Biomedical subjects

B Castro

Publications and source records attributed to B Castro.

At least 73 records · Page 4Linked to original sources

PubMed1986

Analysis of inactive renin by renin profragment monoclonal antibodies.

Two peptides were synthesized, corresponding to the sequences (-19 to -7) and (-26 to -17) of the prorenin prosegment. Monoclonal antibodies were raised to these sequences and used to characterize human plasma inactive renin. Only anti (-19 to -7) reacted with inactive renin, as measured by direct assay or affinity chromatography. The data were used to evaluate two possible inactive renin stuctures: plasma inactive renin is a truncated prorenin lacking the prosegment N-terminal portion; its spatial conformation masks the N-terminal extremity, preventing interaction of this region with specific antibodies.

Antibodies, Monoclonal↗

PubMed1986

Solid-phase peptide synthesis of human(Nle-27)-oxyntomodulin. Preliminary evaluation of its biological activities.

Oxyntomodulin is a peptide isolated from porcine intestine which consists of the whole glucagon sequence extended at its C-terminal part by a basic octapeptide. The analogue (Nle-27)-oxyntomodulin of the human sequence has been synthesized by solid-phase peptide synthesis, purified by HPLC and identified. Its biological activities are the same as those of the natural hormone.

Amino Acid Sequence↗

PubMed1986

Evidence for dopaminomimetic effect of intrastriatally injected cholecystokinin octapeptide in mice.

The behavioural effect of intrastriatally injected cholecystokinin sulphated octapeptide (CCK-8S), and its interactions with the antagonists Z-CCK-(27-32)NH2 and proglumide, were investigated in mice. When injected into the right striatum, CCK-8S (0.05-1 ng) induced contralateral rotations, as did the dopamine agonist apomorphine. Non-sulphated CCK-8 was inactive and sulphated desamino-CCK-7 was only weakly active in this respect. CCK-8S-induced turning was antagonized by co-injected Z-CCK-(27-32)NH2 (0.01-10 ng) or proglumide (0.1-1 micrograms), as well as by intraperitoneal injection of the neuroleptic drug haloperidol. These data suggest that CCK-8S may, in these conditions, stimulate dopamine-mediated neurotransmission, and that Z-CCK-(27-32)NH2, in addition to its peripheral effect, is also a very potent CCK antagonist at the striatal level.

Animals↗

PubMed1986

Pharmacological profile of a new peptidic gastrin antagonist.

Boc-Trp-Met-Asp-NH2 was described as the smallest peptidic fragment which presented gastric antisecretory activity. Some pharmacological aspects of a peptide analogue, Boc-Trp-Leu-Asp-NH2 (Boc-WLD-NH2), were studied on the main biological functions of gastrin. This compound was found to inhibit the binding of gastrin to isolated gastric fundic mucosal cells (IC50 50 microM). On pentagastrin-induced gastric acid secretion in the rat, a dose-dependent inhibition was observed with an ID50 of 55 mumol/kg when pentagastrin (1 microgram/kg per h) was continuously infused and with an ID50 of 7.8 mumol/kg when pentagastrin (1 microgram/kg) was bolus i.v. injected. Similar inhibition was observed on acid secretion induced by pentagastrin in the isolated rat gastric mucosa (IC50 100 microM), whereas the tripeptide had no effect when acid output was triggered by histamine. A dose-dependent inhibition with the tripeptide was shown on pentagastrin induced guinea-pig ileum contractions (IC50 31 microM). The compound had no activity on histamine-stimulated guinea-pig atria (histamine H2-receptor). These results suggest some evidence for a selective antigastrin activity.

Animals↗

PubMed1986

Synthesis of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin and evaluation of their biological activity on acid secretion.

The syntheses of pseudo-tetrapeptides Boc-Trp-psi (CH2-NH)-Met-Asp-Phe-NH2 21 and Boc-Trp-Met-psi (CH2-NH)-Asp-Phe-NH2 20, representing the C-terminal tetrapeptide sequence of gastrin, in which amide bonds were replaced by CH2-NH bond, are described, as well as the syntheses of pseudo-peptide analogues Boc-Trp-psi (CH2-NH)-Nle-Asp-Phe-NH2 16, Boc-Trp-Nle-psi (CH2-NH)-Asp-Phe-NH2 11, and Boc-Trp-Nle-Asp-psi (CH2-NH)-Phe-NH2 5, in which the methionyl residue was replaced by a norleucyl residue. Pseudo-peptides 16 and 21, in which the amide bond between Trp and Met (or Nle) was substituted by a CH2-NH bond, stimulated gastric acid secretion in the rat in vivo. Pseudo-peptides 11 and 20, where the amide bond between Met (or Nle) and Asp was replaced by a CH2-NH bond, did not exhibit any activity on acid secretion in the rat in vivo but were potent inhibitors of pentagastrin-induced acid secretion. Peptides 11, 16, 20 and 21 all recognize the gastrin receptor on a mucosal cell preparation. Pseudo-peptide 5, in which the amide bond between Asp and Phe was replaced by a CH2-NH bond, was a less potent inhibitor of pentagastin-induced acid secretion and had a weaker affinity than the other pseudo-peptides.

Amino Acid Sequence↗

PubMed1986

Solution synthesis of antigenic and inhibiting peptides of the human renin prosegment-1. [Tyr47, Nle53] preprorenin-(47-60) peptide methyl ester.

The [Tyr47, Nle53] preprorenin (47-60) peptide methyl ester, a tetradecapeptide related to the human renin prosegment, has been synthesized using a three-segment coupling strategy. Selective deprotection of the segments before coupling allowed an easy removal of the final tetradecapeptide side chain-protecting groups by acidolysis and an easy purification. Antibodies raised against this peptide bound the plasmatic inactive renin.

Amino Acid Sequence↗

PubMed1986

Solution synthesis of antigenic and inhibiting peptides of the human renin prosegment-2. [Tyr40] preprorenin-(40-50) peptide methyl ester.

The [Tyr40] preprorenin (40-50) peptide methyl ester, an undecapeptide related to the human renin prosegment, has been synthesized using a stepwise strategy with hydrogenolisable protections on the side chains. The final deprotection was very difficult as observed by 1H NMR and reversed phase HPLC. 2D 1H NMR spectroscopy of the purified peptide allowed the assignment of all protons.

Amino Acid Sequence↗

PubMed1986

[Conditions for the use of specific antibodies for immunohistochemical visualization of serotonin and melatonin in the pineal gland of sheep].

Having prepared antisera to serotonin and to melatonin, the authors were able to show that, in the pineal gland, the behaviour of these two antisera in immunohistochemical studies differs. The antiserum raised against 5HT, actually bound to the molecule formed by condensation of formaldehyde on 5HT and therefore could be used to reveal 5HT in tissue fixed with formaldehyde. On the other hand, the anti-melatonin antiserum bound to melatonin, and could therefore be used to reveal its presence in fresh tissue.

Animals↗

PubMed1985

Inhibition of human renin by synthetic peptides derived from its prosegment.

The primary structure of human preprorenin has recently been determined from its cDNA sequence. It includes a 46-amino acid NH2-terminal prosegment. Six peptides corresponding to the entire prosegment (9-40), except for the NH2-terminal (1-8) and COOH-terminal (41-46) ends have been synthesized. These peptides were tested for their inhibitory effect on human plasma renin activity. Boc-Tyr-Thr-Thr-Phe-Lys-Arg-Ile-Phe-Leu-Lys-Arg-Met-Pro-OMe (where Boc represents t-butoxycarbonyl and OMe represents methoxy) (h Y(9-20) and its fragment Boc-Leu-Lys-Arg-Met-Pro-OMe h (16-20) were the most potent inhibitors with IC50 values of 2 X 10(-4) and 3 X 10(-4)M, respectively. Peptides located near the COOH-terminus were less inhibitory. The inhibitory capacity of h (16-20) was studied further on highly purified human renin acting on either pure human angiotensinogen or a synthetic human tetradecapeptide substrate. In both of these assays its inhibitory potency was about 10-fold greater than that found on plasma renin activity. Peptide h (16-20) was 3-6 times less potent in inhibiting human renin than its mouse counterpart m (15-19) was in inhibiting mouse renin. Kinetic studies carried out with h (16-20) showed a mixed type of inhibition. When human angiotensinogen was used as substrate, Ki and K'i values were 17.7 +/- 3.9 and 2.9 +/- 0.9 microM, respectively. These studies showed that human renin, like mouse renin and pepsin, can be inhibited by peptides derived from its prosegment. In addition, as in the case of pepsin, they suggest that the NH2-terminal part of the prosegment interacts more strongly with the active enzyme.

Amino Acid Sequence↗

PubMed1985

Abilities of some tryptophan and phenylalanine derivatives to inhibit gastric acid secretion.

Benzotript (N-p-chlorobenzoyl-L-tryptophan) has been shown to be a receptor-antagonist in vivo and in vitro for peptides from the gastrin family. In the present study, we examine tryptophan, and some of its N- and C-acylated derivatives, as well as some phenylalanine derivatives, to show their ability to inhibit gastrin-induced acid secretion in the rat in vivo and to compete for the binding of [125I]-(Leu-15)-HG-17 to its cellular receptor on rabbit isolated gastric mucosal cells. N- and C- derivatives of tryptophan and phenylalanine were found to inhibit gastrin-induced acid secretion and binding of [125I]-(Leu-15)-HG-17 to its mucosal cell receptors. By either criterion, the relative antagonistic potencies of the compounds tested were: tert-butyloxycarbonyl-L-tryphophan-p-nitrophenyl ester approximately equal to tert-butyloxycarbonyl-L-tryptophan-carbamoylmethyl ester greater than tert-butyloxycarbonyl-L-tryptophyl-L-methionyl-carbamoylmethyl ester approximately equal to tert-butyloxycarbonyl-L-phenylalanine-carbamoylmethyl ester approximately equal to tert-butyloxycarbonyl-L-tryptophyl-L-methionyl-amide greater than tert-butyloxycarbonyl-L-tryptophan greater than tert-butyloxycarbonyl-L-phenylalanine greater than benzyloxycarbonyl-L-tryptophan approximately equal to benzotript, with minor differences between the in vivo and the in vitro experiments. These results demonstrate that both the nature of the amino acid residue and the N- and C-substitutions are important in determining antagonist activity and affinity for gastrin receptors.

Animals↗

PubMed1985

Synthesis of the C-terminal octapeptide of pig oxyntomodulin. Lys-Arg-Asn-Lys-Asn-Asn-Ile-Ala: a potent inhibitor of pentagastrin-induced acid secretion.

The synthesis of Lys-Arg-Asn-Lys-Asn-Asn-Ile-Ala representing the C-terminal octapeptide of oxyntomodulin isolated from pig intestine is described. Its structure was confirmed by its 360-MHz 1H NMR spectra. The octapeptide was tested for its ability to inhibit pentagastrin-induced acid secretion, in the anaesthetized rat, in the conscious rat with chronic gastric fistula, and in the conscious cat with gastric chronic fistula. The octapeptide inhibits pentagastrin-induced acid secretion in all three models. Compared to oxyntomodulin, the parent hormone, the synthetic peptide was approximately 150 times less potent but has the same efficacy. Biological data are presented and discussed.

Animals↗

PubMed1985

Synthesis and biological activities of some pseudo-peptide analogues of tetragastrin: the importance of the peptide backbone.

Pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin, in which a peptide bond has been replaced by a CH2-NH bond, i.e. (tert-butyloxycarbonyl)-L-tryptophyl-psi (CH2-NH)-L-leucyl-L-aspartyl-L-phenylalanine amide (8), (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-psi (CH2-NH)-L-aspartyl-L-phenylalanine amide (13), (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-L-aspartyl-psi (CH2NH)-L-phenylalanine amide (20), were synthesized. The pseudo-peptides 8 and 13 were shown to have the same affinity as (tert-butyloxycarbonyl)-L-tryptophyl-L-leucyl-L-aspartyl-L-phenylalanine amide (21) for the gastrin receptor on isolated mucosal cells. The pseudo-peptide 20 exhibited lower affinity (IC50 congruent to 10(-5) M). The biological activity of these pseudo-peptides was studied on acid secretion in the anesthetized rat. Compound 8 stimulated acid secretion, identically with that of 21. Compound 13 did not exhibit any agonist activity but was able to antagonize the action of gastrin (ED50 = 0.3 mg/kg). Compound 20 did not show any agonist activity but was able to inhibit gastrin-induced acid secretion, with lower potency (ED50 = 15 mg/kg). The importance of the peptide bonds in the mode of action of gastrin is discussed, and a hypothetical approach of the mechanism of action is presented.

Animals↗

PubMed1985

Structure-activity relationships of C-terminal tri- and tetrapeptide fragments that inhibit gastrin activity.

A series of tri- and tetrapeptide derivatives, analogues of the gastrin C-terminal region with no phenylalanine residue, were synthesized. These peptides were tested for their ability to inhibit gastrin-stimulated acid secretion in vivo as well as binding of [125I]-(Nle11)-HG-13 to gastric mucosal cell receptors in vitro. Most of the peptides tested exhibited gastrin antagonist activity in vivo and in vitro. Most active derivatives were 20-30 times more potent than the well-known gastrin antagonist derivatives proglumide and benzotript and had 20-200 times more binding affinity. The smallest fragment exhibiting antagonist activity was the tripeptide Boc-L-tryptophyl-L-methionyl-L-aspartic acid amide.

Animals↗

PubMed1985

Synthesis of aldehydic peptides inhibiting renin.

Reduction of peptidyl N, O-dimethyl hydroxamates with lithium aluminium hydride in diethyl ether at 0 degree allowed the preparation of peptidyl aldehydes in excellent yield and optical purity. These aldehydic peptides are able to inhibit renin activity. They are the shortest renin inhibitors known to date.

Aldehydes↗

PubMed1985

Immunologic identification of both plasma and human renal inactive renin as prorenin.

Antibodies were raised against a synthetic tetradecapeptide which is a component of the non-renin portion (prosegment) of human renin precursor. Inactive renin from human kidney and plasma strongly adsorbed to a gel coupled to immunoglobulins purified from such an antiserum. These results suggest that renal and circulating inactive human renins contain in their structure the prosegment of prorenin.

Antibody Specificity↗

PubMed1984

Aldehydic peptides inhibiting renin.

Aldehydic peptides in which the C terminal residue is leucinal or phenylalaninal were synthesized. These compounds exhibited potent inhibition of renin activity and appeared to be precursors of transition state analogues for renin-catalysed amide bond hydrolysis.

Aldehydes↗

PubMed1984

Synthesis and biological activity of new peptide segments of gastrin exhibiting gastrin antagonist property.

A series of C-terminal peptide segments of gastrin, i.e., (tert-butyloxycarbonyl)-L-tryptophyl-L-methionyl-L-aspartic acid amide, (tert-butyloxycarbonyl)-glycyl-L-tryptophyl-L-methionyl-L-aspartic acid amide, (tert-butyloxy-carbonyl)-L-tyrosyl-glycyl-L-tryptophyl-L-methionyl-L-asp artic acid amide, and (benzyloxycarbonyl)-L-glutamyl-L-alanyl-L-tyrosyl-glycyl-L-tryptophyl-L -methionyl-L-aspartic acid amide were prepared and were shown to competitively inhibit the binding of labeled human gastrin to its receptors in an isolated gastric mucosal cell preparation and to antagonize the action of gastrin on gastric acid secretion (ED50 from 1.5 to 7 mg/kg) in vivo in the reperfused rat stomach, determined according to the method of Ghosh and Schild. From these studies, it could be concluded that the C-terminal phenylalanine residue, which is of primary importance for intrinsic biological gastrin-like activity, is not essential for binding to gastrin receptors.

Amino Acid Sequence↗

PubMed1984

Synthesis of peptides related to the prosegment of mouse submaxillary gland renin precursor: an approach to renin inhibitors.

The complete sequence of the structural gene coding for mouse submaxillary gland renin was recently reported and the amino acid sequence of preprorenin was deduced. This sequence includes a 45-amino acid peptide that corresponds to the prosegment of the renin precursor. To investigate whether peptides related to the renin prosegment are able to inhibit renin activity, we have synthesized four peptides having the following structures: Arg-Ile-Pro-OMe, butyloxycarbonyl(Boc)-Leu-Lys-Lys-Met-Pro-OMe, Boc-Arg-Ile-Pro-Leu-Lys-Lys-Met-Pro-OMe, and Boc-Glu-Arg-Ile-Pro-Leu-Lys-Lys-Met-Pro-OMe (corresponding to amino acids 12-14, 15-19, 12-19, and 11-19, respectively, of the renin prosegment). All four peptides were found to inhibit the activity of pure mouse submaxillary renin on a porcine synthetic tetra-decapeptide in vitro, and the most potent inhibitors exhibited IC50 values in the micromolar range. Enzymatic kinetic studies carried out using peptide 15-19 showed an uncompetitive or a mixed type of inhibition with a Ki value of 2.3 X 10(-6) M at 37 degrees C in 0.5 M citrate/phosphate buffer (pH 6.0).

Amino Acid Sequence↗