Bombesin-like immunoreactivity in the avian gut and its localisation to a distinct cell type

Summary The distribution of a bombesin-like immunoreactive peptide in the avian gastro-intestinal tract was analysed by combined radioimmunoassay and immunocytochemistry. Radioimmunoassay of tissue extracts showed that the largest quantities of bombesin-like immunoreactivity were present in the proventriculus (64.5±6.0 pmol/g) with smaller but still considerable amounts in the gizzard (40.0±6.0 pmol/g). Immunocytochemically the extractable bombesin-like immunoreactivity was localised in numerous endocrine cells. These, in the proventriculus, were found mainly in the deeper layers of the mucosa. Further study of these cells by the semi-thin/thin technique revealed the presence of characteristic secretory granules. The functional name BN is proposed for this cell type.     

Distribution of vasoactive intestinal peptide, bombesin, and gastrin-cholecystokinin like peptides in the avian intestinal tract and brain

The distribution of vasoactive intestinal peptide (VIP), bombesin and gastrin-cholecystokinin in the chicken was studied by radioimmunoassay of tissue extracts. VIP was present in high concentrations in colon (186 +/- 29 pmol/g), cloaca (116 +/- 27 pmol/g), jejunum (97 +/- 14 pmol/g) and pancreas (15 +/- 3 pmol/g) but not detected in lung, liver or thymus. The highest concentration of bombesin was in the proventriculus (92 +/- 13 pmol/g), negligible in remaining gut but found in brain. Gel chromatography indicated two forms of bombesin: one form eluting with bombesin-14 and the other with gastrin releasing peptide. Gastrin-like immunoreactivity was found in low levels in the gut and brain. The concentrations were higher with an antiserum which cross reacted with the carboxy terminus common to gastrin-17 and CCK compared to a gastrin specific antisera (P less than 0.01). This suggests that the carboxy terminal region has been conserved during evolution. Each distribution pattern of bombesin, VIP and gastrin CCK is different, and distinct from that found in mammals, suggesting specific roles for these peptides in birds.     

Ontogeny of immunoreactive CCK and VIP in pig brain and gut

The concentrations and hormonal forms of CCK and VIP have been determined in extracts of the brain and duodenum of the developing and adult pig. In methanol extracts of the brain cortex, the single hormone form, CCK8, increased from 130 +/- 20 (Mean +/- SEM) pmol/g at birth to an adult level of 300 +/- 50 pmol/g. In acid extracts of brain, the predominant immunoreactive form had N-terminal immunoreactivity and increased from 240 +/- 20 pmol/g at birth to an adult level 490 +/- 30 pmol/g; the C-terminal immunoreactivity was about 10-fold lower. The concentrations and hormonal forms of immunoreactive CCK in duodenal extracts did not appear to be age-related. C-terminal immunoreactivity in methanol extracts averaged 140 +/- 20 pmol/g and in acid extracts 240 +/- 60 pmol/g. The concentration of N-terminal immunoreactivity in acid extracts averaged 490 +/- 70 pmol/g. The VIP concentrations in acid extracts of the brain cortex was 13.5 +/- 2 pmol/g at birth and rose gradually to 30 +/- 9 pmol/g in the adult; in duodenal extracts it was 240 +/- 18 pmol/g at birth and 195 +/- 38 pmol/g in the adult. These results are in marked contrast with the ontogeny of these hormones in the rat in which brain concentrations of CCK and VIP in the neonate are less than 10% of adult levels and in which there are age-related changes in the content of these hormones in the duodenum as well.     

Bombesin-like peptides in small cell lung cancer: biochemical characterization and secretion from a cell line

High intracellular levels of BN-like peptides are present in tumors and cell lines of small cell carcinoma of the lung (SCCL) as well as the putative precursor cells of this tumor, the pulmonary endocrine cell. In cell line NCI-H209 the density of bombesin-like peptides was 8.9 +/- 1.1 pmol/mg total protein. Gel filtration chromatography of an extract of these cells revealed one major peak of immunoreactivity which coeluted with synthetic bombesin (1620 daltons). Also, high pressure liquid chromatography revealed one major peak of immunoreactivity was present which eluted before synthetic peptide. Therefore, SCCL bombesin-like peptides may be of similar size but are more hydrophilic than synthetic peptide. Cells maintained in culture continuously release bombesin-like peptides into the growth medium. Also, high concentrations of K+ stimulated the secretion of immunoreactive bombesin from cell lines in a Ca++-dependent manner. These SCCL bombesin-like peptides may function as important regulatory agents in the malignant lung.     

Immunochemical characterisation of somatostatin in ruminants

Following development and validation of a radioimmunoassay for somatostatin, the immunoreactivity of this peptide in the plasma of ruminants was measured and the levels in sheep were 9-31 pM (mean 18 +/- 7 pM, n = 48), in lambs 10-54 pM (mean 25 +/- 10 pM, n = 18) and in calves 5-35 pM (mean 12 +/- 6 pM, n = 22). Somatostatin-like immunoreactivity was present in sheep in high concentrations in the antrum (2342 +/- 280 pmol/g wet weight), duodenum (446 +/- 73 pmol/g) and pancreas (832 +/- 208 pmol/g). Lower concentrations (6-150 pmol/g) were found in other regions of the gastrointestinal tract. Molecular sieve chromatography on Bio-Gel P-10 showed that while most of the somatostatin in the antrum was somatostatin-14, in the duodenum about 30% of the total immunoreactivity was somatostatin-28.     

Mapping, quantitative distribution and origin of substance p- and VIP-containing nerves in the uvea of guinea pig eye

VIP- and substance P-like immunoreactivities were found in considerable concentrations (VIP: 17.3 +/- 4.8 pmol/g, mean +/- SEM; substance P:11.1 +/- 1.8 pmol/g) in the uveal portion of the guinea pig eye. Immunocytochemistry localised these two regulatory peptides to nerve fibres found principally in a plexus in the iris (substance P) and in an extensive network surrounding the blood vessels of the choroid (VIP). A remarkable anatomical demarcation of the two types of peptide-containing nerves was established by the staining of substance P-containing nerves, which stops at the level of the ciliary body. This uveal area is known to be involved in the ocular responses to nociceptive stimuli. At the ultrastructural level, immunoreactivity for both peptides was localised to distinct subpopulations of p-type nerves, distinguishable by the size of their large dense-cored vesicles. Those immunoreactive for VIP were significantly larger (p less than 0.0005) than those immunoreactive for substance P (95 +/- 7 nm and 82 +/- 9 nm respectively; mean +/- SD). Interruption of the trigeminal pathway produced a remarkable decrease of substance P immunoreactivity in the anterior portion of the uvea (9.1 +/- 1.5 pmol/g, mean +/- SEM, control; 5.3 +/- 1.3 pmol/g, denervated), but not of VIP immunoreactivity in the choroid. Following colchicine treatment, VIP-immunoreactive neuronal cell bodies were localised in the choroid. The separate anatomical localisations and distributions of the two uveal peptides appear to be related to their different origins and functional roles in the response of the eye to noxious stimuli.     

Bombesin-like immunoreactivity in the nervous system of hydra

Summary With immunocytochemical methods, nerve cells have been detected in Hydra attenuata containing bombesin-like immunoreactivity. These nerve cells are located in the ectoderm of all body regions of the animal and are especially abundant in basal disk and tentacles. Radioimmunoassay of extracts of hydra demonstrated at least 0.2 pmol/g wet weight of bombesinlike immunoreactivity. The immunoreactive material elutes from Sephadex G-50 in a similar position to synthetic bombesin. The data show that bombesin-like peptides are among the phylogenetically oldest neuropeptides found so far.     

The distribution of GAWK-like immunoreactivity in neuroendocrine cells of the human gut, pancreas, adrenal and pituitary glands and its co-localisation with chromogranin B

GAWK is a recently discovered peptide isolated from extracts of human pituitary gland and subsequently shown to be identical to sequence 420-493 of human chromogranin B. The distribution of this peptide was studied in human gut, pancreas, adrenal and pituitary glands using antisera to two portions of the 74 amino acid peptide (sequences 1-17 and 20-38). In addition, the co-existence of GAWK immunoreactivity with other peptides and chromogranin B was investigated using comparative immunocytochemistry. In the gut, GAWK was localised mainly to serotonin-containing cells of the mucosal epithelium, where electron microscopy showed it to be stored in typical electron-dense (250 nm diameter) granules, and to a moderate population of nerve fibres in the gut wall. Considerable quantities of GAWK-like immunoreactivity were measured in the gut, up to 36.3 +/- 18 pmol GAWK 1-17/g wet weight of tissue (mean +/- SEM) and 12.4 +/- 2.9 pmol GAWK 20-38/g. Chromatography of gut extracts revealed several GAWK-like immunoreactive peaks. GAWK-like immunoreactivity was also detected in endocrine cells of pancreas, pituitary gland and adrenal medulla, where the highest concentrations of GAWK-like immunoreactivity were measured (GAWK 1-17 2071.8 +/- 873.2 and GAWK 20-38 1292.7 +/- 542.7 pmol/g). Endocrine cells containing GAWK-like immunoreactivity were found also to be immunoreactive for chromogranin B. Our results define a discrete distribution of GAWK immunoreactivity in human endocrine cells and nerves and provide morphological support for the postulated precursor-product relationship between chromogranin B and GAWK. Details of the functions of this peptide are awaited.     

Distribution and heterogeneity of immunoreactive cholecystokinin (CCK) in the mucosa of the porcine gastrointestinal tract

The concentration and molecular nature of cholecystokinin-like immunoreactivity (CCK-LI) in extracts of porcine intestinal mucosa were determined using sequence-specific radioimmunoassays. Highest CCK concentrations were measured in duodenal mucosa (258 +/- 60 pmol/g in the distal duodenum) followed by jejunal mucosa (204 +/- 36 pmol/g in the proximal jejunum) and pylorus (51 +/- 9 pmol/g). All other gastrointestinal regions proximal to the pylorus and distal to the jejunum contained less than 20 pmol/g. Pancreas contained less than 1 pmol/g. Gel chromatography in 6 M urea revealed four immunoreactive forms and this was confirmed by reverse-phase high-pressure liquid chromatography (HPLC). The predominant molecular form in acid extracts of duodenal mucosa resembled CCK-33 although high concentrations of the larger CCK form ('CCK-58') and of the form intermediate in size between CCK-33 and CCK-8 were measured. A molecular form resembling CCK-8 was the principal form in neutral extracts of the duodenum.     

Localization of horseradish peroxidase (HRP)-anti-HRP complexes in cryostat sections: Influence of endotoxin on trapping of immune complexes in the spleen of the rat

Substance P-like immunoreactivity (SPLI) was studied by immunocytochemistry and radioimmunoassay in the cerebral arteries, choroid plexus and dura mater of the guinea-pig, rabbit, cat and man. The highest concentrations were found in cerebral blood vessels: 6.1 +/- 2.3 pmol/g (guinea-pig), 9.0 +/- 1.1 pmol/g (rabbit), 7.1 +/- 0.4 pmol/g (cat), and 2.4 +/- 0.9 pmol/g (man). Lower levels were obtained in the choroid plexus and dura mater. The distribution of substance P (SP)-immunoreactive nerve fibres found in various regions of the guinea-pig correlated well with the amount of SPLI measured. Sympathectomy did not alter the concentration of SPLI in the dura mater or in cerebral blood vessels. Electrical field stimulation or 124 mM potassium enhanced the spontaneous efflux of SPLI by 10 and 20%, respectively, from superfused pial arteries in vitro. These data are in support of a functional role of perivascular SP within the cranial circulation.     

Chromatographic evidence for high-molecular-mass galanin immunoreactivity in pig and cat adrenal glands

Galanin was measured by radioimmunoassay in extracts of pig, cat and rat adrenals using non-C- and mid to C-terminally directed antibodies. The extracts were fractioned by gel chromatography and HPLC. The non-C-terminal galanin immunoreactivity in pig was 92.8 +/- 11.7 pmol/g, in cat 9.1 +/- 0.9 pmol/g and in rat less than 1 pmol/g. Two higher molecular forms of galanin have been identified in both pig and cat adrenal. One major large form behaves as if it was N-terminally extended (Kav pig 0.58, cat 0.48) and the other, a very high-molecular-mass form (Kav pig 0.10, 0.24, cat 0.10), as if it had both N- and C-terminal extensions.     

Effects of solution of low pH and taurocholate on release of beta-endorphin-like immunoreactivity from human duodenal mucosa in vitro

The presence of beta-endorphin-like immunoreactivity (beta-EpLI) in human duodenum and its release were studied. beta-EpLI was detected in the duodenum (mucosa, 26.7 +/- 6.3 pmol/g wet weight, mean +/- SEM; remaining tissue 23.1 +/- 5.3 pmol/g wet weight) and the stomach (7.1 pmol/g wet weight). The two activities gave similar curves for inhibition of beta-Ep radioimmunoassay of synthetic beta-Ep. On gel-filtration chromatography of a duodenal extract, two components of beta-EpLI were separated. When human duodenal mucosa was perfused with a solution of pH2 or 1mM or 5mM taurocholate, the release of beta-EpLI from mucosa into the perfusate increased 2-4 fold. These results indicate that beta-EpLI present in human duodenal is released by the direct action of low pH or taurocholate on the duodenal mucosa and suggest that it may have a physiological role.     

Endocrine cells with gastrin/cholecystokinin-like immunoreactivity in the pancreas of the spiny dogfish,Squalus acanthias

Endocrine cells containing gastrin/cholecystokinin (CCK)-like immunoreactivity were localized to the islet tissue in the pancreas of the spiny dogfish. Most of these cells were located in the 'intestinal' lobe of the pancreas; only occasional cells were observed in the 'splenic' lobe. The gastrin/CCK-like immunoreactive cells were often co-localized with the 'classical' pancreas hormones (insulin, glucagon and somatostatin). Radioimmunoassay of water extracts with a C-terminally directed antiserum revealed high levels of immunoreactive material in the intestinal part (48.6 +/- 19.9 pmol/g) and lower levels (4.5 +/- 0.6 pmol/g) in the splenic part. Acetic acid extracts of the intestinal lobe contained low levels (6.8 +/- 3.3 pmol/g) of gastrin/CCK-like immunoreactivity, whereas corresponding extracts of the splenic part showed no immunoreactivity. When the extracts were subjected to DEAE ion-exchange chromatography the gastrin/CCK-like peptides eluted as a major peak. After Sephadex gel filtration, pooled immunoreactive material from the main DEAE chromatographic peak eluted at a position close to that of CCK4. Further characterization by ion-exchange and reversed-phase HPLC showed that, in general, the immunoreactive material behaved like the shorter forms of the gastrin/CCK family (CCK4/G5 and CCK8/Cae 3-10).     

Capsaicin releases calcitonin gene-related peptide from the human iris and ciliary body in vitro.

Slices of human iris or ciliary body, obtained post-mortem (8-12 h after death, n = 5), were superfused in vitro with capsaicin (10 microM) and the immunoreactivity for substance P (SP-LI) or calcitonin gene-related peptide (CGRP-LI) was measured in the effluent. In the iris and in the ciliary body CGRP-LI was 3.71 +/- 0.74 pmol/g and 3.01 +/- 0.55 pmol/g and SP-LI was 6.68 +/- 0.75 pmol/g and 6.55 +/- 0.84 pmol/g, respectively. A first exposure to capsaicin increased the CGRP-LI outflow from the ciliary body (427 +/- 46 fmol/g/30 min), whereas a second challenge with the drug 30 min later, failed to significantly enhance the CGRP-LI outflow (21.8 +/- 15.6 fmol/g/30 min). Likewise, the capsaicin-evoked increase in CGRP-LI outflow from the iris slices (472 +/- 62 fmol/g/30 min) was no longer observed at the second drug administration (38.4 +/- 12.8 fmol/g/30 min). Capsaicin failed to increase the SP-LI outflow from either the iris or the ciliary body. Reverse phase HPLC analysis of CGRP-LI indicated that authentic CGRP was contained in the tissue and in the superfusate collected during exposure to capsaicin. The present results show that in the human iris and ciliary body, capsaicin releases CGRP possibly contained in terminals of sensory nerves.     

Distribution and molecular forms of peptides containing somatostatin immunodeterminants in extracts from the entire gastrointestinal tract of man and pig

Specimens from human porcine mucosal and muscular tissue from the entire gastrointestinal tract were extracted in acid ethanol, subjected to chromatography and analysed for somatostatin-like immunoreactivity by region-specific radioimmunoassays. The concentration of somatostatin-like immunoreactivity from man and pig ranged from 1.13 +/- 0.37 to 101.15 +/- 33.93 pmol/g wet weight, and from 7.64 to 159.48 +/- 23.79 pmol/g wet weight, respectively. In both species the highest concentrations were found in the jejunum. The immunoreactivity in intestinal mucosal extracts was distributed among four major peaks, two of which were identified by HPLC as somatostatin 1-28 and somatostatin 1-14, respectively. A peak of approx. 10 kDa was resolved by ion exchange plus HPLC into three components, two containing at least part of the somatostatin 1-14 sequence as well as (part of) the somatostatin 1-28(1-14) sequence (but differing in charge), the third containing only the 1-28(1-14) sequence. These peptides probably represent uncleaved and partially cleaved prosomatostatin. The fourth component to be identified by gel filtration was slightly larger than somatostatin 1-14. Extracts from the antrum, the pancreas and from muscular tissues contained almost exclusively somatostatin 1-14, and very little somatostatin 1-28, indicating that the somatostatin precursor is processed differently at these sites. Furthermore, extracts of porcine gastric antrum, analysed for somatostatin 1-28(1-14) immunoreactivity, showed two immunoreactive forms in the mucosa and three major forms in the muscular layers.     

Pancreatic polypeptide-like material in nerves and endocrine cells of the rat

A region-specific antiserum (AbS11) raised against the carboxyl-terminal hexapeptide of pancreatic polypeptide has been employed to measure rat pancreatic polypeptide specifically and to demonstrate apparent immunoreactivity in nerves and in endocrine cells outside the pancreas. The concentration of pancreatic polypeptide in the head of the rat pancreas measured with AbS11 (176 +/- 47 pmol/g) was 750 fold higher than that measured with a conventional anti-bPP antiserum (0.23 +/- 0.08 pmol/g). Column chromatographs of rat pancreatic extracts demonstrated two peaks of immunoreactivity both eluting after the porcine pancreatic polypeptide standard. AbS11 also detected specific immunoreactivity in rat brain (470 fmol/g) which went undetected in convention assays. Although immunohistochemical studies with AbS11 and human pancreatic polypeptide antiserum demonstrated immunoreactivity in the same population of pancreatic endocrine cells, immunoreactive nerve fibres and enteroglucagon cells were only demonstrable with AbS11. These studies demonstrate that the carboxyl terminus of rat pancreatic polypeptide is immunochemically similar to that of higher mammals. Furthermore, neural and extrapancreatic endocrine variants of this peptide share an immunochemical determinant contained within the carboxyl-terminal hexapeptide.     

Calcitonin gene-related peptide: a sensory and motor neurotransmitter in the feline lower esophageal sphincter

The effect of calcitonin gene-related peptide (CGRP) on the feline lower esophageal sphincter (LES) was determined and correlated with its anatomic distribution as determined by immunohistochemistry. Intraluminal pressures of the esophagus and LES were recorded in anesthetized cats. In separate cats, gastroesophageal junctions were removed after locating the LES manometrically and stained for CGRP-like immunoreactivity (LI) and substance P-LI (SP-LI) by indirect immunohistochemistry. CGRP-LI in the LES was most prominent in large nerve fascicles between the circular and longitudinal muscle layers and only rarely seen in nerve fibers within the circular muscle. The myenteric plexus contained numerous CGRP-LI nerve fibers but cell bodies were not seen. Many CGRP-LI nerve fibers in the myenteric plexus and occasional varicose nerves in the circular muscle demonstrated colocalization with SP-LI. Colocalization of CGRP-LI with SP-LI was also seen in the perivascular nerves of the submucosal and intramural blood vessels and in varicose fibers in the lamina propria of the gastric fundic mucosa. In the esophagus, CGRP-LI nerves extended through the muscularis mucosa and penetrated the squamous epithelium to the lumen. CGRP, given intra-arterially caused a dose-dependent fall in basal LES pressure, with a threshold dose of 10(-8) g/kg (2.63 pmol/kg). At the maximal effective dose, 5 x 10(-6) g/kg (1.31 x 10(3) pmol/kg), CGRP produced 61.0 +/- 6.0% decrease in basal LES pressure. At this dose, mean systemic blood pressure fell by 40.9 +/- 7.8%. The LES relaxation induced by a submaximal dose of CGRP (10(-6) g/kg, 262.7 pmol/kg), 50.3 +/- 3.2% relaxation was partially inhibited by tetrodotoxin (26.9 +/- 10.8% relaxation, P less than 0.025). The inhibitory effect of CGRP was not affected by cervical vagotomy, hexamethonium, atropine, propranolol, or naloxone. The LES contractile response to the D90 of SP (5 x 10(-8) g/kg, 37.1 pmol/kg) was not altered by CGRP 10(-8) or 10(-6) g/kg and the CGRP relaxation effect was not altered by the threshold dose of substance P (5 X 10(-9) g/kg, 3.71 pmol/kg). CONCLUSIONS: (1) CGRP-LI is present at the feline LES and is primarily seen in large nerve fascicles which pass from the intermuscular plane and through the circular muscle layer to the submucosa and in mucosal nerves. (2) CGRP colocalizes with SP-LI in some varicose nerve fibers of the circular muscle of the esophagus, LES and fundus, in perivascular nerves of the submucosal and intramucosal blood vessels, and in nerves of the lamina propria of the gastric fundus. (3) The luminal penetration of CGRP-LI nerves in the squamous mucosa of the esophagus suggests a sensory func     

Phospholipid hydroperoxide accumulation in liver of rats intoxicated with carbon tetrachloride and its inhibition by dietary alpha-tocopherol

The formation and accumulation of phospholipid hydroperoxides, especially of phosphatidylcholine hydroperoxide (PCOOH), a primary peroxidation product of phosphatidylcholine (PC), in livers of carbon tetrachloride-intoxicated rats was investigated. PCOOH in liver and blood plasma was measured by a chemiluminescence-high-performance liquid chromatography procedure originally developed by Miyazawa et al. (Anal. Lett. 20, 915, 1987; Free Radical Biol. Med. 7, 209, 1989). Male Sprague-Dawley rats (120 g body wt., 5 weeks of age) were used in the experiments. The amount of PCOOH in the liver of control rats (CCl4-untreated) was 160 +/- 20 pmol/100 mg protein (mean +/- SD) and the PCOOH/PC molar ratio was 1.1 +/- 0.1 X 10(-5). In CCl4 (0.1 ml/100 g body wt.)-dosed rats, the liver PCOOH was 289 +/- 65 pmol/100 mg protein (PCOOH/PC = 2.4 +/- 0.4 X 10(-5], 764 +/- 271 pmol/100 mg protein (PCOOH/PC = 5.2 +/- 1.7 X 10(-5], and 856 +/- 165 pmol/100 mg protien (PCOOH/PC = 6.0 +/- 0.8 X 10(-5] at 6 h, 24 h, and 1 week after the dose, respectively. Under such conditions, the liver phosphatidylethanolamine hydroperoxide (PEOOH) level was not altered and the concentration was less than 100 pmol/100 mg protein even after the dose. The increments of liver PCOOH were suppressed 56% by the oral supplementation of DL-alpha-tocopherol (5 mg/100 g body wt./day) for a week before CCl4 administration. A relatively larger amount of PEOOH was found after stimulation of PC hydroperoxidation in the liver of rats with a large amount of CCl4 (0.25 ml/100 g body wt.) rather than with the small amount of CCl4 (0.1 ml/100 g body wt.).(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunocytochemical and ultrastructural characterization of endocrine cells in chicken proventriculus

Summary The endocrine cells of the chicken proventriculus were investigated immunocytochemically, using the peroxidase-antiperoxidase technique on paraffin and semithin sections for light microscopy, and immunogold staining in osmium-fixed material for electron microscopy. The fixation procedure also allowed a detailed ultrastructural investigation. Twenty-three antisera were tested and 7 immunoreactive cell-types were identified: D-cells containing somatostatin-like peptide; EG-cells immunoreactive to anti-glucagon, anti-GLP1 and antineurotensin; NT-cells labelled only with anti-neurotensin; BN-cells containing bombesin-like material; ENK-cells showing met-enkephalin immunoreactivity; EC-cells reactive to anti-serotonin; and APP-cells positive to anti-avian pancreatic polypeptide. In addition, enterochromaffin-like (ECL) cells, were also detected by electron microscopy. The presence of ENK-cells and the ultrastructure of these and NT-cells are described for the first time in chicken proventriculus, and glucagon, GLP1 and neurotensin are shown to be colocalized in the EG-cells.     

Tissue specific distribution, clearance and vascular effects of endothelin in the pig

Endothelin-like immunoreactivity (-LI) was detected in the kidney, spleen, skeletal muscle, lung and in plasma of the pig. The highest tissue levels were found in the lung (1.5 +/- 0.07 pmol/g) and the lowest in the muscle (0.08 +/- 0.02 pmol/g). I.v. infusion of endothelin (20 pmol/kg/min for 20 min) increased plasma endothelin-LI from 18 +/- 3 to 628 +/- 109 pM and renal, splenic and femoral vascular resistance by 570, 430 and 50%, respectively. There was a close correlation between the increase in plasma endothelin-LI and the vasoconstrictor effects. During the infusion 92, 82 and 76% of arterial endothelin-LI was removed by the kidney, spleen and hindlimb, respectively, whereas there was no clearance over the lung or degradation in plasma. After the infusion, arterial endothelin-LI decreased with a half life of 77 s, while the renal and splenic vasoconstriction persisted for 60 min. Characterization by reversed phase HPLC revealed that endothelin-LI in plasma and tissue co-eluted with synthetic endothelin. It is concluded that endothelin has tissue specific distribution, clearance and vascular effects in the pig.