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D Gazis

Publications and source records attributed to D Gazis.

At least 37 records · Page 2Linked to original sources
PubMed1985

Synthesis and biological activities of a fluorescent photoaffinity analog of vasopressin.

The present study describes the synthesis and biological activities of a vasopressin (VP) analog which binds covalently to receptors via a photoreactive p-azido group in position 3 and which contains a rhodamine label in position 8 for localization of hormone-receptor complexes by image-intensified fluorescence microscopy. 1-Deamino[3-(p-azidophenylalanine)]-N epsilon-rhodamyllysine-VP (Rhod-N3-dLVP) was obtained in a two-step procedure from the precursor 1-deamino[3(p-aminophenylalanine)]-LVP which was synthesized by a solid phase technique. The rat antidiuretic activity of this compound was 0.34 +/- 0.3 U/mg. Although both Rhod-N3-dLVP and its congener without a rhodamine label, N3-dLVP, did not have any hydroosmotic activity in the isolated toad urinary bladder in the absence of UV light, after UV irradiation they increased both urea and water transport across the bladder wall. Moreover, these permeability effects of Rhod-N3-dLVP persisted during prolonged and repeated periods of washout, suggesting that the photoproducts of this analog had formed covalent complexes with toad bladder receptors. Binding of Rhod-N3-dLVP was inhibited when photolysis was carried out in the presence of 1-deamino-LVP. These studies suggest that Rhod-N3-dLVP has the requisite biological properties to serve as a tool for the localization by fluorescence microscopy of VP receptors in various target tissues.

Affinity Labels↗
PubMed1984

Influence of sarcosine or N-methylalanine in position 7 on the antagonistic properties of [1-deaminopenicillamine]- and [1-(beta-mercapto-beta, beta-cyclopentylmethylene-propionic acid)]-vasopressin.

Substituting sarcosine or N-methylalanine for proline in the inhibitory vasopressin analogs dPAVP and d(CH2)5AVP had the following effects: 1) milk ejection and antidiuretic activities were severely depressed, 2) pressor antagonism was maintained but weakened somewhat, and 3) antagonism in the uterus in vitro was maintained, but no consistent pattern was seen.

Alanine↗
PubMed1984

Antidiuretic and pressor activities of vasopressin analogs with L-alaninamide and D-alaninamide substitutions at position 9.

Analogs of arginine vasopressin (AVP) and lysine vasopressin (LVP)--with an L-alaninamide residue or a D-alaninamide residue replacing the naturally occurring glycinamide in position 9--lose virtually all pressor activity but retain from 10 to 70% of the antidiuretic activity of their parent hormones. These findings, in conjunction with the data of others on the biological consequences of alterations in positions 7 and 8, show that the antidiuretic receptor will tolerate considerably more structural alteration in the C-terminal tripeptide "tail" of the vasopressins than will the pressor receptor.

Animals↗
PubMed1983

Synthesis and some pharmacological properties of oxytocin and vasopressin analogues with sarcosine or N-methyl-L-alanine in position 7.

Eight analogues of oxytocin and arginine-vasopressin were synthesized, in which the proline residue in position 7 was replaced by either sarcosine or N-methylalanine; some of the pharmacological properties of these analogues were evaluated. In peptides containing a beta-mercaptopropionic acid residue in position 1, the additivity of the effects of deletion of the amino group in position 1 and of the above-noted replacements in position 7 on biological properties of these analogues was ascertained. All of the analogues were found to be potent in either antidiuretic or uterine activity and also selective in action. From the point of view of pharmacological properties, substitution of sarcosine in position 7 of oxytocin gave analogues with higher oxytocic and milk-ejecting activities than did the substitution of N-methylalanine. The opposite structure-activity relationship was observed with arginine-vasopressin, where the N-methylalanine-containing analogues were more potent than the sarcosine-containing analogues with respect to pressor activity and also, if not deaminated, with respect to antidiuretic activity.

Alanine↗
PubMed1983

Synthesis and some pharmacological properties of [4-threonine,7-sarcosine]oxytocin, a peptide with high oxytocic potency, and of [4-threonine,7-N-methylalanine]oxytocin.

Two analogues of oxytocin, [Thr4,Sar7]- and [Thr4,MeAla7]oxytocin, were synthesized and their pharmacological properties investigated. [Thr4,Sar7]oxytocin was found to exhibit high biological activity (uterotonic activity of 1174 +/- 104 and milk ejection activity of 731 +/- 57 units/mg) and high selectivity for oxytocin-like relative to vasopressin-like activities (antidiuretic activity of 0.037 +/- 0.012 unit/mg, undetectable pressor activity). [Thr4,MeAla7]oxytocin was characterized by markedly lower biological activities. In both analogues, the additivity of the effects of the residues in positions 4 and 7 of oxytocin on the biological activity of the analogues was ascertained.

Animals↗
PubMed1983

Biofunctional evaluation of two hydrogen bonds stabilizing the beta-turn in the acyclic component of oxytocin.

The depsipeptide [8-alpha-hydroxyisocaproic acid, 9-glycolic amide]-oxytocin, which has ester linkages replacing the peptide linkages between the 7th and 8th and the 8th and 9th residues of oxytocin, has been synthesized by a (6 + 3) condensation of Boc-tocinoic acid with Pro-O-HyIc-O-Glyc-NH2, followed by deprotection of the resulting product. The analog exhibited the following activities in rats: 258 +/- 11 and 28 +/- 5 U/mg, uterus in vitro in the absence and presence, respectively, of Mg+2; 54 +/- 4 U/mg, uterus in vivo; 19.3 +/- 2.1 U/mg, milk ejection; 0.153 +/- 0.026 U/mg, antidiuretic activity; and no pressor activity. The need for the presence of the peptide linkages mentioned above as sources for internal hydrogen bonds to stabilize the "biologically significant" conformation is discussed.

Amino Acid Sequence↗
PubMed1983

[1-Desaminopenicillamine, 8-alpha-hydroxyisocaproic acid] oxytocin. A selective inhibitor in rats of the uterine response to oxytocin.

[1-Desaminopenicillamine, 8-alpha-hydroxyisocaproic acid] oxytocin was synthesized by a 6 + 3 fragment condensation from precursors which had been formed by solution methods. This analog inhibited uterine responses to oxytocin (pA2 7.37, 7.9, 6.17; uterus in vitro without Mg++, in vitro with Mg++, and in vivo, respectively) and showed little or no activity in other bioassays.

Amino Acid Sequence↗
PubMed1983

Role of the carboxamide groups of the asparagine and glycinamide residues of oxytocin. Syntheses and biological properties of [5-beta-cyanoalanine] oxytocin and [9-alpha-aminoacetonitrile] oxytocin.

In an attempt to see whether the C=O and the NH2 of CONH2 of asparagine5 and glycinamide9 are both essential for biological activity, [5-beta-cyanoalanine] oxytocin and [9-alpha-aminoacetonitrile] oxytocin have been synthesized. Each of these analogs contains a nitrile group in place of the carboxamide group of Asn5 and GlyNH92 respectively; the nitrile group can simulate the carbonyl portion of the carboxamide, but lacks the hydrogen-bond donating capacity of its NH2 portion. Substitution of a nitrile group produced opposite biological effects in the 5 and the 9 positions; the 5-substituted analog showed very low activities (less than 3% of those of oxytocin) while the 9-substituted analog showed extremely high activities (with an in vivo uterine activity of 906 U/mg almost twice that of oxytocin). The results clearly suggest that the mechanisms of interaction of the carboxamide groups with the receptor sites are different for residues 5 and 9.

Animals↗
PubMed1982

Solid-phase synthesis of peptides via alpha, beta-unsaturated amino acids: oxytocin, simultaneous incorporation of amide functions in COOH-terminal and endo-positions.

Oxytocin was synthesized via the solid-phase method using dehydroalanine as pseudo-protecting group of the carboxyl-terminal as well as the omega-amide functions of asparagine and glutamine in endo-position. Starting with Boc-Gly-Dha-resin and using Boc-L-Asp(Dha-NHEt)-OH and Boc-L-Glu(Dha-NHEt)-OH as precursors of asparagine and glutamine, respectively, oxytocin was assembled in stepwise manner under solid phase synthesis conditions. Treatment of the protected [Glu(Dha-NHEt)4, Asp(Dha-NHEt)5]-oxytocin-Dha-resin with 1 n HCl in glacial acetic acid in the presence of 3 equiv. water removed the peptide from the support with the simultaneous formation of the asparagine and glutamine residues to give the protected nonapeptide amide: Cbz-Cys(Bzl)-Tyr(Bzl)-Ile-Gln-Asn-Cys(Bzl)-Pro-Leu-Gly-NH2, which was deprotected with sodium in liquid ammonia and then oxidized with diiodoethane to give oxytocin. After purification by gel chromatography and countercurrent distribution, the product displayed the chemical and physical properties and oxytocic activity (533 +/- 301U/mg) of a standard oxytocin preparation.

Amino Acids↗
PubMed1982

Biofunctional evaluation of a hydrogen bond stabilizing the conformation in the cyclic part of oxytocin.

[5-beta-Malamidic acid]oxytocin was synthesized to study the importance of the hydrogen bond between the C=O of Tyr2 and the peptide N-H of Asn5 for the stabilization of a biologically functional conformation of oxytocin. This analog lacks the peptide N-H at residue 5 required for the formation of a hydrogen bond with the C-O of Tyr2. [5-beta-Malamidic acid] oxytocin exhibited 45.1 +/- 2.5 U/mg and 65.6 +/- 5.9 U/mg of uterotonic activity, in vitro, in the absence and in the presence, respectively, of Mg2+, 147 +/- 14 U/mg of uterotonic activity in vivo, 203 +/- 13 U/mg of milk-ejecting activity, 0.37 +/- 0.03 U/mg of pressor activity and 0.32 +/- 0.29 U/mg of antidiuretic activity. It is concluded that devoid of the hydrogen bond under question, an oxytocin-like peptide can still assume the conformation needed to interact with the oxytocin receptors.

Drug Stability↗
PubMed1980

Biofunctional evaluation of a hydrogen bond stabilizing the beta-turn in the acyclic part of oxytocin.

In a continued effort to determine the importance of the hydrogen bonds for stabilization of the biologically active conformation of oxytocin, deamino-[9-glycolicamide] oxytocin was synthesized in order to study, in this respect, the hydrogen bond between the peptide N--H of Gly9 and the C=0 of Cys6. In this analog the amide linkage between residues at positions 8 and 9 is replaced by an ester. Thus the residue at position 9 cannot be involved in hydrogen bond formation with the C=O of Cys6. Deamino-[9-glycolicamide] oxytocin exhibited 134 +/- 13 U/mg and 355 +/- 48 U/mg of uterotonic activity in absence and in presence, respectively, of Mg2+, 108 +/- 8 U/mg of milk-ejecting activity, 0.35 +/- 0.03 U/mg of pressor activity and 2.5 +/- 0.1 U/mg of antidiuretic activity. It is concluded that the hydrogen bond under question is not critical for the conformation required for biofunctional interaction of oxytocin with its receptors in the uterus, mammary gland and other target organs.

Amino Acid Sequence↗
PubMed1980

The design of effective in vivo antagonists of rat uterus and milk ejection responses to oxytocin.

Several new synthetic analogs of the oxytocin antagonist [1-deaminopenicillamine]oxytocin have been prepared and tested for their abilities to inhibit responses to oxytocin by the isolated rat uterus in the absence and presence of Mg++, by the rat uterus in situ, and by the rat mammary gland in situ. Substituting 2-O-methyltyrosine in [1-deaminopenicillamine]oxytocin strikingly enhances antagonism of all uterin responses, and [1-deaminopenicillamine, 2-O-methyltyrosine]oxytocin and its 4-threonine analog are also potent inhibitors of the milk ejection response. Substituting 2-phenylalanine in [1-deaminopenicillamine]oxytocin also enhances antagonistic activities in all uterine assays, but [1-deaminopenicillamine, 2-phenylalanine]oxytocin retains agonistic activity on milk ejection assays. From these studies we can conclude that changes in the 1-position (1-deaminopenicillamine substitution) and the 2-position (2-O-methyltyrosine or 2-phenylalanine substitution) can have additive effects on antagonistic activities. Substitution of an 8-ornithine also enhances inhibitory potency in vivo, and this effect may also be additive to those of the substitutions in 1- and 2-positions. These findings provide many clues that may lead to the design of even more effective antagonists; several of the analogs reported here appear to the most effective antagonists of oxytocin in vivo yet reported and may be useful agents in further studies on the physiological functions of endogenous oxytocin.

Animals↗
PubMed1980

Synthesis of [8-alpha-hydroxyisocaproic acid]oxytocin. Biological activities and comparison of its in vivo uterine actions to those of deamino-[8-alpha-hydroxyisocaproic acid]oxytocin, deamino-oxytocin and oxytocin.

The synthesis and biological activities of [8-alpha-hydroxyisocaproic acid]oxytocin are reported. The in vivo uterine responses to [8-alpha-hydroxyisocaproic acid] oxytocin are prolonged and those to deamino-[8-alpha hydroxyisocaproic acid] oxytocin (as well as those we have previously reported for deamino-oxytocin) are very prolonged as compared with those of oxytocin. Time courses of the in vivo uterine responses to deamino-[8-alpha-hydroxyisocaproic acid]oxytocin and deamino-oxytocin (as followed by plotting the intervals between the individual contractions of a response vs. time after peptide injection) differ from those to [8-alpha-hydroxyisocaproic acid]oxytocin and oxytocin.

Animals↗
PubMed1978

Elimination of infused arginine-vasopressin and its long-acting deaminated analogue in rats.

Arginine-vasopressin (AVP) and deamino-arginine-vasopressin (dAVP) were infused into rats. When the concentrations of the two peptides were steady, the rate of clearance of AVP from the plasma was six times the rate of clearance of alphaAVF. Only 6% of the infused AVP was excreted unchanged in the urine, whereas approximately 100% of the dAVP was excreted. When the infusions were stopped, AVP disappeared from the plasma much more rapidly than dAVP. The plasma concentrations of the two peptides did not decay as simple exponential functions, suggesting that both AVP and dAVP entered a slowly exchanging compartment or compartments during prolonged infusion. These differences in the metabolic clearance of AVP and dAVP may well explain the prolonged antidiuretic effect of dAVP in rats.

Animals↗