Sensitive method of detection, quantitation and purification of peptides using pre-column derivatization with phenyl isothiocyanate

A sensitive method for the detection, quantitation and purification of peptides is described. The method is based on pre-column derivatization of peptides with phenyl isothiocyanate to form phenylthiocarbamoyl derivatives (PTC peptides). The derivatized peptides are analysed by reversed-phase high-performance liquid chromatography on a Zorbax ODS column (5 micron) and detected at 269 nm with a sensitivity limit of 1-5 pmol. The technique was utilized for the separation of a mixture of closely related synthetic peptides. The eluted PTC peptides were collected with an average recovery yield of 75% as determined by amino acid analysis. This method of separation of PTC peptides was also combined with the determination of the complete structure of recovered PTC-dynorphin A-(1-13) using the solid-phase sequenator (Sequemat). The advantages of the derivatization method are the rapidity and completeness of the reaction, the stability of the product, the sensitivity and specificity of the detection of derivatized peptides and the compatibility of the technique with subsequent analytical procedures. A particular application of this method was exemplified by the dosage of enkephalins secreted from perfused bovine adrenal glands.

Functional opioid receptor sites in human placentas

We characterized the presence of opioid peptide receptor sites in plasma membranes and cells from human midterm and term placentas. Incubations with [3H]ethylketo-cyclazocine (EKC) at increasing doses revealed the presence of high affinity, low capacity, opioid peptide receptor-specific binding of the kappa-type. Scatchard analysis of the binding data showed, in the plasma membranes, linear plots at both stages of pregnancy with similar mean equilibrium association constants of 1.31 +/- 0.29 (+/- SE) X 10(9) mol/L-1 (n = 4) at midterm and 0.52 +/- 0.63 X 10(9) mol/L-1 at term (n = 4). In placental cells (n = 4) from term gestations, the binding plots were curvilinear; the first component had a Ka of 5.51 +/- 0.50 X 10(9) mol/L-1, and the second component had a Ka of 1.33 +/- 0.81 X 10(8) mol/L-1 (P less than 0.01). When standardized per mg tissue protein, the number of binding sites in plasma membranes increased from 13.8 +/- 9.8 fmol at midterm to 50.0 +/- 18.6 fmol at term (P less than 0.05). For term placental cells, the concentration of binding sites was 81.2 +/- 36.0 fmol for the high affinity sites and 713 +/- 390 fmol for the lower affinity sites. Specificity for the kappa-type of OPR was found based on the inability of mu- or delta-opioid peptides, as well as LHRH and TRH, to compete for [3H]EKC binding. Term placental cells incubated with various doses of opioid peptides had a 50% increase in placental lactogen production. The increase was significantly higher than controls only with kappa-agonists (P less than 0.05), maximal with 10(-9) mol/L EKC, and completely inhibited by 5 X 10(-6) mol/L naloxone. These results expand on previous data demonstrating the presence of opioid peptide receptor in placental plasma membranes and suggest a role for opioid peptides in regulating secretion of placental lactogen by placental cells.

Changes in autacoid and neuropeptide contents of lung cells in asbestos-induced pulmonary fibrosis

The purpose of this study was to determine if asbestos-induced pulmonary fibrosis in the rat can affect the levels of autacoids and peptides in freshly isolated lung cells. Lung fibrosis was experimentally induced in rats by a single intratracheal instillation of 5 mg UICC Canadian chrysotile B fibers. Isolated lung cells were prepared from normal and from asbestos-exposed rats. These cells were also fractionated on bovine serum albumin (BSA) gradients. The contents of serotonin (5-HT), histamine (HIST), vasoactive intestinal peptide (VIP), and bombesin (BN) were measured in isolated total cell preparations as well as in density-fractionated cell populations from normal and from asbestos-exposed rats. Analysis of total lung cell preparation showed the presence of heterogeneous populations in normal rat lung. After asbestos exposure, there were significant changes in these cell populations as evidenced by significant increases in lymphocyte and mast cell numbers. In addition, increased levels of 5-HT, HIST, and VIP were observed in isolated lung cells obtained from rats exposed to asbestos 1, 3, and 6 months after instillation. BN content was unchanged 3 months after treatment, but was significantly increased at the 6 month-interval, suggesting a different pattern of response for this neuropeptide. Density fractionation of various cell populations further showed selective changes in specific cell fractions of lung after asbestos exposure. At 6 months, increased levels of 5-HT, HIST, and VIP were associated with cell fraction 7, whereas changes in BN content were found in cell fractions 2 and 3. Similarly, there was a significant increase of mast cells in fraction 7 at the 6-month interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Asbestos-induced fibrosis in rats: increase in lung mast cells and autacoid contents

Adult male Wistar rats were treated with one tracheal instillation of 5 or 10 mg chrysotile B asbestos fibers in 0.5 ml saline, or 0.5 ml saline only (controls). Rats were killed at 1, 3, and 6 months postinstillation. Serotonin and histamine were quantitated in lung tissue homogenate using high-performance liquid chromatography with electrochemical and fluorometric detection, respectively. Serotonin was also quantitated in the cytoplasm of grouped (NEB) and individual (NEC) neuroendocrine cells and in mast cells using formaldehyde vapor-induced fluorescence and microspectrofluorometry, and density indices of NEBs, NECs, and mast cells were determined. Tissue edema, fibrotic lesions, and medial hypertrophy of pulmonary arterioles were assessed morphometrically. Test rats had higher pulmonary serotonin and histamine levels than controls at 1, 3, and 6 months. They also had higher cellular serotonin in NEBs at 1 month, but not in NECs, and tended to have higher serotonin levels in mast cells at 6 months. Mast cell numbers were higher among tests at 1 and 3 months, whereas NEBs and NECs were unchanged by asbestos. There was no difference between tests and controls in the amount of tissue edema at any time. However, all test rats had distinct lung lesions characterized by peribronchiolar fibrosis and bronchiolitis obliterans. No such lesions were present among control rats. Typically, mast cells were located immediately beneath the epithelial basal lamina of the bronchiolar fibrotic projections and at their stalks, whereas no mast cells were noted beneath normal epithelium, indicating a role of mast cells in asbestos-induced peribronchiolar fibrosis. Moreover, arteriolar medial hypertrophy at all three ages in conjunction with the increased levels of serotonin was an index of putative chronic pulmonary hypertension. Our results suggest that asbestos-induced rises in serotonin and histamine are due primarily to increased numbers of mast cells.

Synthesis and biological activity of analogs of dynorphin-A(1-13) substituted in positions 2 and 4: design of [Ala2,Trp4]-Dyn-A(1-13) as a putative selective opioid antagonist

Mono- and di-substituted analogs of dynorphin-A(1-13) (Dyn-A(1-13)) were synthesized by the solid-phase procedure. The products were purified and analyzed for their ability to inhibit the electrically evoked contractions of the guinea pig ileum (GPI) and mouse vas deferens (MVD) and to compete with the binding of [3H]etorphine ([3H]ET) and [3H]ethylketocyclazocine ([3H]EKC) to homogenates of rat brain (mu-, delta-, kappa 2-receptors) and guinea pig cerebellum (kappa-receptor), respectively. Introduction of Ala in position 2 caused a drastic decrease in the activity of the peptide on the smooth muscle preparations (IC50 of 104 and 2.250 nM in the GPI and the MVD as compared with 0.7 and 21 nM for the parent peptide, respectively). Conversely, this analog retained much of the opioid binding activity of Dyn-A(1-13) (relative binding potencies of 15 and 72% for the displacement of [3H]ET and [3H]EKC, respectively). The replacement of Phe4 by Trp also caused drastic decreases in the activity of the peptide in the smooth muscle preparations (relative potencies of 0.8 and 8.8% on the GPI and MVD) while much of the binding potency to the opioid receptors was retained (31 and 67% for the displacement of [3H]ET and [3H]EKC, respectively). [Ala2,Trp4]-Dyn-A(1-13) was the least potent peptide tested in the smooth muscle assays (relative potencies: 0.1 and 0.6%). However, this latter analog still retained some opioid binding activity in the displacement of [3H]ET to rat brain homogenates (3%).(ABSTRACT TRUNCATED AT 250 WORDS)

14-beta-Methyl-8-oxacyclorphan (BC-3016), a morphinan derivative with high affinity for kappa opioid receptor: comparison with dynorphin-A(1-13)

14-beta-Methyl-8-oxacyclorphan (BC-3016) was tested for its ability to depress the electrically evoked contractions of the guinea pig ileum (GPI) and of the mouse vas deferens (MVD) and to compete with the binding of prototype ligands selective for kappa-, mu-, or delta-opioid receptors in membrane preparations of rat brain and guinea pig cerebellum. BC-3016 was a very potent agonist in the GPI and MVD preparations, with ID50 of 0.7 and 31 nM, respectively. The activity of levorphanol, a standard alkaloid related to BC-3016, was much lower in both assays with ID50 values of 44 and 86 nM, respectively. Conversely, the activity of BC-3016 was quite comparable to that of dynorphin-A(1-13) in both preparations. In the GPI assay, a putative kappa-receptor antagonist, MR-2266, was 6.6 and 5.5 times more potent than naloxone in blocking the activity of BC-3016 and dynorphin-A(1-13), respectively. BC-3016 was also very potent in displacing bound [3H]ethylketocyclazocine ([3H]EKC) to membrane preparations of the guinea pig cerebellum, a brain component containing predominantly kappa-opioid receptors (Ki of 0.58 nM). Its potency in the displacement of the bound mu-ligand, 3H-labelled (D-Ala2,MePhe4,Gly-OH5)-enkephalin ([3H]DAGO), to rat brain homogenates was somewhat lower (Ki of 0.8 nM) but still high when compared with its ability to displace the delta-ligand, 3H-labelled (D-Ser2, Thr6)-Leu-enkephalin ([3H]DSLET) to rat brain homogenates (Ki of 4.45 nM). The affinity of BC-3016 for the opioid receptor was 2.1-fold higher than that of U-50488H, a selective kappa-opioid ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chrysotile asbestos on DNA synthesis and growth of human embryonic lung fibroblasts

The in vitro effects of asbestos fibers on thymidine (TdR3H) incorporation and growth of lung fibroblasts have been studied. Incubation of human embryonic lung fibroblasts with UICC Chrysotile B asbestos for 48 hr caused a 3 to 5-fold increase of TdR3H incorporation as compared with control cultures. This increase was dose-dependent with optimal effect obtained with doses as low as 10 micrograms/ml and with cell density of 5 X 10(4) fibroblasts per culture. However, enhanced TdR3H incorporation in treated cells was not correlated with an overall increase of the fibroblast population compared with control cultures as evidenced by cell counts and microscopic examination. Fibroblasts exposed to relatively low concentrations of UICC chrysotile (5-10 micrograms/ml) displayed an initial decrease in cell number compared to controls during the first 24 hr of incubation. At 48 hr however, enhanced TdR3H incorporation occurred with a concomittant increase in cell number. Moreover, continuous exposure of fibroblast cultures to chrysotile (10 micrograms/ml) for a longer period of time led to sustained increase of TdR3H incorporation and resumption of cell proliferation. It is suggested that increased thymidine incorporation is directly related to the effectiveness of asbestos in inhibiting the growth of lung fibroblasts and that measurement of TdR3H incorporation may represent a sensitive means of assessing rapidly the biological activity of asbestos. The possible relevance of this activity to asbestos-induced fibrogenesis and tumorigenesis is also discussed.

Comparative spinal analgesic action of dynorphin1-8, dynorphin1-13, and a kappa-receptor agonist U50,488

The effect of intrathecal injections of dynorphin1-8 (DYN1-8), dynorphin1-13 (DYN1-13), and a putative kappa agonist, U50,488 was tested in the rat tail-flick test. DYN1-8 and DYN1-13 (5, 10, 20 micrograms) produced a dose-related biphasic antinociceptive response consisting of an initial and a delayed response. Injection of U50,488 (20, 40 60 micrograms) produced a monophasic response. The antinociceptive effect of DYN1-8 (5, 10, 20 micrograms) and DYN1-13 (20 micrograms), was present 24 h postintrathecal injection. Pretreatment with systemic naloxone (2 mg/kg s.c.) attenuated the delayed response, but not the initial response induced by DYN1-8 and DYN1-13. The initial response was attenuated by pretreatment with intrathecal naloxone at a dose of 0.5 and 2.0 micrograms. The antinociceptive effect of U50,488 (20, 60 micrograms) was not affected by pretreatment with 2.0 micrograms intrathecal naloxone, but was significantly reduced by 4 micrograms of the antagonist. Both DYN1-8 and DYN1-13 (5 micrograms) augmented the antinociceptive effect of intrathecally administered morphine (5, 10 micrograms). Intrathecal injection of DYN1-8 (5, 10, 20 micrograms), DYN1-13 (5 micrograms), and morphine (10 micrograms) reduced the spontaneous output of urine measured at 2 and 24 h postintrathecal injection. A similar injection of U50,488 (20 micrograms) had no significant action on the urinary output. The results show that long and short dynorphin fragments have a comparable activity and the spinal antinociceptive actions of dynorphin are sensitive to low doses of intrathecal naloxone. The activity profile of spinally administered dynorphins differs from that of the kappa agonist U50,488.

Synthesis and biological activity of dynorphin-(1-13) and analogs substituted in positions 8 and 10

Dynorphin-(1-13) (Dyn-(1-13)) and various analogs substituted in positions 8 and 10 were synthesized by the solid-phase technique and analyzed for their ability to inhibit the electrically evoked contraction of the guinea pig ileum (GPI) and to compete with the binding of [3H]-ethylketocyclazocine (EKC, kappa ligand), [3H]-[D-Ala2, MePhe4-Gly-ol5]-enkephalin (DAGO, mu ligand) and [3H]-[D-Ser2, Thr6]-Leu-enkephalin (DSLET, delta ligand) to membrane preparations of the guinea pig cerebellum or rat brain. Introduction of Ala in position 8 decreased the activity of the peptide on the GPI by 50% but induced a 2.22-fold increase in its affinity for the kappa receptor ([3H]-EKC binding displacement from guinea pig cerebellum; Ki of 0.05 nM as compared with 0.11 nM for Dyn-(1-13)). On the other hand, the ability of [Ala8] Dyn-(1-13) to displace the binding of [3H]-DSLET from rat brain membranes was decreased by a factor of 1.7 while its affinity for the mu receptor was not greatly affected ([3H]-DAGO displacement; Ki of 0.44 nM as compared with 0.50 nM for Dyn-(1-13)). Replacement of position 8 by D-Ala caused similar changes in the activity of the peptide but the increase in its affinity for the kappa site was somewhat smaller (Ki of 0.08 nM as compared with 0.11 nM). [D-Pro10]-Dyn-(1-13) was equipotent to [Ala8]-Dyn-(1-13) in the GPI but its affinity for the mu binding site was decreased by a factor of 2.7 as compared with Dyn-(1-13).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoreactive dynorphine in maternal blood, umbilical vein and amniotic fluid

Immunoreactive dynorphin (ir-Dyn) was measured in maternal blood, umbilical vein and amniotic fluid after its extraction by passage through Sep Pak (C18 Waters). No significant change was observed in the plasma level of ir-Dyn in the first and second trimester of pregnancy as compared with plasma obtained from non-pregnant women. However, a 2.2 fold increase in ir-Dyn levels was observed during the third trimester as well as at delivery (1.07 and 1.09 pmoles per ml, respectively as compared with 0.48 pmoles per ml in control plasma). High levels of ir-Dyn were also found in the amniotic fluid (0.83 pmoles per ml) and the umbilical vein plasma (2.2 pmoles per ml). High pressure liquid chromatography analysis of maternal plasma ir-Dyn obtained at the end of the third trimester of pregnancy revealed the presence of multiple forms of ir-Dyn, the major peaks corresponding to the elution time of some previously identified placental ir-compounds namely Dyn-(1-11) and Dyn-(1-13). These data indicate that the levels of ir-Dyn in the maternal plasma at the third trimester of pregnancy and at delivery increase, a placental contribution to this phenomenon could be speculated.

Bombesin-like immunoreactivity in bovine adrenal medulla

The presence of immunoreactive (ir)-bombesin in bovine adrenal medulla, isolated adrenal chromaffin cells and subcellular fractions of the adrenal medulla was demonstrated using a specific antibody to the synthetic peptide. High levels of ir-bombesin were detected in acid (HCl) extracts of the adrenal tissue (27 pmol/g) and isolated cells (0.35 pmol per 10(6) cells). Subpopulations of adrenal chromaffin cells were also obtained by centrifugation of the original cell preparation through a stepwise bovine serum albumin gradient (cell layers I, II and III). The highest concentration of ir-bombesin (0.77 pmol/10(6) cells) was found in a cell population (cell layer I) enriched in noradrenaline (adrenaline/noradrenaline ratio of 0.6). At the subcellular level, ir-bombesin was mainly concentrated in the secretory granules (0.61 pmol/mg protein) along with catecholamines (1097 nmol/mg protein), but a relatively high concentration of ir-bombesin (0.26 pmol/mg protein) was also found in the microsomal fraction. Isolation and high performance liquid chromatography (HPLC) analysis of adrenomedullary ir-bombesin revealed the presence of four molecular forms, one of them corresponding to gastrin releasing peptide (GRP), another one (major peak) eluting closely to synthetic neuromedin B and another one coeluting with GRP-(18-27). HPLC analysis of the molecular forms of ir-bombesin in the microsomes and secretory granules indicated that GRP- and neuromedin B-like materials can be generated between the two fractions.

Interaction of dynorphin with kappa opioid receptors in bovine adrenal medulla

Dynorphin (Dyn) and various prototypic kappa opioid ligands were tested for their ability to bind to opioid receptors in a membrane preparation of bovine adrenal medulla and to modulate the release of catecholamines (CA) from isolated adrenal chromaffin cells. Saturation binding studies with [3H]-ethylketocyclazocine ([3H]-EKC) were performed at 37 degrees C for 30 min in the presence of [D-Ala2,Me-Phe4,Gly-ol5]-enkephalin (DAGO) and [D-Ser2,Thr6]-Leu-enkephalin (DSLET), two specific ligands for crossreacting mu and delta opioid receptors, respectively. Scatchard plot analysis of the data revealed the presence of two receptor sites: a high affinity binding site (kappa) with a KD of 0.66 nM and a Bmax of 12 pmoles/g protein and a low affinity binding site (kappa 2) with a KD of 11.1 nM and a Bmax of 56 pmoles/g protein. The presence of kappa opioid receptors in the membrane preparation was also supported by competition studies. U-50, 488H and Dyn-(1-13), two selective kappa opioid ligands, were potent inhibitors of [3H]-EKC binding with Ki (high affinity binding sites) of 2.5 and 2.3 nM, respectively. Among the various ligands tested for each class of opioid receptors (mu, delta, kappa), U-50, 488H and Dyn-(1-13) were the most potent inhibitors of the acetylcholine-evoked CA secretions from isolated adrenal chromaffin cells with IC50 of 0.31 and 1.14 microM, respectively. The inhibitory effect of U-50, 488H was significantly antagonized by diprenorphine and MR-2266, two opioid antagonists with a high affinity for the kappa opioid receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary bombesin in experimentally induced asbestosis in rats

The pulmonary levels of immunoreactive bombesin in normal rat lungs and rat lungs exposed to asbestos were determined. Experimental asbestosis was induced in rats by a single intratracheal injection of 5 mg or 10 mg UICC standard Canadian Chrysotile B while sham-operated control rats received only the saline carrier. At 1, 3, 6, and 9 months following instillation, 5 animals of each group were sacrificed and the lungs removed. A section was kept for morphologic analysis, while the remaining portion was submitted to acid extraction and later measured for bombesin content by radioimmunoassay (RIA). The Chrysotile B-exposed tissues displayed the characteristic features typical of the fibrotic state associated with asbestosis one month following exposure and thereafter. The pulmonary bombesinlike immunoreactivity ranged from 4.5-7.5 pmoles/g tissue in normal rat lung, and these levels remained unchanged at 1 and 3 months after asbestos exposure. However at 6 and 9 months, significant increases ranging between 2 and 2.5 fold were observed. The initial increases in bombesin levels occurred at a later time (6 months) than those already observed for vasoactive intestinal peptide (VIP) (3 months). However, VIP levels plateaued at 9 months, while those of bombesin were still increasing. High-pressure liquid chromatography (HPLC) coupled with RIA demonstrates the presence of two bombesin-immunoreactive peaks in normal rat lung, the major one coeluting with the mammalian bombesinlike peptide gastrin-releasing peptide (GRP) and the other one being presumably a C-terminal portion of GRP. These data indicate that immunoreactive bombesin and VIP are selectively increased at different times following asbestos instillation and that these changes occur after the onset of fibrosis and the appearance of well-defined fibrotic lesions.

Opioid receptors in bovine adrenal medulla

Using prototypic ligands for each type of opioid receptors (mu, delta, kappa, and sigma) as well as compounds derived from each class of endogenous opioid peptides (beta-endorphin, enkephalins, and dynorphins), we have undertaken the characterization of adrenomedullary opioid binding sites. The specific binding of [3H]etorphine ([3H]ET) to a membrane preparation of bovine adrenal medulla was greatly increased when the incubation temperature was raised from 22 to 37 degrees C. Characterization of the opioid binding sites was obtained at 37 degrees C with [3H]ET (nonspecific opioid ligand), [3H]ethylketocyclazocine ([3H]EKC; kappa), [3H]dihydromorphine ([3H]DHM; mu), [3H]-[D-Ala2,D-Leu5]enkephalin ([3H]DADLE: delta), and N-[3H]allylnormetazocine ([3H]SKF-10047; sigma) in the absence or presence of blocking agents for cross-reacting receptors. [3H]ET had a high affinity binding site (KD = 0.98 nM) with a Bmax of 119 pmol/g protein. All the other opioid compounds showed biphasic saturation curves with KD ranging from 0.6 to 1.29 nM for the high affinity binding site and from 2.49 to 12.1 nM for the low affinity binding site. The opioid mu-receptor was characterized by the high affinity binding site for [3H]DHM (KD = 1.29 nM; Bmax = 38 pmol/g protein). Blockade of the cross-reacting receptor sites for [3H]EKC, [3H]DADLE, and [3H]SKF-10047 revealed the presence of kappa (KD = 0.66 nM; Bmax = 12 pmol/g protein), kappa 2 (benzomorphan site; KD = 11.1 nM; Bmax = 56 pmol/g protein), delta (KD = 0.67 nM; Bmax = 4.7 pmol/g protein), and sigma (KD = 4.54 nM; Bmax = 32 pmol/g protein) opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and biological activity of monothionated analogs of leucine-enkephalin

The synthesis of the four regioisomers of monothionated Leu-enkephalins (Leu-Enk) from previously reported protected precursors is described. The Tyr1-thio analog was obtained as a 1:1 mixture of the L- and D-Tyr diastereomers. The pure compounds were tested for opiate-like activity by using the guinea-pig ileum (GPI) and mouse vas deferens (MVD) preparations, by assessing analgesic effects following intra-cerebroventricular administration and by examining their ability to displace [3H]-D-Ala2, D-Leu5-enkephalin (DADLE) and [3H]-dihydromorphine from rat brain homogenates. The results demonstrate that depending on the backbone position of the thioamide function, activity can be decreased or increased. In the smooth muscle preparations as well as in the opiate binding tests, the activity of D,L-Tyr1-thio-Leu-Enk and Gly3-thio-Leu-Enk was reduced. The activity of the latter analog was also diminished in the analgesia test. In all biological assays, Phe4-thio-Leu-Enk was either equally or slightly less potent than the parent compound. However, introduction of the sulfur atom in position 2 of Leu-Enk increased the potency of the compound in all assays, the MVD assay being the most sensitive. The results are interpreted in terms of the thioamide (amide) function in receptor recognition processes, the probable behavior of thiopeptides toward physiologically relevant peptidases and the structural divergences between tissue-specific receptors.

Effect of enkephalin on the micturition cycle of the cat

The effect of the synthetic opiate [D-Ala2, Me-Phe4]-leu-enkephalin ( DAMLE ) on the micturition cycle of the cat was studied. In vivo assays were performed with young male cats under two different conditions: 1) decerebrated cats (D-cats), with an intercollicular transection of the brainstem, and 2) spinal cats (S-cats), with a spinal transection between C5-C6. In vitro studies were carried out on bladder strips taken from adult male cats. The D-cats showed two types of voiding patterns: the first type (I) was characterized by a smooth wave of pressure and an incomplete emptying of the bladder; the second type (II) began like the type I, but ended with a series of small contractions accompanied by small jets of liquid, resulting in the complete emptying of the bladder. DAMLE inhibited vesical contractions and completely inhibited voiding in D-cats at doses equal or superior to 250 micrograms/kg i.v.; no effect was noted with lower doses. Vesical contractions were hardly affected in S-cats, even at high doses (greater than 350 micrograms/kg i.v.). DAMLE did not affect electrically induced contractions of isolated bladder strips. Naloxone not only antagonized the inhibitory effects of DAMLE , but also induced per se a contraction of the bladder. These results indicate that enkephalinergic neurons are involved in the central neural circuitry of the micturition cycle in the cat, with an inhibitory effect at the level of either the ascending spinal pathways or the pontine Barrington 's center.

Dynorphin-(1-13). I. Structure-function relationships of Ala-containing analogs

Dynorphin-(1-13) (Dyn-(1-13] and its analogs substituted by single introduction of Ala in positions 1-11 were synthesized by the solid-phase method and purified by high pressure liquid chromatography. Relative potencies of the synthetic compounds were determined by their ability to inhibit electrically-evoked contractions of the guinea pig ileum (GPI) and of the mouse vas deferens (MVD) and to compete with [3H]-etorphine for opiate receptors in rat brain homogenates. Introduction of Ala in positions 1 and 4 of Dyn-(1-13) provoked most important decreases in the activity of the molecule in the three assays (relative potency of 0.2% or less). Substitution of Ala in positions 2 or 5, but not 3, also severely decreased the potency of the peptide in the smooth muscle preparations (0.6-5.0% activity). However, the opiate receptor binding assay was less sensitive to the replacement of residue in position 2 (20% activity) than that in positions 3 or 5 (12% and 6% relative potencies, respectively). In the GPI assay and the opiate binding test, the other substitutions which greatly lowered the potency of the molecule were seen in positions 6, 7, 9 and 11, four basic residues. Among these, Arg6 and Arg7 were demonstrated to be the most important in the three biological tests. Finally, the replacement of Ile8 by Ala increased the relative potency of Dyn-(1-13) up to 191% and 900% in the MVD and the opiate binding tests, respectively.

Dynorphin and enkephalins in adrenal paraneurones. Opiates in the adrenal medulla

Immunoreactive dynorphin (ir-Dyn), immunoreactive leucine-enkephalin (ir-Leu-Enk) and various other neuropeptides were measured in acid extracts of bovine adrenal medulla and isolated adrenal chromaffin cells. Their respective levels ranged as follows: Leu-Enk greater than Dyn greater than bombesin greater than vasoactive intestinal peptide (VIP) greater than neurotensin greater than substance P. Comparisons of the total catecholamine levels with the levels of Leu-Enk in both extracts gave ratios in the same order of magnitude (2600, tissue extract and 5000, cell extract). However, the catecholamine/Dyn ratio in the tissue extract (138 000) was much higher than that found in the cell extract (20 180), suggesting a possible selective degradation of Dyn in tissue extract as compared with cell extract or an induction of Dyn biosynthesis in cells which have been isolated from their natural microenvironment. Immunofluorescence staining of isolated chromaffin cell sections revealed the presence of ir-Dyn in 5 to 10% of the total cell population. To localize ir-Dyn in regard to Leu-Enk and catecholamines, adrenal chromaffin cells were separated into three populations (I, II, and III) on a stepwise bovine serum albumin (BSA) gradient. Relative high levels of ir-Dyn were measured in cell layer I (4 pmol/10(6) cells), a cell population enriched in noradrenaline. However, ir-Leu-Enk was more concentrated in cell layers II and III (5.3 and 8.3 pmol/10(6) cells), two populations enriched in adrenaline. Isolation and high pressure liquid chromatography (HPLC) analysis of adrenomedullary Dyn indicated the presence of at least five molecular forms corresponding to Dyn-(1-11), Dyn-(1-12), Dyn-(1-13), Ala-containing-Dyn-(1-13) and a nonidentified molecule eluting closely to Dyn-(1-13). These data indicate that adrenal ir-Dyn and ir-Leu-Enk have distinct cellular distributions. In addition, the identification of Dyn fragments in bovine adrenal medulla indicates that these short peptides may be considered as natural active forms of Dyn.

Asbestos-related increase in pulmonary levels of vasoactive intestinal peptide (VIP)

Vasoactive intestinal peptide (VIP), leucine-enkephalin (Leu-Enk), dynorphin (Dyn), neurotensin (NT) and substance P (SP) were measured by radioimmunoassay in lung and bronchoalveolar lavage (BAL) fluids of sham operated control rats and rats exposed to asbestos (5 and 10 mg, single intratracheal injections) for 3 and 6 months. Among these peptides, VIP, Leu-Enk and Dyn were the most abundant with 6 to 25 pmoles per g of lung tissue as compared with 0.95 to 1.2 pmoles per g for the other neuropeptides. In the presence of asbestos, VIP levels were selectively increased up to 2.7 times in lung tissue and 4.3 times in BAL fluids. On high pressure liquid chromatography (HPLC), the immunoreactive VIP coeluted with synthetic VIP. It is concluded that this selective increase may be involved in the pathogenesis of asbestos-related diseases. Exposure to asbestos causes chronic inflammatory reactions in the lung which may lead to fibrosis (1) and increase the incidence of pleuropulmonary cancers (2). Little is known concerning the biochemical changes responsible for the deleterious effects of asbestos on pulmonary functions. Previous studies have documented the vast complexity and diversity of lung biochemistry including its ability to metabolize lipids, inactivate certain enzymes and produce physiologically active amines (3-6). Recently, the lung has been recognized as an important source of peptidergic substances. VIP and SP were reported to be localized in nerve terminals of the main airways and in axons of the parasympathetic conducts (7-11). Other neuropeptides including bombesin (12, 13), calcitonin (13, 14) and Leu-Enk (13) were also detected in the lung. However, these latter peptides were mainly confined to diffuse granule-containing cells also known as APUD cells (amine precursor uptake and decarboxylation cells) (15). The role of these neuropeptides in normal lung function and in pulmonary diseases is unknown. However, it has recently been demonstrated that APUD cells proliferate in the rat lung following asbestos inhalation (16) and lung exposure to carcinogens (17, 18). In addition, Moody et al. (19) and Sorenson et al. (20) have observed high levels of bombesin in human cell lines derived from small-cell lung carcinoma. It was then of particular interest to verify if lung exposure to asbestos can induce some changes in the levels of various neuropeptides. In the present study, we report that VIP is significantly increased in the lungs and BAL fluids of rats exposed to asbestos while no significant change in the levels of Leu-Enk, Dyn, NT and SP is observed.

Distinct distribution of immunoreactive dynorphin and leucine enkephalin in various populations of isolated adrenal cromaffin cells

The distribution of immunoreactive-dynorphin (ir-Dyn) in isolated subpopulations of bovine adrenal chromaffin cells was examined and compared with that of adrenaline (A), noradrenaline (NA) and ir-Leucine-Enkephalin (ir-Leu-Enk). Using a stepwise bovine serum albumin (BSA) gradient, various populations of catecholamine-storing cells were separated and designated as cell layers I, II and III. Cell layer I contained more NA than A; cell layer II contained slightly more A than NA whereas cell layer III was highly enriched in A. The original cell preparation contained 2.9 times more ir-Leu-Enk than ir-Dyn (4.7 and 1.6 pmoles per 10(6) cells, respectively). After separation of the cells on BSA gradient, ir-Dyn was mainly detected in cell layer I (4.0 pmoles/10(6) cells) whereas ir-Leu-Enk was concentrated in cell layer III (8.3 pmoles/10(6) cells). Both peptides were secreted in response to acetylcholine (5 x 10(-5) M), but the amount secreted was in accordance with the cell content in each peptide. After subcellular fractionation of the adrenal medulla, the neuropeptides were found in close association with catecholamines in the secretory granules. These results indicate that bovine adrenal chromaffin cells can be isolated according to their specific content in A, NA and opioid peptides and are consistent with the hypothesis of distinct biosynthetic pathways for Dyn and the Enk.

Purification and identification of multiple forms of dynorphin in human placenta

Immunoreactive dynorphin (ir-Dyn) and opiate-like peptides (OLP) were measured in acid (HC1) extracts of human placenta by the use of an antibody to synthetic Dyn-(1-13) and of the displacement of [3H]-naloxone binding to rat brain homogenates, respectively. The placenta contained 57.6 pmoles per g of ir-Dyn and 134.4 pmoles per g of naloxone binding equivalents. After passage of the extract through cartridges of Sep Pak C18, half of the OLP was eluted with ir-Dyn at 35% acetonitrile (ACN), the rest being eluted at 60% ACN. Both fractions obtained from Sep Pak were chromatographed separately on Sephadex G-50, the OLP of the 35% ACN fraction coeluting with the ir-Dyn speak and that of the 60% ACN fraction being eluted at the same volume as synthetic beta-endorphin. Conversely, the fraction of OLP coeluting with synthetic leucine-enkephalin (Leu-Enk) in these two chromatographies was minimal. The Dyn-immunoreactive material was further purified by high pressure liquid chromatography on reverse phase micro-Bondapak C18 columns to give three distinct peaks corresponding to synthetic Dyn-(1-11), Dyn-(1-13) and Dyn-(1-12), respectively. Our results indicate that the human placenta contains several forms of ir-Dyn which account for about half of its endogenous OLP.

Evidence that inhibition of nicotine-mediated catecholamine secretion from adrenal chromaffin cells by enkephalin, beta-endorphin, dynorphin (1-13), and opiates is not mediated via specific opiate receptors

The opioid peptides Met- and Leu-enkephalin, dynorphin (1-13), and beta-endorphin and the narcotic analgesics, morphine, levorphanol, and dextrorphan all produced a dose-dependent inhibition of nicotine (5 x 10(-6) M)-mediated release of [3H]norepinephrine ([3H]NE) from bovine adrenal chromaffin cells in culture. None of these agents affected [3H]NE release induced by high K+ (56 mM). Although the above results suggest that the opioid peptides and narcotic analgesics inhibit catecholamine release from adrenal chromaffin cells in culture, we suggest that these effects are not mediated by specific opiate binding sites, since (1) the inhibition was only produced with high concentrations of the agents--the threshold concentrations were 10(-7) to 10(-5)M and higher; (2) the inhibition produced by the narcotic analgesics did not display stereospecificity, because the d-isomer, dextrorphan, was slightly more active than the l-isomer, levorphanol; (3) the narcotic antagonists naloxone, naltrexone, and levallorphan did not reverse the inhibition produced by either the narcotic analgesics (e.g., morphine) or the opioid peptides (e.g., dynorphin). These three antagonists themselves inhibited the nicotine-mediated release of [3H]NE from the adrenal chromaffin cells in culture. Finally (4), the I2-Tyr1 substituted analogues of beta-endorphin and dynorphin that are biologically less active than the parent compounds produced an inhibition of the nicotine-mediated [3H]NE release similar to that of their parent compounds. These results do not support the idea that high-affinity stereospecific opiate binding sites are involved in the inhibitory modulation of nicotinic evoked catecholamine release from bovine adrenal chromaffin cells in culture.

Dynorphin in bovine adrenal medulla. I. Detection in glandular and cellular extracts and secretion from isolated chromaffin cells

The presence and secretion of immunoreactive dynorphin in bovine adrenal medulla and isolated adrenal chromaffin cells were examined and compared with those of immunoreactive leucine-enkephalin. Using an antiserum raised against dynorphin-(1-13), a sensitive and highly specific radioimmunoassay was developed. A nearly intact antigen was required for recognition by the antiserum since it did not react with leucine-enkephalin and reacted poorly with dynorphin-(1-12) (cross-reactivity 0.5%) and other fragments of dynorphin-(1-13). On the other hand, the antibody used for detection of leucine-enkephalin did not cross-react with dynorphin(1-13). Adrenal medulla acid extracts contained 195 times more immunoreactive leucine-enkephalin than dynorphin. However, the concentration of immunoreactive dynorphin in acid extract of freshly isolated adrenal chromaffin cells was only 1.4 times smaller than that of leucine-enkephalin. Incubation of the isolated chromaffin cells in the presence of acetylcholine, nicotine, high potassium, but not muscarine, induced a concomitant release of immunoreactive dynorphin (3.5-9% of total cell content) and leucine-enkephalin (6.5-11.4% of total cell content).

Dynorphin in bovine adrenal medulla. II. Isolation, partial characterization and biological activity of two distinct molecules

Two highly potent dynorphin-like peptides were isolated from bovine adrenal medulla by successive chromatography of an acid (HCl) extract on Sephadex G-10, carboxymethylcellulose, Sephadex G-50 and partition chromatography on Sephadex G-50. Amino acid analysis of both peptides revealed the presence of 24 amino acids including the composition of dynorphin-(1-13) and differing from each other only by a few residues. Both peptides were shown to have the same activity as dynorphin-(1-13) in the guniea pig ileum assay and reacted as well as dynorphin-(1-13) with a specific antibody (R-31) directed against the synthetic material.

Distinct regulations by calcium of cyclic GMP levels and catecholamine secretion in isolated bovine adrenal chromaffin cells

The effects of various calcium-dependent secretagogues on cyclic GMP levels and catecholamine (CA) secretion were measured in a preparation of bovine adrenal chromaffin cells. The secretory effect of acetylcholine (ACh; 8--10 fold stimulation) was mimicked by nicotine but not muscarine. Three--five fold stimulations of cyclic GMP levels were also obtained with ACh and muscarine but not nicotine. High concentration of K+, and the ionophore A23187, also elevated cyclic GMP levels. However, secretion produced by veratridine, ouabain, and the ionophore X537A was not accompanied by any rise in cyclic GMP levels. Removal of extracellular calcium significantly decreased both basal levels of CA secretion and of cyclic GMP and completely abolished their stimulation by ACh. The half-maximal effects of calcium on the cholinergic stimulations of cyclic GMP levels and of CA secretion were observed at 0.2 and 2.5 mM, respectively. Substitution of Ca2+ by Sr2+ was more effective in maintaining the cyclic GMP response than the secretory response. The calcium channel blockers Co2+, Mg2+ and Ni2+ inhibited the cholinergic stimulation of cyclic GMP more than that of CA release. On the other hand, the organic calcium channel blockers, verapamil and methoxyverapamil (D--600) were more effective antagonists of the secretory response. These data indicate that the cholinergic stimulations of CA secretion and of cyclic GMP levels in bovine adrenal chromaffin cells are regulated by calcium via two distinct mechanisms.

Studies on the inhibitory action of opiate compounds in isolated bovine adrenal chromaffin cells: noninvolvement of stereospecific opiate binding sites

In isolated bovine adrenal chromaffin cells, beta-endorphin, dynorphin, and levorphanol caused a dose-dependent inhibition of catecholamine (CA) secretion elicited by acetylcholine (ACh), with an ID50 of 50, 1.3, and 4.3 microM, respectively. The inhibition by the opiate compounds was specific for the release evoked by ACh and nicotinic drugs and was noncompetitive with ACh. Stereospecific binding sites for the opiate agonist [3H]etorphine were found in homogenates of bovine adrenal medulla (KD = 0.59 nM). beta-Endorphin, dynorphin, levorphanol, and naloxone were potent inhibitors of the binding of [3H]etorphine with an ID50 of 12, 0.4, 5.2, and 6.2 nM, respectively. However, [3,5-I2Tyr1]-beta-endorphin, [3,5-I2Tyr1]-dynorphin, and dextrorphan, three opiate compounds with no or little activity in the guinea pig ileum assay, were relatively ineffective in inhibiting the binding of [3H]etorphine (ID50 700, 600, and 10,000 nM, respectively). On the other hand, these three compounds were equipotent with beta-endorphin, dynorphin, and levorphanol, respectively, in inhibiting the ACh-evoked release of CA from the adrenal chromaffin cells (ID50 of 10, 1.5, and 6 microM, respectively). Inhibition of CA release was also obtained with naloxone (ID50 = 14) microM) and naltrexone (ID50 greater than 10(-4) M), two classical antagonists of opiate receptors, and this effect was additive to that of beta-endorphin. These data indicate that the opiate modulation of CA release from adrenal chromaffin cells is not related to the stimulation of the high affinity stereospecific opiate binding sites of the adrenal medulla. The physiological function of these sites remains to be determined.

Synthesis of peptides by the solid-phase method. IV. Des-Arg(9)-bradykinin and analogs

We have synthesized a series of 19 analogs of the octapeptide fragment of bradykinin (BK), des-Arg 9-bradykinin, in order to perform a structure-activity study of this peptide on the newly discovered B1 receptor of bradykinin. The first time, each residue of the octapeptide was replaced by L-alanine to pinpoint biologically important residues. Thereafter, both phenylalanine residues in positions 5 and 8 were substituted by L-tyrosine methyl ether, L-cyclohexylalanine, D-phenylalanine, and L-leucine. This paper describes the synthesis of the analogs by the solid phase method. A Beckman peptide synthesizer was used to assemble the peptides on the resin support. Couplings were performed by the symmetrical anhydribe procedure. After cleavage with liquid HF, the peptides were purified by ion-exchange chromatography on carboxymethyl-cellulose and by gel filtration on Bio-Gel P2 resin. The purity of the octapeptides was then checked by tic, paper electrophoresis, amino acid analysis, and elemental analysis. The new peptides were tested on the rabbit aorta in order to evaluate their kinin-like activities and to see if they act as antagonist. The results of the biological assays are discussed in terms of structure-activity relationships.

Studies on the inhibitory action of somatostatin in the electrically stimulated rat vas deferens

Somatostatin (SS) inhibits in a dose-dependent manner electrically evoked contractions in the rat vas deferens. This action was not modified by yohimbine, naloxone or a mixture of antagonists containing atropine, phentolamine, methysergide, burimamide, propranolol and indomethacin, but was markedly potentiated by reducing the Ca2+ concentration of the medium from 2.5 to 1.25 mM and greatly inhibited when increasing the Ca2+ concentration of the medium from 2.5 to 5.0 mM. Clonidine (CLO), but not beta-endorphin (ENDO) was affected similarly to SS by changing the Ca2+ concentration of the medium. The contractile effect of norepinephrine in unstimulated rat vas deferens was not altered by SS. These results were taken as an indication that SS produces its inhibitory action in the rat vas deferens by interacting with specific SS and its receptors presumably located in the cell membranes of adrenergic nerve terminals. The interaction between SS and its receptors may provoke a decreased diffusion of Ca2+ ions into the nerve terminals and/or a decreased mobilisation of Ca2+ ions from intraneuronal stores thus leading to a reduction in electrically evoked release of norepinephrine.

Systemic administration of beta-endorphin: potent hypotensive effect involving a serotonergic pathway

In normal adult rats anesthetized with urethane, intravenous injections of beta-endorphin (30--150 micrograms kg-1) induced a transient fall of blood pressure followed by a small hypertension and a prolonged hypotension. Prior administration of naloxone completely blocked these effects, whereas naloxone, given 1 hr after beta-endorphin, did not reverse the prolonged depressor phase of the opioid peptide. The effects of beta-endorphin on the arterial blood pressure were greatly reduced in animals pretreated with p-chlorophenylalanine, a specific depletor of serotonin. Moreover, in rats pretreated with potent serotonin antagonists such as cyproheptadine, mianserin, and metergoline, beta-endorphin did not produce a significant hypotension. Furthermore, the depressor effect of beta-endorphin was potentiated by fluoxetine, a specific serotonin uptake inhibitor. These observations suggest the participation of a serotonergic pathway in the action of beta-endorphin on the arterial blood pressure.

Rat vas deferens: a specific bioassay for endogenous opioid peptides

The electrically-evoked contractions of the rat vas deferens were selectively inhibited by beta-endorphin, the preparation being much less sensitive to enkephalins and narcotic analgesic drugs. However, introduction of D-Ala in position 2 of [Leu]-enkephalin enhanced the activity of the opioid peptide to the order of that of beta-endorphin. It is concluded that the rat vas deferens preparation constitutes a specific bioassay for endogenous opioid peptides and related compounds.

Synthesis and biological activity of ovine beta-lipotropin-(41--91)-henkaipentekontapeptide

The 51-residue peptide ovine beta-lipotropin-(41--91) has been synthesized by the solid-phase method in about 5% overall yield. The synthetic product was characterized by partition chromatography on agarose gel, thin-layer chromatography in two solvent systems, paper electrophoresis at two pH values, polyacrylamide gel electrophoresis, amino acid analyses of acid and enzymic hydrolysates, and bioassay for lipolytic and melanotropic activities. The synthetic peptide is about 5.4 times as active on a weight basis as ovine beta-lipotropin in the lipolytic assay. In the melanotropic assay, it was about 2.4 times more active than the beta-lipotropin but only 5% as active as bovine beta-melanotropin. It had negligible opiate activity in the guinea pig ileum assay.

Synthesis and biological activity of beta-melanotropins and analogues

Synthetic [Arg8]-, [Gly10]-, and [Phe12]-beta cl-MSH and beta p-MSH have been prepared by the solid-phase method. Their lipolytic and melanotropic activities have been compared to each other and with those of previously synthesized beta cl-MSH, [formyl-Trp12]-beta cl-MSH, and beta b-MSH. Replacement of Bln8 of beta cl-MSH by Arg causes a greater decrease in melanotropic activity than lipolytic activity. However, when Phe10 of beta cl-MSH is replaced by Gly, both activities are destroyed. Alteration or replacement of Trp12 of beta cl-MSH by formyl-Trp or Phe has little effect on the melanotropic activity while the lipolytic activity is greatly decreased. Replacement of Ser2 of beta b-MSH by Glu induces a three fold increase in melantropic activity but it does not affect the lipolytic activity.

Synthesis and biological activity of camel and bovine beta-melanotropins

Two natural occurring melanotropins, camel betaC2-MSH and bovine beta-MSH, have been synthesized by improved solid-phase procedures. The coupling reaction of tert-butyloxycarbonylamino acids was achieved by using their preformed symmetrical anhydrides. The synthetic hormones were purified by gel filtration on Sephadex G-10 and G-25, chromatography on carboxymehtylcellulose, and partition chromatography on Sephadex G-25 with final yields of 56 and 35% for betac2-MSH and betab-MSH, respectively. They were then shown to be identical with their natural hormones in amino acid analysis, paper electrophoresis, disc electrophoresis, thin-layer chromatography, enzymic digests, and bioassays. Bioassay data of these two synthetic melanotropins indicate that the replacement of Ser by Gly in betab-MSH does not change its melanocyte-stimulating activity.

Adenosine-3',5'-monophosphate-dependent protein kinase from bovine anterior pituitary gland. 3. Structural specificity of the ATP site of the catalytic subunit

The effect of analogues and derivatives of adenosine 3′,5′-monophosphate (cyclic AMP) and of ATP on the incorporation of 32P from [γ-32P]ATP into histones has been measured using the purified catalytic subunit of adenohypophyseal protein kinase. Gamma-labeled CTP, GTP, and UTP cannot substitute for [γ-32P]ATP but they slightly inhibit the phosphorylation by [γ-32P]-ATP when present as unlabeled compounds. A stringent requirement of the adenine nucleus is observed for the ability to compete at the ATP site, inhibitions of 42, 39, 32, and 63% being observed respectively with adenine, adenosine, 5′AMP, and ADP, while the corresponding purine or pyrimidine derivatives have no effect when present at a 13-fold molar excess relative to [γ-32P]ATP. The N6-benzoyl and N6-butyryl derivatives of cyclic AMP are inactive whereas the 8-substituted derivatives are generally as active as cyclic AMP itself, except for the 8-amino- and 8-hydroxy-derivatives, which exhibit a lower degree of competition. All cyclic AMP and ATP analogues and derivatives that inhibit histone phosphorylation by [γ-32P]ATP act as competitive inhibitors. Such competition at the ATP site of the catalytic subunit of protein kinase probably accounts for the progressive inhibition of cyclic-AMP-dependent protein kinase activity measured at high concentrations (above 10−5 M) of the cyclic nucleotide.