar concentration-dependent contractions of strips of guinea-pig trachea and upper bronchus. In the guinea-pig trachea without epithelium or lung parenchyma, IRL 1620 was less potent than ET-1. 3. In the trachea, contraction to ET-1 (< 10(-8) M) was preceded by a transient relaxation which was inhibited by BQ-123 (10(-5) M) or FR 139317 (10(-5) M) or by the removal of the epithelium. The concentration-response curve to ET-1 in the trachea was shifted to the right by PD 145065 (10(-5) M to 10(-4) M). PD 145065 (10(-4) M) also inhibited the response to ET-1 (3 x 10(-7) M) by 55%. Contractions induced by IRL 1620 were not affected by BQ-123 (10(-6) M) or FR139317 (10(-6) M) but were significantly attenuated by 10(-5) M of either antagonist. PD 145065 at 10(-6) M strongly attenuated and at 10(-5) M abolished contractions induced by IRL 1620. 4. In the trachea, removal of the epithelium potentiated the effects of both agonists. BQ-123 (10-5 M)had no effect on contractions of the trachea without epithelium induced by ET-1, but FR139317 (10-5 M)caused a significant inhibition. PD 145065 (10-5 M to 10-4 M) caused a shift to the right of the ET-1 concentration-response curve without affecting the contractile effect at 3 x 10-7 M. All three antagonists inhibited contractions induced by IRL 1620.5. In the upper bronchus, BQ-123 (10-5 M) did not affect contractions induced by ET-1, whileFR139317 (10-5 M) attenuated (20-26%) only contractions induced by 1-3 x 10-7 M ET-1. PD 145065(10-5 M to 10-4 M) caused a shift to the right of the ET-1 concentration-response curve. The contractions induced by IRL 1620 were inhibited by BQ-123 or FR139317 (10-5M to 10-4 M). PD 145065(10-6 M) strongly inhibited contractions induced by IRL 1620 and PD 145065 (10-5 M) totally abolished them.6. The contractile action of ET-1 in the lung parenchyma was significantly and similarly attenuated by BQ-123 (10-5 M) or indomethacin (10-5 M), while FRI39317 (10-5 M) was less effective. PD 145065(10-6 to 10-5 M) inhibited contractions to ET-1. IRL 1620, which is less potent than ET-1 in this preparation, was antagonized by PD 145065 (10-5 to 10-6 M) but unaffected by BQ-123 (10-6 M to10-5M) or FR139317 (10-6 M).7. Thus, ETB receptors mediate contractions to ET-1 in all four guinea-pig airway preparations. In addition, contractions to ET-1 in the trachea and lung parenchyma are mediated in part by ETA receptors. In the latter tissue, these ETA receptors mediate contraction through the release of cyclooxygenase metabolites. Similarly, ETA receptors located on the epithelial cells also mediate the release of prostanoids in the trachea with epithelium but they are responsible for transient relaxations. Interestingly,contractions induced by IRL 1620 were more susceptible to inhibition by the different antagonists,most probably because it binds to the endothelin receptors in a reversible manner. High concentrations(10-5 M) of ETA-selective antagonists also inhibit responses to IRL 1620, most probably by an effect at ETB receptors in both the trachea and the upper bronchus.

Species specificity and organ, cellular and subcellular localization of the 100 kDa Ras GTPase activating protein

A p100-GAP isoform, generated by an alternative splicing mechanism that eliminates the 180 hydrophobic amino acids at the amino terminus of p120-GAP, has been described in human placenta, in addition to the known p120GAP and neurofibromin. This p100-GAP possesses full Ras-GTPase stimulating activity. p120-GAP is ubiquitously localized in the cytosol while the localization of p100-GAP is unknown. Here we have explored the precise localization of p100-GAP and show that p100-GAP is present only in extracts of primate placenta. It is abundant in both human and Maccaca Rhesus placentae, where it is present in far larger amounts than p120-GAP. The p100-GAP is species-specific since it was not detected in the placenta of pig, sheep, mouse or rat. p100-GAP was also found to be organ-specific, since it was not detectable in organs other than the placenta. In this connection, we substantiated our previous finding that p100-GAP is mainly localized in the trophoblasts. Both subcellular trophoblast fractionation and immunofluorescence analyses showed that this protein was distributed between the cytosol, plasma membrane and a fraction bound to the nucleus, but not inside it. This highly restrictive specificity of p100-GAP localization in relation to species, organ and cell type, confirms the extreme singularity of this protein, and strongly suggests a particular specific function in the trophoblast.

Comparison of PD 145065 and Ro 46-2005 as antagonists of contractions of guinea-pig airways induced by endothelin-1 or IRL 1620

Cumulative concentrations of endothelin-1 or IRL 1620 (Suc-[Glu9,Ala11,15]endothelin-1-(8-21)), and endothelin ETB receptor selective agonist were similarly potent in contracting guinea-pig upper bronchi, whereas endothelin-1 was more potent than IRL 1620 in contracting lung parenchymal strips. PD 145065 (10(-5) M and 10(-4) M), a non-selective endothelin ETA/ETB receptor antagonist (Ac-D-Bhg-L-Leu-L-Asp-L-Ile-L-Ile-L-Trp), significantly attenuated the contractions induced by endothelin-1 in either preparation whereas Ro 46-2005 (3 x 10(-5) M and 10(-4) M), a non-peptide non-selective receptor antagonist (4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-5-3-methoxy-phenoxy)-4-pyrimidinyl (benzenesulfonamide)), was without effect. PD 145065 (10(-6) M and 10(-5) M) also strongly inhibited contractions induced by IRL 1620, whereas Ro 46-2005 caused much less antagonism. Thus, PD 145065 is a more potent antagonist than Ro 46-2005 of contractions induced by endothelin-1 or IRL 1620 and mediated by endothelin ETB receptors in these guinea-pig airway preparations.

Involvement of ETA receptors in the facilitation by endothelin-1 of non-adrenergic non-cholinergic transmission in the rat urinary bladder

1. Endothelin-1 (ET-1; 3-10 nM) raised the tone of rat bladders bathed in buffer containing atropine (1 microM) plus guanethidine (3.4 microM). In addition, ET-1 potentiated, in a concentration-dependent fashion (1-10 nM), the contractions evoked by both transmural nerve stimulation and applications of exogenous adenosine 5'-triphosphate (ATP). 2. The threshold concentration of ET-1 required to facilitate non-adrenergic non-cholinergic (NANC) transmission and potentiate ATP-induced contractions, was about 10 fold lower than that required to increase the bladder tone (3 nM). 3. The ET-1-induced increase in basal tension reached its maximal effect within 60-90 s. In contrast, the 7.8 microM ATP-induced contractions increased by 50% within the first minute following incubation with 10 nM ET-1 but required about 5 min to develop the maximal effect. 4. The ET-1-induced potentiation of NANC or ATP responses was long-lasting and persisted in spite of extensive washing. The recovery of the bladder excitability depended on the concentration of ET-1. Following the application of 3 nM ET-1, recovery required 30 min; applications of 10 nM ET-1 required at least 60 min for full recovery. 5. The ET-1-induced potentiation of responses was selective for ATP and related structural analogues. ET-1 did not modify the contractions induced by acetylcholine, 5-hydroxytryptamine, prostaglandin F2 alpha or bradykinin. 6. The potency of ET-2 was similar to that of ET-1. ET-3 and ET-C-terminal hexapeptide were inactive up to 100 M. Sarafotoxin S6b was 2 to 3 fold less potent than ET-1 whereas sarafotoxin S6c (100 nM) was inactive. AGETB-9 and AGETB-89, two ETB receptor agonists, were also inactive (up to 100 nM). 7. Removal of one or both disulphide bonds in ET-1 and tryptophan-21 formylation of ET-1, resulted in inactive peptides (up to 100 nM). 8. The ET-1 receptor antagonists, BE-18257B and FR 139317, blocked both the ET-1-induced rise in tone and the potentiation of ATP responses in a concentration-dependent fashion. FR 139317 was at least 30 fold more potent than BE-18257B. Both antagonists blocked at lower concentrations the ET-1 increase in bladder tone as compared to the ATP potentiation. The antagonism was slowly reversible. 9. Results are consistent with the presence of ETA receptors in the rat bladder, which mediate both actions of ET-1. The interaction of ET-1 with purinergic mechanisms is discussed.

Catheter ablation using radiofrequency or low-energy direct current in pediatric patients with the Wolff-Parkinson-White syndrome

Percutaneous ablation of accessory pathways was performed in 22 consecutive children and adolescents (9 boys and 13 girls, age range 8 to 18 years). Low-energy direct current (DC) was used exclusively in the first 6 patients, whereas ablation was performed with radiofrequency energy in the following 16. Accessory pathways were located in the left free wall in 15 patients, were posteroseptal in 3, were in the right free wall in 3 and were anteroseptal in 1. A concealed accessory pathway was present in 7 patients (32%). There was no significant difference in clinical or electrophysiologic variables between both groups. Catheter ablation was successful in the initial 6 patients using low-energy DC, as compared with 13 of 16 patients using radiofrequency ablation. Low-energy DC was successful as a backup power source in all 3 patients who had unsuccessful radiofrequency ablation. There was no complication. The median procedural and fluoroscopic times for successful ablation were 2.5 hours and 49 minutes, respectively (p = NS between both power sources). Accessory pathway conduction recurred in 2 patients (33%) who had low-energy DC as compared with 1 (6%) who had radiofrequency ablation (p = NS). These 3 patients had successful reablation of their accessory pathways. In children and adolescents with accessory pathways, both new power sources compare favorably, with an overall success rate of ablation of 100% (22 of 22 patients). Radiofrequency ablation should be used initially because it does not require general anesthesia and is associated with a lower rate of recurrence of accessory pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo central actions of NPY(1-30), an N-terminal fragment of neuropeptide Y

The purpose of the present study was to examine the possible central actions of a N-terminal fragment of NPY, NPY(1-30), on five measures typically influenced by the native peptide: decreased spontaneous activity, enhancement of muscle tone (increased grasping response), catalepsy, hypothermia, and stimulation of food intake. The peptides were administered ICV in doses ranging from 2.5 to 160 micrograms (0.75-48 nmol) and their effects on the three motor variables as well as thermal and feeding responses were evaluated and compared. Globally, results indicate that, similarly to NPY, the N-terminal fragment NPY(1-30), decreased spontaneous activity and induced hypothermia. However, the fragment displayed approximately half of the potency of NPY for producing these effects. On the other hand, contrary to NPY, NPY(1-30) did not affect muscle tone or food consumption and did not induced catalepsy in animals. These results demonstrate for the first time central actions of a N-terminal fragment of NPY and lend further support to the hypothesis that the receptors mediating the central actions of NPY are pharmacologically different.

Aging differentially modifies arterial sensitivity to endothelin-1 and 5-hydroxytryptamine: studies in dog coronary arteries and rat arterial mesenteric bed

The influence of age on vascular reactivity to endothelin-1 (ET-1) and 5-hydroxytryptamine (5-HT) was studied in coronary artery rings from dogs of 9 years of age or younger, and dogs older than 9 years. ET-1 caused concentration-dependent contractions that developed about 100% of the 70 mM KCl-induced tension in the younger dogs; those from older dogs did not generate more than 20%. In contrast, 5-HT developed only about 20% of the KCl-induced tension in rings from young dogs, whereas in the older animals, it developed up to 120% of the KCl tension. No significant difference in the tension developed by 70 mM KCl was noted between both groups of dogs. Mechanical denudation of the endothelial cell layer caused a modest, yet significant, leftward shift of the ET-1 and 5-HT concentration-response curves only in the younger dogs. N omega-Nitro-L-arginine (15 microM) shifted the ET-1 concentration-response curves to the left in rings from both groups of dogs. Rings precontracted with 20 mM KCl relaxed in a concentration-dependent fashion with acetylcholine; its sensitivity was about threefold less in the older group of dogs. To validate the changes in vascular reactivity with age, a parallel study was performed perfusing the arterial mesenteric bed of rats of 3, 7, and 30 weeks of age. In this experimental model, the efficacy of ET-1 significantly decreased with age and that of 5-HT was significantly increased. The vasomotor reactivity of noradrenaline was modestly affected by aging, whereas the acetylcholine-induced vasorelaxation was significantly reduced with age.