Characterization of the carboxyl terminal flanking peptide of rat progastrin

A peptide identical in structure to the carboxyl-terminal flanking nonapeptide of rat progastrin, predicted by cDNA sequence, was synthesized. The synthetic peptide was used for production of a rabbit antiserum. This antiserum was used to develop a radioimmunoassay specific for rat carboxyl terminal flanking peptide. This assay was used to monitor the purification of immunoreactivity from rat antral extracts. Gel permeation, anion exchange and reverse phase chromatography steps resulted in a single absorbance peak associated with the carboxyl terminal flanking peptide immunoreactivity. The purified peptide eluted in the same position as the synthetic peptide during all three types of chromatography. This material was shown to be identical in mass to Ser-Ala-Glu-Glu-Glu-Asp-Gln-Tyr-Asn, the predicted sequence of the carboxyl terminal nonapeptide of rat progastrin.

Multiple gastrin-releasing peptide gene-associated peptides are produced by a human small cell lung cancer line

Products of the gastrin-releasing peptide gene were isolated from culture medium supernatant of a small cell lung cancer line, NCI-H345, by several (high performance liquid chromatography) HPLC steps. The column eluates were monitored by immunoassay and absorbance profiles. Gastrin-releasing peptide was identified in HPLC eluates by a specific radioimmunoassay. Two carboxyl-terminal gastrin-releasing peptide gene-associated peptides were identified by a radioimmunoassay specific for their predicted carboxyl terminus. The amino termini of these two peptides were determined by microsequence analysis. The shorter peptide was revealed to be a fragment of the larger peptide. Expression of an alternate mRNA was shown by isolation and characterization of a novel tetradecapeptide. Amino acid analysis, microsequence analysis, and mass spectral analysis confirmed that the structure was Ser-Leu-Leu-Gln-Val-Leu-Asn-Val-Lys-Glu-Gly-Thr-Pro-Ser. This peptide represents the carboxyl terminus of a peptide resulting from alternate processing of gastrin releasing peptide mRNA. This mRNA contains a 19-base deletion, creating a frame shift. A radioiodinated synthetic analog of this peptide (Tyr-Leu-Val-Asp-Ser-Leu-Leu-Gln-Val-Leu-Asn-Val-Lys-Glu-Gly-Thr-Pro-Ser ) bound specifically to a small cell cancer line with high affinity, suggesting possible biological activity of the isolated peptide.

Involvement of substance P in noncholinergic excitation of rabbit colonic muscle

Neurokinins have been implicated as noncholinergic excitatory neurotransmitters in the mammalian gastrointestinal tract. To characterize the myogenic and neurogenic response of colonic muscle to neurokinins we studied the mechanical response of muscle strips from proximal and distal colon and the release of [3H]acetylcholine in response to substance P (SP), neurokinin A (NKA) and neurokinin B (NKB). All neurokinins caused a dose-dependent inotropic response. SP was 80 times more potent in distal compared with proximal longitudinal muscle. The rank order of potencies in proximal longitudinal muscle was NKA greater than SP = NKB and in distal muscle NKA = SP = NKB. Desensitization to SP or pretreatment with a SP antagonist inhibited the mechanical response to SP and the atropine-resistant inotropic off response to electrical stimulation. Only longitudinal muscle from distal colon had an atropine- and hexamethonium-sensitive inotropic component to SP. In contrast, all three peptides were equipotent in releasing [3H]acetylcholine from longitudinal muscle strips preincubated with [3H]choline. These results suggest the following: 1) SP is a potent agonist of rabbit colon with a proximal distal gradient in biological potency; 2) the myogenic response of the distal colon appears to be mediated through a NK-1 receptor; and 3) SP is a major mediator of the noncholinergic component of the off response in distal longitudinal muscle.

Identification of serotonin from rabbit upper stomach as a stimulant of in vitro gallbladder contraction

Using an in vitro rabbit gallbladder bioassay, the distribution and identification of bioactive substances in rabbit gastrointestinal tract were investigated. Comparison of the bioactivities of tissue extracts before and after cholecystokinin was removed by affinity chromatography demonstrated that the distributions of cholecystokinin and non-cholecystokinin substances were different. While cholecystokinin bioactivity per g of tissue was highest in the duodenum, non-cholecystokinin bioactivity was greatest in the upper stomach. The biochemical properties of the non-cholecystokinin substance in the upper stomach could not be distinguished from those of serotonin. These included molecular weights of 176, identical ultraviolet spectra, similar nuclear magnetic resonance spectra, and co-chromatography in HPLC. By weight, serotonin had 1/6th of the bioactivity of cholecystokinin octapeptide. We conclude that the principal gallbladder-contracting substance in rabbit upper stomach is serotonin.

Processing of mammalian preprogastrin-releasing peptide

The processing of preprogastrin-releasing peptide in mammalian tissues and in cultured cells takes place at discrete sites (Figure 6). Signal peptidase cleaves away the signal peptide from the amino terminus of gastrin-releasing peptide. An exopeptidase activity may remove dipeptides from the amino terminus. The amidation site (not shown in Fig. 6; see Fig. 2) has the same general sequence (Gly-Lys-Lys) seen for other amidated peptides. Cleavage after single basic residues yields gene-related products from Form I or II preproGRP. A unique non-basic cleavage yields a gene-related product from Form III preproGRP. The processing that occurs to form GRP, GRP, and GRP gene-related peptides is shown in Figure 7. ProGRP is cleaved by a series of enzymes to form GRP with an amidated carboxyl-terminal methionine (indicated by an asterisk in Fig. 7). GRP is cleaved to form the decapeptide GRP. The carboxyl-terminal flanking peptides of all three mRNA translation products are cleaved to form several gastrin-releasing peptide gene-related products. Knowledge of the processing of gastrin-releasing peptide and its gene-related products will allow synthesis of duplicates of the stored forms of these peptides, which can then be used for biological testing.

Chemical characterization of rat cholecystokinin-58

Cholecystokinin-58 (CCK-58) was purified from rat intestines using an extraction method that yields large amounts of this peptide. Greater than 30% of total CCK immunoreactivity eluted before CCK-39 upon gel permeation chromatography (Sephadex G-50) if extracts were loaded onto Sep Pak cartridges before freezing. If the extracts were frozen and stored at -70 degrees C for six weeks, only 20% of the material eluted in this region and total immunoreactivity was reduced by 50%, suggesting that proteases were active under these storage conditions. This early eluting peak was purified by reverse phase and ion-exchange HPLC to a single absorbance peak. Microsequence analysis of this peak detected AVLRPDSEP which is the amino terminus of rat CCK-58 predicted from the rat preprocholecystokinin cDNA. Because degradation of CCK-58 occurred in these extracts, it is possible that CCK-58 is the predominant molecule form in the rat small intestine.

Plasma very low density lipoproteins contain a single molecule of apolipoprotein B

Rat and human very low density lipoproteins (VLDL) were fractionated by zonal ultracentrifugation, yielding sharply defined fractions with narrow sedimentation limits. Sedimentation coefficients for the individual fractions were determined at two densities with the analytical ultracentrifuge, and the results were analyzed to yield buoyant densities and molecular weights for the particles in each fraction. For the rat lipoproteins, the weight concentrations of triglycerides, cholesterol, phospholipid, and protein were determined for each fraction, and their molar concentrations of apolipoprotein B were measured with a radioimmunoassay. For the human lipoproteins the corresponding values were taken from Patsch et al. (Patsch, W., J. R. Patsch, G. M. Kostner, S. Sailer, and H. Braunsteiner. 1978. Isolation of subfractions of human very low density lipoproteins by zonal ultracentrifugation. J. Biol. Chem. 253:4911-4915). From these data, a ratio of the number of apoB peptides to the number of lipoprotein particles was calculated for each fraction. This ratio was close to 1 for all VLDL fractions, ranging in particle diameter from about 40 to 80 mm and 30 to 50 mm, respectively, for rat and human VLDL. The majority rat VLDL contain B-48 rather than B-100 as their (single) apoB peptide. Based on these data, we proposed that only a single copy of B-48 is required for VLDL assembly in rat liver, unless nascent hepatic VLDL contain additional apoB peptides which are uniformly lost from the plasma VLDL particles when they are analyzed.

An amino-terminal fragment of cholecystokinin-58 is present in the gut: evidence for a similar processing site of procholecystokinin in canine gut and brain

Radioimmunoassays using antibodies specific for the carboxyl terminus of cholecystokinin (CCK) and the midportion of CCK-58 (raised against synthetic canine CCK-33-(1-27] revealed the existence of a CCK fragment in canine gut and brain extracts which lacks the biologically active carboxyl terminal immunoreactivity. This material eluted on Sephadex G-50 gel permeation chromatography in the region of CCK-58, on high-pressure liquid chromatography (HPLC) after CCK-39 and before CCK-58, and on cation-exchange FPLC it eluted after CCK-58. The immunoreactive pattern, the ratio of absorbance at 280-220 nm and the chromatographic elution positions suggest that this large CCK-like molecule represents an amino-terminal fragment of CCK-58. This fragment is present in canine gut and brain. Therefore, a similar processing site of procholecystokinin is suggested in both tissues.

Solid phase synthesis and characterization of two canine gut gastrin-releasing peptides

Two canine gastrin-releasing peptides originally isolated from gut tissue extracts have been synthesized by solid phase methodology and purified by preparative reverse phase high performance liquid chromatography (RP-HPLC). The synthetic gastrin-releasing peptides GRP1-27 and GRP 5-27 were characterized with regard to homogeneity and composition using nine different RP-HPLC systems, mass spectroscopy, amino acid analysis, Edman degradation, methionine oxidation, and peptide mapping with tryptic, Staph. aureus V8 protease and cyanogen bromide cleavage (the latter two systems performed only with GRP 1-27). Although a scarcity of the natural products prevented quantitative biological comparison of the synthetic and natural peptides, they were found to elute identically on RP-HPLC co-chromatography and similar dose dependent biological potencies were observed in canine antral muscle tissue contraction experiments. Indeed, all the peptides containing the bombesin-like carboxyl terminal decapeptide sequence studied to date have similar biological activities.

Isolation and characterization of rabbit gastrin

The heptadecapeptide form the rabbit gastrin was extracted from 16 rabbit antra and purified by a combination of DEAE Sephadex, C-18 SEP PAK cartridges, fast performance liquid chromatography (FPLC) and reverse phase high pressure liquid chromatography (HPLC) steps. After the HPLC purification, a sharp, single peak of gastrin-like immunoreactivity was detected that had the same absorption to immunoreactivity ratio as human gastrin. An amino terminal pyrrolidone carboxylic acid blocking group was removed by incubation with pyrrolidone carboxylic peptidase. The amino acid analysis, microsequence analysis and mass spectrometry all confirmed the structure of rabbit gastrin being pQGPWLQEEEEAYGWMDFamide. This sequence is identical to human gastrin-17 except for glutamine in position 6 which replaces glutamate in human gastrin. Both sulfated and unsulfated rabbit gastrin-17 were characterized by mass spectrometry.

Biological activity of oxidized and reduced iodinated bombesins

A method is reported for preparing oxidized and reduced iodinated Tyr4-bombesin. Iodogen was used to iodinate Tyr4-bombesin and the reaction products were separated by reverse-phase HPLC. The peak of oxidized label was then reduced by incubation with 725 mM dithiothreitol at 80 degrees C (pH 8.0) for one hour and the reaction products separated by HPLC as before. The reduced but not oxidized peaks of 125I-Tyr4-bombesin stimulated amylase release from rat pancreatic acini in vitro. We conclude that oxidation of bombesin producing C-terminal methionine sulfoxide destroys the biological activity of the peptide and that this form of oxidation can be reversed.

Autocrine growth of murine lymphoma cells

By using an assay system in which small numbers of murine T lymphoma cells are stimulated to grow in serum-free medium, we have continued and expanded our previous studies of an autocrine growth factor that we call leukemia-derived growth factor (LDGF). We show that a T lymphoma cell line of immature phenotype, adapted to growth in serum-free medium, produces and responds to LDGF. LDGF activity is distinct from activities of 10 highly purified or recombinant hematopoietic growth factors including IL-1 and IL-2. However, growth-stimulating activity for the murine lymphoma cells is provided by a partially purified human LDGF.

Detection of cholecystokinin-58 in human blood by inhibition of degradation

Although cholecystokinin-58 (CCK-58) is a major molecular form stored in the intestine, it has not yet been shown to be released into the circulation. This report describes in vitro degradation of CCK-58 in human blood and plasma and the molecular forms detected when this degradation is inhibited. After incubation of CCK-58 for 150 min between 20 and 24 degrees C, approximately 60% of immunoreactivity recovered was degraded to smaller immunoreactive forms. Storage of the 150-min incubate at -20 degrees C for 3 days greatly increased the observed degradation to 85%. When CCK-58 was added in vitro to blood, similar degradation occurred. Degradation of CCK-58 could be inhibited by addition of acid. Blood was obtained 1 h after a test meal designed to stimulate CCK release. The pH was lowered during collection and processing of blood and plasma to inhibit in vitro degradation of cholecystokinin. This method permitted the detection of significant amounts of CCK-58 in circulation.

Distribution and characterization of calcitonin gene-related peptide immunoreactivity in the digestive system of normal and capsaicin-treated rats

The distribution and characterization of calcitonin gene-related peptide immunoreactivity in the digestive system of normal, capsaicin-treated, and littermate control rats were studied by radioimmunoassay, chromatography, and immunohistochemistry. The highest concentrations of calcitonin gene-related peptide immunoreactivity were found in the stomach (45 +/- 2.8 pmol/g wet wt, nonsecretory region; 38.7 +/- 4.4 pmol/g wet wt, secretory region) and rectum (30.9 +/- 1.6 pmol/g wet wt). Significant amounts of peptide were also found in the other regions of the gut and in the pancreas. Neonatal treatment with capsaicin, which causes a permanent degeneration of most of the small-diameter sensory neurons, reduced calcitonin gene-related peptide content by greater than 95% in the esophagus and stomach, by 60% in the pancreas, and by less than 50% in the intestine, when compared with littermate controls. Separation of extracts from the gut, pancreas, and brain by chromatography gave major peaks corresponding to the predicted rat calcitonin gene-related peptide and small unidentified peaks, which presumably arise from metabolism of the peptide. Immunohistochemical studies demonstrated that in the esophagus and stomach, calcitonin gene-related peptide immunoreactivity is restricted to nerve fibers, whereas in the intestine it is localized in both nerve fibers and enteric ganglion cells. In capsaicin-treated rats there was a virtually complete elimination of calcitonin gene-related peptide immunoreactive fibers innervating the esophagus and stomach, whereas in the small and large intestine there was a dramatic reduction and often a complete elimination of those associated with blood vessels and a slighter reduction of the nonvascular immunoreactive fibers. The results of this study indicate that calcitonin gene-related peptide immunoreactive nerve fibers innervating the rat digestive system originate from both intrinsic (enteric) and extrinsic (presumably sensory) sources and that both the intrinsic and extrinsic components appear to contain a substance that corresponds to the predicted calcitonin gene-related peptide.

Neurotensin-like immunoreactivity generated by pepsin from human plasma and gastric tissue

The present study demonstrates precursors of neurotensin-like immunoreactivity (NTLI) endogenous to human gastric tissue and plasma, and the existence of a gastric NTLI-generating enzyme system. The molecular size of the NTLI-precursors in plasma and gastric tissue were estimated by gel permeation chromatography to be ca 50,000-60,000 and 60,000-70,000 Da, respectively. The neurotensin-like peptide generated from the precursor was detected with a carboxyl-terminally directed antiserum but did not cross-react with an amino-terminally directed antiserum. A neurotensin-like peptide isolated from pepsin-treated human plasma was characterized by mass spectrometry and its amino acid sequence determined. This novel nonapeptide, referred to as kinetensin, failed to affect pentagastrin-stimulated acid secretion or blood pressure in the rat. Sequence homologies between neurotensin, kinetensin and proteins of the serum albumin family suggest a common evolutionary origin and raise questions regarding albumin-like proteins as precursors of regulatory peptides.

CCK-5: sequence analysis of a small cholecystokinin from canine brain and intestine

The purpose of this study is to purify and to characterize chemically cholecystokinin (CCK)-like peptides present in brain and gut extracts that elute from gel filtration after the octapeptide. Canine small intestinal mucosa and brain were boiled in water and then extracted in cold trifluoroacetic acid, and cholecystokinin-like immunoreactivity was determined by carboxyl-terminal specific radioimmunoassay. Gel permeation chromatography on Sephadex G-50 revealed a form of CCK apparently smaller than CCK-8. This peptide was purified by immunoaffinity chromatography and three successive reverse phase high-performance liquid chromatography steps. Microsequence analysis showed that the amino terminal primary sequence of this small CCK was Gly-Trp-Met-Asp. Immunochemical and chromatographic analysis indicated that the carboxyl-terminal residue was Phe-NH2 and thus the full sequence is Gly-Trp-Met-Asp-Phe-NH2. An antibody that recognizes synthetic CCK-8, CCK-5, and CCK-4 equally did not reveal the presence of significant amounts of CCK-4. These results indicate that CCK-5 is the major CCK form smaller than the octapeptide present in brain (19% of total CCK immunoreactivity) and small intestine (7% of total). This finding, coupled with the demonstration by others that CCK-5 interacts with high-affinity brain CCK receptors, indicates that CCK-5 may play a physiological role in brain function.

Cholecystokinin-58 is the major circulating form of cholecystokinin in canine blood

Cholecystokinin-58 (CCK-58) is the largest and most abundant, biologically active form of cholecystokinin in canine intestinal mucosa. Despite the high amounts in mucosa, CCK-58 has not been detected in significant amounts in the circulation. The release of CCK-58 into the peripheral blood in response to an intraduodenal perfusion of sodium oleate (9.0 mmol h-1) was studied in seven conscious dogs. Plasma (50 ml) was obtained before and after endogenous stimulation by a newly developed method that prevents in vitro degradation of large cholecystokinins. The relative abundance of immunoreactive forms of CCK was studied by high pressure liquid chromatography (HPLC) which separated the gastrin and CCK forms. Column eluates were measured with an antibody which recognizes the intact carboxyl terminus of both gastrin and CCK. Cholecystokinin immunoreactivity increased over basal in plasma by 7 fmol/ml after intraduodenal perfusion with sodium oleate. The most abundant form of stimulated cholecystokinin immunoreactivity eluted on HPLC in the position of CCK-58 (63% of total immunoreactivity found). Since CCK-58 is biologically active and is the most abundant circulating form, it should play an important role in the physiology of cholecystokinin.

Evidence for thyrotropin-releasing hormone (TRH) biosynthesis in rat prostate

TRH occurs in very high concentration in rat prostate. A species specific protein with repetitive -Gln-His-Pro-Gly- sequences, which are flanked on the N- and C-terminus by paired basic residues, has been shown to be the source of TRH in frog skin and rat hypothalamus. Following cleavage by trypsin-like enzymes, the peptide fragments with N-terminal Gln spontaneously cyclize to pGlu while Gly within the C-terminally extended peptides serves as the -NH2 donor for the alpha-amidation of the proline residue. Because this last step in the biosynthesis of TRH is rate limiting for pGlu-His-Pro-Gly, we have combined several chromatographic and radioimmunoassay techniques to identify this TRH precursor in rat prostate.

New molecular forms of cholecystokinin. Microsequence analysis of forms previously characterized by chromatographic methods

Cholecystokinin previously has been characterized by chromatographic and immunological techniques. Analysis of cDNA has revealed the structure of preprocholecystokinin. The predicted processing sites of preprocholecystokinin cannot account for the multiple forms of cholecystokinin detected. This report details the isolation and characterization of cholecystokinin peptides containing 58, 39, 33, 25, 18, 8, 7, and 5 amino acids. None of the cleavages that occurred to form these peptides was at the carboxyl side of double basic residues. Cholecystokinin 25, 18, and 7 have not previously been isolated and identified by sequence analysis. The processing that forms these peptides includes cleavage after single basic residues for the 58, 39, 33, and 8 amino acid peptides. The 25, 18, 7, and 5 amino acid peptides must be formed by other endopeptidases or combinations of endo- and exopeptidases. The analysis of this series of peptides provides the chemical basis for structural differences in cholecystokinin molecules previously demonstrated by chromatographic and immunological methods. These structures provide insight into tissue-specific processing that occurs for this important regulatory peptide in intestine and brain.

Cholecystokinin--gene structure, and molecular forms in tissue and blood

The gene structure of human cholecystokinin (CCK) is known and the cDNA structures are known for pig and rat. However, the molecular forms of CCK produced, stored and released from neural or endocrine cells cannot be predicted from the known structures of preprocholecystokinin derived from cDNA. It is well recognized that gastrin and CCK share carboxyl-terminal homology and similar processing to form the biologic active peptides. Comparisons of the structures of preprogastrin and preprocholecystokinin reveal a similar degree of homology in the midregion of the precursors (the structure of preprogastrin 55-59 and preprocholecystokinin 39-42 is His-Arg-Arg-Gln-Leu). Gastrin-34 (whose amino terminus corresponds to position 58 of preprogastrin) is formed by cyclization of glutamine to pyrrolidone carboxylic acid subsequent to cleavage at the double basis site. Identical posttranslational processing in this region would yield CCK-61. However, CCK-58 is the largest biologically active peptide so far isolated and chemically characterized. CCK can be found in high concentrations in gut and brain but the molecular forms differ in the two tissues. Thus, the most abundant forms in the intestine are CCK-58, followed by CCK-39, CCK-33, and CCK-8, whereas in the brain CCK-8 is the most abundant form, followed by CCK-58 and CCK-5. The brain contains in contrast to the intestine little or no CCK-39 and CCK-33. Therefore differences in posttranslational processing between gut and brain are assumed. The predominant small CCK forms in the brain act presumably as neurotransmitters. Large and small molecular forms are released from the endocrine cell of the gut and act as circulating hormones. Several problems have hindered the characterization and quantitation of CCK forms in tissue and blood. The large forms (CCK-58, CCK-39, CCK-33) are easily lost because they are more basic and bind to glass and plastic surfaces. In addition to recovery problems, CCK-58 can be readily degraded into smaller forms at neutral or basic pH in tissue extracts and in blood or plasma. When special care is taken to prevent these problems, we have shown that, in the dog, CCK-58 is not only the most abundant molecular form in the intestinal mucosa but also in the circulating blood. The physiology and pathophysiology of circulating CCK (regulation of pancreatic secretion, of the motility of the gallbladder and the bowel, and involvement in satiety mechanisms) has to be studied further.

Relative bioactivities of cholecystokinins-8 and -33 on rat pancreatic acini

The relative potencies of cholecystokinin (CCK-33) and its carboxyl terminal octapeptide (CCK-8) for stimulation of amylase release from rat pancreatic acini was measured. Porcine CCK-33 and synthetic CCK-8 were initially subjected to high pressure liquid chromatography to assess purity. Concentrations of each peptide were determined by amino acid analysis. The relative immunoreactivities of CCK-33 and CCK-8 were compared using an antibody that recognizes the common carboxyl terminus of these forms. This antibody bound CCK-8 and CCK-33 with nearly equal affinity. The relative potencies of CCK-33 and CCK-8 were then measured by comparing their abilities to stimulate amylase release from isolated rat pancreatic acini. Statistical analysis of the relative potencies of the two hormones indicated that CCK-8 was 36% more potent than CCK-33 in this assay system. These data suggest that differences in biological activities between large and small forms of CCK are not as great as previously reported.

Isolation and characterization of a neurotensin-like decapeptide from a canine upper small intestinal extract

Neurotensin-like immunoreactivity can be detected in extracts of canine upper gastrointestinal mucosa when measured by carboxyl terminal but not by amino terminal antibodies to neurotensin. The nature of this immunoreactive material was characterized by complete purification on gel filtration and HPLC followed by peptide microsequence analysis. The structure obtained was Glu-Asn-Lys-Pro-Arg-Arg-Pro-Tyr-Ile-(Leu), identical in structure to the carboxyl terminal decapeptide of neurotensin. It cannot, however, be excluded that this neurotensin decapeptide was generated from a larger neurotensin-like peptide during the extraction procedure by a physiological or artificial enzymatic process. Since carboxyl terminal neurotensin fragments containing eight or more residues have full biological activity, this peptide may be responsible for neurotensin-like biological activities within the mucosa of, or after release from, the upper gut.

Homology of lipoprotein lipase to pancreatic lipase

Bovine milk lipoprotein lipase was subjected to amino acid sequence analysis. The first 19 amino-terminal residues were Asp-Arg-Ile-Thr-Gly-Gly-Lys-Asp-Phe-Arg-Asp-Ile-Glu-Ser-Lys-Phe-Ala-Leu- Arg. In addition, reversed-phase high-performance liquid chromatography of a tryptic digest of reduced and alkylated lipase resolved a number of peptides, five of which contained cysteine. Sequence analysis of the tryptic peptides revealed in most instances a close homology to porcine pancreatic lipase. Based on this homology, the relative alignment of the sequenced lipoprotein lipase peptides can be made. In addition, a potential binding site for the triacylglycerol substrate and a carbohydrate-binding domain for lipoprotein lipase are postulated.

The amino acid sequence of kinetensin, a novel peptide isolated from pepsin-treated human plasma: homology with human serum albumin, neurotensin and angiotensin

A novel nonapeptide with neurotensin-like immunoreactivity was isolated from pepsin-treated human plasma by dialysis, ion-exchange chromatography and high performance reversed-phase liquid chromatography. The amino acid sequence was determined by automated gas-phase sequence analysis as Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-Leu. Sequence homology with human serum albumin and with the biologically active peptides neurotensin and angiotensin is demonstrated. The name proposed for this peptide is kinetensin.

Potency of natural and synthetic canine gastrin-releasing decapeptide on canine antral muscle

The carboxyl terminal decapeptide of gastrin-releasing peptide (GRP-10), a small, naturally occurring bombesin-like peptide, has been isolated from canine antral muscle, synthesized, and its bioactivity compared with other synthetic and natural gastrin-releasing peptides on stimulation of spontaneously occurring contractions of canine circular antral muscle in vitro. Concentrations of peptides were verified by amino acid analysis and radioimmunoassay. In this system three forms of natural canine GRP, synthetic GRP-10, synthetic porcine gastrin-releasing heptacosapeptide (GRP-27), [Gln3]GRP-10, and [Arg3]GRP-10 all were similar in potency to synthetic amphibian bombesin. These results differ from the low activity of GRP-10 previously reported in rat brain. The full biological potency on canine antral motility and the presence of GRP-10 in nerve fibers in the gut and in the spinal cord suggest a possible role for this peptide as a neurotransmitter or neuromodulator in regulation of smooth muscle contraction.

Partial purification of a novel stimulant of gastric acid secretion from canine non-antral mucosa

A novel stimulant of gastric acid secretion was extracted and purified from the non-antral gastric mucosa of the canine stomach and some of its biological properties were examined. Tissue was boiled in water and extracted in 2% trifluoroacetic acid. The stimulatory activity was purified by a combination of reverse-phase high pressure liquid chromatography (HPLC) and gel filtration. Fractions were assayed for a stimulation of basal, pentagastrin- and histamine-stimulated gastric acid secretion in the anaesthetized rat. Stimulatory activity was eluted from reverse-phase HPLC columns with acetonitrile and its elution from Sephadex G-10 and G-50 columns suggested a molecular weight of 1,000 to 3,000. The highly purified extracts enhanced basal, pentagastrin- and histamine-stimulated acid secretion in the rat. A stimulatory fraction was purified which was devoid of immunoreactive gastrin and gastrin-releasing peptide and contained only small amounts of histamine. Its chromatographic properties differed from those of histamine and acetylcholine. On two occasions the stimulant was purified to homogeneity and found to contain amino acids. Insufficient pure material was obtained for full characterization. The stimulant has been tentatively called oxyntin.

Purification of somatostatin from frog brain: coisolation with retinal somatostatin-like immunoreactivity

Somatostatin-like immunoreactivity (SLI) was purified from frog brain and retina, and the structure of the brain peptide was determined. Frog brain (101 g) and retinal (45 g) tissues were extracted with 3% acetic acid, yielding 9.6 and 0.44 nmol of SLI, respectively. SLI was further purified by chromatography on a somatostatin immunoaffinity column followed by sequential application to reverse-phase C-18 HPLC columns. The brain and retinal peptides, purified roughly 100,000-fold with net yields of 7.5 and 2.3%, respectively, appeared identical in the final steps of purification. The amino acid sequence of brain SLI, as determined by a gas-phase automated Edman degradation technique, was as follows: Ala-Gly-(Cys)-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-(Cys). Our data indicate that despite structural variations in somatostatins of other lower vertebrates, the amino acid sequence of frog brain and, by deduction, retinal SLI is identical to that of somatostatin tetradecapeptide. These findings support the physiological relevance of studies directed at elucidating the neurotransmitter function of somatostatin using the well-established models of frog brain and retina.

In vitro production of a TRH-homologous peptide and His-Pro diketopiperazine by human semen

Fresh human semen, diluted 1:1 v/v with 0.15 M NaCl- 0.05 M phosphate, pH 7.5, undergoes a 3-fold increase in total thyrotropin-releasing hormone (TRH) immunoreactivity on incubation at 4 C for 8 to 16 hours. To identify the mechanism for this increase, pooled human semen was incubated at 4, 37, and 60 C, and the change in composition of the immunoreactive TRH peptides was quantitated by high pressure liquid chromatography and radioimmunoassay of TRH. His-Pro diketopiperazine, a biologically active metabolite of TRH consisting of a cyclic dipeptide of histidine and proline, also was measured by specific RIA. The concentration of TRH (pGlu-His-Pro-NH2) dropped precipitously within the first hour after dilution and incubation at all temperatures studied. A hydrophobic TRH-homologous peptide with the amino acid composition (Glu,X,Y,Pro), where X and Y are neutral, nonaromatic amino acids, increased 8-fold during 16 hours of incubation at 4 C. This TRH-homologous peptide is not derived from TRH because it lacks the histidine is not derived from TRH because it lacks the histidine residue. A 3- to 23-fold increase in His-Pro diketopiperazine levels occurred after 4 hours at 37 C. This was not due primarily to enzymatic removal of the pyroglutamyl residue from TRH by pyroglutamate aminopeptidase, since about 1 hour after ejaculation the initial His-Pro diketopiperazine levels were 9.7 +/- 5.1 micrograms/ml, or approximately 1000-fold greater than the corresponding levels of seminal TRH. Because cycloheximide, which blocks ribosomal protein biosynthesis, did not inhibit in vitro production of the TRH-homologous peptide and the His-Pro cyclic dipeptide, these peptides, like TRH, most likely arise from post-translational cleavage and processing from pre-existing macromolecular precursor proteins.

Canine bombesin-like gastrin releasing peptides stimulate gastrin release and acid secretion in the dog

The synthetic mammalian bombesin-like peptides, canine gastrin releasing peptide 27, 23 and 10, and porcine gastrin releasing peptide 27 were compared with amphibian bombesin 14 and 10 during intravenous infusions into six conscious dogs with chronic gastric cannulae. Gastrin and gastrin releasing peptide were measured in peripherally sampled venous blood by radioimmunoassay and gastric acid secretions were collected. All forms of gastrin releasing peptide stimulated gastrin release and gastric acid secretion in a dose-dependent manner. The larger canine and porcine peptides were more potent than the decapeptide. Bombesin 14 was more potent than bombesin 10. A rise in the venous concentration of immunoreactive gastrin releasing peptide of only 20 fmol ml-1 stimulated gastrin release to about 50% of maximal. Gastrin releasing peptide 10 was cleared from the circulation three times faster than the larger forms and this may account for the apparent differences in potency.

Isolation and partial characterization of canine epidermal growth factor/urogastrone

Canine epidermal growth factor (EGF)/urogastrone was partially purified from dog urine by fractional precipitation with (NH4)2SO4, ion-exchange chromatography with DEAE-cellulose DE-52, gel filtration with Sephadex G-50, and a second DE-52 chromatography, to yield receptor-competing activity equivalent to 13 micrograms of standard mouse EGF/litre of starting urine. The purification was monitored by a competitive radioreceptor assay using fixed monolayers of A431 cells. The partially purified canine EGF/urogastrone demonstrated a growth-stimulating activity in 3T3 mouse fibroblast cells as potent as mouse EGF. Analysis by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed one major peptide component with an Mr similar to that of mouse EGF, and two minor peptides of slightly higher Mr. The major peptide component was isolated after reduction and its amino acid composition was determined.

Rapid high-yield purification of canine intestinal motilin and its complete sequence determination

Canine motilin has been purified from small amounts of canine intestine in a form suitable for microsequence analysis. The sequence determined is: Phe-Val-Pro-Ile-Phe-Thr-His-Ser-Glu-Leu-Gln-Lys-Ile-Arg-Glu-Lys-Glu-Arg- Asn-Lys - Ile-Arg-Asn-Lys-Gly-Gln. Canine motilin differs from porcine motilin at five positions. The rapid, high-yield (24% overall yield) microisolation techniques used for canine motilin should be suitable for the isolation of other basic peptides found in low levels in tissue that is available only in limited amounts. These methods should make the isolation and sequence determination of human brain and gut peptides more readily achievable.

Catabolism of gastrin releasing peptide and substance P by gastric membrane-bound peptidases

The catabolism of two gastric neuropeptides, the C-terminal decapeptide of gastrin releasing peptide-27 (GRP10) and substance P (SP), by membrane-bound peptidases of the porcine gastric corpus and by porcine endopeptidase-24.11 ("enkephalinase") has been investigated. GRP10 was catabolized by gastric muscle peptidases (specific activity 1.8 nmol min-1 mg-1 protein) by hydrolysis of the His8-Leu9 bond and catabolism was inhibited by phosphoramidon (I50 approx. 10(-8) M), a specific inhibitor of endopeptidase-24.11. The same bond in GRP10 was cleaved by purified endopeptidase-24.11, and hydrolysis was equally sensitive to inhibition by phosphoramidon. SP was catabolized by gastric muscle peptidases (specific activity 1.7 nmol min-1 mg-1 protein) by hydrolysis of the Gln6-Phe7, Phe7-Phe8 and Gly9-Leu10 bonds, which is identical to the cleavage of SP by purified endopeptidase-24.11. The C-terminal cleavage of GRP10 and SP would inactivate the peptides. It is concluded that a membrane-bound peptidase in the stomach wall catabolizes and inactivates GRP10 and SP and that, in its specificity and sensitivity to phosphoramidon, this peptidase resembles endopeptidase-24.11.

Mammalian bombesin-like peptides: neuromodulators of gastric function and autocrine regulators of lung cancer growth

Peptides corresponding closely in structure to the biologically active carboxyl terminal region of the amphibian peptide bombesin have now been isolated from several mammalian species, including man. Two principal forms have been found: one contains 27 amino acids and exhibits variations in amino acid sequence in the amino terminal region; the other is the carboxyl terminal decapeptide and probably does not vary among mammals. These peptides exhibit full immunoreactivity with most bombesin antisera and account for "bombesin-like immunoreactivity" that has been described in mammalian brain, sympathetic ganglia, and nerve fibers in the gut as well as in fetal lung endocrine cells and certain lung tumors, especially small cell lung carcinoma. The name gastrin releasing peptide (GRP) was given to the porcine and avian heptacosapeptides by McDonald and Mutt. The larger and smaller mammalian peptides now often are called GRP27 and GRP10. Both forms exhibit the full spectrum of activity shown by bombesin. Evidence has been obtained that neural release of mammalian bombesin-like peptides is physiologically important in regulation of gastrin release from the stomach. Lung tumors that produce bombesin-like peptides also have receptors for bombesin. These receptors appear to be involved in the autocrine regulation of tumor cell proliferation.

The isolation and sequence analysis of vasoactive intestinal peptide from a ganglioneuroblastoma

A ganglioneuroblastoma was excised at surgery from a 1-yr-old girl with severe watery diarrhea. The tumor, weighing 1 g, was extracted in trifluoracetic acid and contained 8.3 nmol immunoreactive vasoactive intestinal peptide. The peptide was isolated by affinity chromatography and high pressure liquid chromatography and was found to be identical to porcine vasoactive intestinal peptide by amino acid analysis and microsequence analysis.

Isolation of a large cholecystokinin precursor from canine brain

Cholecystokinin (CCK)-like immunoreactivity (CCK-LI) in a pool of 12 dog brains was extracted sequentially into boiling water and cold 2% trifluoroacetic acid. Gel filtration on Sephadex G-50 revealed three main molecular forms detected by a carboxyl-terminal antibody; one was eluted in the position of CCK-58 (58 amino acid residues long); a second, in the position of CCK-8; and a third, near the radioactive iodide marker. When the CCK-LI was purified by affinity chromatography using carboxyl-terminal CCK antibody followed by three steps of reversed-phase high-pressure liquid chromatography, three components were isolated and characterized by sequence microanalysis. The smallest component was the pentapeptide common to gastrin and CCK. The second peak was eluted in the same region as synthetic CCK octapeptide, and sequence analysis showed that the chemical structure of this biologically active region of canine CCK is identical to that found in sheep and pig brains. The 22-residue amino-terminal sequence of brain CCK-58 was: Ala-Val-Gln-Lys-Val-Asp-Gly-Glu-Pro-Arg-Ala-His-Leu-Gly -Ala-Leu-leu-Ala-Arg-Tyr-Ile-Gln-, the same as the sequence found for canine intestinal CCK-58 from this pool of dogs. This is the same sequence others have reported for porcine brain CCK-58 lacking nine amino acid residues (CCK-58 desnonapeptide) except that the porcine peptide had a serine in position 9. The canine CCK amino-terminal sequence differed from the sequence Ala-Gln-Lys-Val-Asn-Ser previously reported for intestinal CCK-58 purified from another pool of dog tissue, but the rest of the residues identified were identical in the two peptides. CCK-58 may be a molecular precursor of the smaller forms of CCK in brain as well as in gut.

Amino terminal fragments of human progastrin from gastrinoma

Two peptides which copurified from a human gastrinoma were found to correspond to the amino acid sequence deduced for the amino terminal portion of human and porcine progastrin. The sequence of peptide A is Ser-Trp-Lys-Pro-Arg-Ser-Gln-Gln-Pro-Asp-Ala-Pro-Leu-Gly-Thr-Gly-Ala-Asn- Arg-Asp-Leu-Glu-Leu which is identical to an amino terminal portion of human progastrin. The sequence of peptide. B is identical to that of peptide A except it is missing the first five amino acids. If peptide A corresponds to the amino terminus of progastrin, the signal peptidase cleaves at an Ala-Ser bond.

Isolation and characterization of biologically active and inactive cholecystokinin-octapeptides from human brain

Cholecystokinin-like immunoreactivity (CCK-LI) in 0.9 kg human brain was extracted by 2% trifluoroacetic acid at 4 degrees C. Sephadex G50 gel filtration of crude extract revealed one main molecular form of CCK, detected by a carboxy-terminal antibody (5135), that eluted in the position of CCK8. When the CCK-LI in the extract was purified by affinity chromatography using another carboxyl-terminal CCK antibody followed by several steps of reverse phase high pressure liquid chromatography (HPLC), a component was isolated that was found by sequence analysis to be identical to the carboxyl-terminal CCK-octapeptide of porcine CCK33, isolated from intestinal mucosa, and to CCK-octapeptide, isolated from sheep brain. This component possessed comparable biological potencies to synthetic sulfated CCK8 in eliciting amylase release and in competitively displacing radioiodinated CCK33 from isolated mouse pancreatic acini. Furthermore, it exhibited a similar binding characteristic to CCK8 in binding to specific receptors on mouse brain cortical particulate preparations. On high pressure liquid chromatography another minor, earlier eluting immunoreactive peak was observed, which had the same amino acid composition and sequence as CCK8. These findings suggested that this material was oxidized CCK8. This earlier eluting component, exhibiting CCK8-like immunoreactivity, did not induce amylase release from acini and had no or minimal effect in inhibiting tracer CCK33 binding to receptors on isolated acini or on mouse brain cortical particulate preparations at the concentrations tested.

Isolation and sequence analysis of human bombesin-like peptides

The decapeptide form of human gastrin releasing peptide was isolated from acid extracts of liver tissue containing a metastatic human bronchial carcinoid tumor. A larger form also was isolated and partially characterized. During gel permeation chromatography the major immunoreactive peak eluted in the same region as synthetic gastrin releasing decapeptide while a second minor immunoreactive peak eluted near gastrin releasing peptide. Bombesin-like immunoreactivity (BLI) was purified by successive applications to reverse phase high pressure liquid chromatography (HPLC) columns. After four successive HPLC purifications a single peak of bombesin-like immunoreactivity was detected. Amino acid analysis, microsequence analysis and coelution with synthetic peptide indicated that the predominant form present in metastatic tumor tissue was identical to the decapeptide form of canine gastrin-releasing peptide. The less abundant form was purified by cation exchange chromatography followed by reverse phase high pressure liquid chromatography. Partial microsequence analysis of this peptide, through the first 11 residues, was Val-Pro-Leu-Pro-Ala-Gly-Gly-Gly-Thr-Val-Leu. This sequence differed from that of hog heptacosapeptide gastrin releasing peptide at positions 1,3,4 and 5 and from the canine peptide as positions 1,3,5, and 7.

Catabolism of neurotensin in interstitial fluid of the rat stomach

The catabolism of neurotensin (NT) was studied in the gastric submucosa of the conscious rat using a novel technique to obtain a dialysate of interstitial fluid. A microdialysis fiber system was surgically implanted into the gastric submucosa, and 2 days later experiments were commenced on conscious animals. Isotope-labeled NT was administered to the tissue, and a dialysate of the submucosal interstitial fluid was collected. In the dialysate, NT and catabolites of NT formed in the interstitial fluid were identified and quantitated by high-pressure liquid chromatography. The catabolism of 125I-NT-(1-13) and [3H]NT-(1-13) was studied as was the further breakdown of the major catabolites. NT-(1-13) was, regardless of the type of label, catabolized mainly into NT-(1-8), NT-(9-13), NT-(1-11), and free tyrosine. None of the catabolites formed is known to possess significant biological activity. NT-(9-13) was rapidly cleared, whereas the amino-terminal fragments NT-(1-8) and NT-(1-11) were more resistant to degradation. The biological half-life of neurotensin in the gastric submucosa of the rat was between 9 and 15 min.

Pancreatic polypeptide from rat pancreas

Pancreatic polypeptide (PP) has been isolated from rat pancreas by gel filtration, ion exchange chromatography, and high performance liquid chromatography. The isolation was monitored with a RIA, using antibody to the carboxyl-terminal hexapeptide of bovine PP. Rat PP contains 36 amino acids and is similar in composition to PP from other mammalian sources. The single methionine residue in the peptide appears to oxidize easily to the sulfoxide, thereby giving rise to two immunoactive peaks on high performance liquid chromatography. Reduction to the native peptide can be accomplished with mercaptoethanol. The PP content of rat pancreas is about 2 mg/kg. The amino acid sequence of rat PP is Ala-Pro-Leu-Glu-Pro-Met-Tyr-Pro-Gly-Asp- Tyr-Ala-Thr-His-Glu-Gln-Arg-Ala-Gln-Tyr-Glu-Thr-Gln-Leu-Arg-Arg-Tyr-Ile- Asn-Thr-Leu-Thr-Arg-Pro-Arg-Tyr-NH2. This sequence preserves characteristics necessary for stabilization of the compact globular conformation found in avian PP.

Isolation and characterization of rat vasoactive intestinal peptide

We have used gel filtration, ion exchange chromatography, affinity chromatography and reversed-phase HPLC to isolate vasoactive intestinal peptide from rat intestine. Microsequence analysis of 1 nmole peptide indicated that the sequence was identical to the porcine octacosapeptide VIP. In radioimmunoassay with four antisera and in the turkey pancreas bioassay, rat VIP was equipotent with highly purified preparations of porcine, human and canine VIP. A less basic rat VIP-variant was also isolated and the N-terminal decapeptide region that was sequenced was identical with that of porcine VIP.

Catabolism of bombesin in the interstitial fluid of the rat stomach

The aim of this study was to develop a method to examine the catabolism of neuropeptides in the tissue fluids that bathe specific regions in the alimentary tract of the conscious animal. Two bundles of dialysis fibers were surgically implanted in the submucosal region of the gastric corpus in the anesthetized rat. After recovery from surgery, one set of fibers was perfused with 125I - Tyr4 bombesin 14. Some molecules of peptide diffused into the tissues and were catabolized by enzymes therein. The catabolites were collected in the second dialysis fiber and fractionated by high pressure liquid chromatography. Bombesin 14 was catabolized to iodo-tyrosine and three unidentified peptides. The catabolites did not bind with a carboxyl-terminal specific antiserum and, as this is the biologically active region of bombesin, were devoid of any biological activity.

A novel active pentapeptide from chicken brain identified by antibodies to FMRFamide

The tetrapeptide Phe-Met-Arg-Phe-NH2 (FMRFamide) and peptides structurally related to it, have been isolated from molluscan ganglia. They have widespread actions on both invertebrate and vertebrate tissues and there is increasing evidence that they are an important group of invertebrate peptide neurotransmitters. It is of interest that the primary amino acid sequence of FMRFamide forms the C-terminal tetrapeptide of an enkephalin-like heptapeptide (Met-enkephalin-ArgPhe) isolated from bovine adrenal medulla and striatum. Antisera to FMRFamide have been shown to react in radioimmunoassay and immunohistochemistry with material in the central nervous system of various vertebrate species, but the identity of this material, and in particular its relationship to the opioid heptapeptide, remains uncertain. We have used antibodies specific for the C-terminus of FMRFamide in radioimmunoassays to monitor purification of the material in chicken brain. We describe here the sequence of one of the peptides obtained. It is a biologically active peptide which does not seem to be related to other known vertebrate neuropeptides.

Structure of somatostatin isolated from bovine retina

Somatostatin-like immunoreactivity (SLI) from bovine retina was purified and its structure determined. Retinal tissue (1868 g) extracted with 3% acetic acid yielded 18.6 nmol SLI. This peptide was purified by chromatography on an affinity column made with anti-somatostatin antiserum, a reverse-phase C-18 HPLC column, and three sequential applications on a reverse-phase phenyl HPLC column. The peptide was purified 103,000-fold from the initial extract with an overall yield of 14.4%. Amino acid sequence determination by an automatic Edman degradation technique revealed the sequence to be as follows: Ser-Ala-Asn-Ser-Asn-Pro-Ala-Met- Ala-Pro-Arg-Glu-Arg-Lys-Ala-Gly-(Cys)-Lys- Asn-Phe-Phe-Trp-Lys-Thr-(Phe, Thr, Ser, Cys). The apparent identity of this peptide with somatostatin octacosapeptide (S28) purified from other mammalian tissue indicates the phylogenetic conservation of its structure and facilitates the use of the retina as a model system for studying the neurotransmitter function of somatostatin.

Biological activity of canine intestinal cholecystokinin-58

The biological activity of a recently characterized cholecystokinin molecule, canine CCK-58, has been tested using perifused canine gallbladder strips and isolated mouse pancreatic acini. It has been shown that canine CCK-58, purified by affinity chromatography and molecular sieve chromatography, is biologically as potent as canine CCK-39,33 (component II) and synthetic CCK-8. The biological responses were inhibited by dibutyryl cGMP, a known CCK antagonist. CCK-58 is one of the main large molecular forms of CCK in the intestine mucosa. Whether CCK-58 is only an intracellular precursor of other CCK molecules or an important circulating hormone cannot be determined from the data currently available.

Amino acid sequences of three bombesin-like peptides from canine intestine extracts

Amino acid sequences of three canine bombesin-like peptides were determined after sequential purification of an extract obtained from 820 g of intestinal muscle. These three peptides contained 27, 23, and 10 amino acid residues. The sequences of the two shorter forms were identical to the corresponding carboxyl-terminal sequence of the heptacosapeptide. The sequence of the largest peptide is H2N-Ala-Pro-Val-Pro-Gly-Gly-Gln-Gly-Thr-Val-Leu-Asp-Lys-Met-Tyr-Pro-Arg-Gly-Asn - His(Trp-Ala-Val-Gly-His-Leu-Met-CONH2). The sequence of the 23-residue peptide is H2N-Gly-Gly-Gln-Gly-Thr-Val-Leu-Asp-Lys-Met-Tyr-Pro-Arg-Gly-Asn-His-Trp-Ala- Val-Gly(His-Leu-Met-CONH2). The sequence of the decapeptide is: H2N-Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-CONH2. Comparison of the 27-residue peptide with the known structure of porcine gastrin-releasing peptide, another bombesin-like heptacosapeptide, reveals four amino acid substitutions: canine bombesin-like peptide had Pro 4, Gly 5, Gln 7, Asp 12, whereas porcine gastrin-releasing peptide had Ser 4, Val 5, Gly 7, Ala 12. Radioimmunoassay of brain extracts after similar purification revealed the presence of similar large and small forms of immunoreactive bombesin peptides, but with apparent tissue concentrations of about 4% of those present in intestinal muscle. Canine bombesin-like peptides represent another example of mammalian neuropeptides existing in more than one biologically active molecular form.