Alpha-thioglycerol sensitive excitatory oxytocin receptors in fowl rectum

The selective antagonism of the excitatory responses of oxytocin by alpha-thioglycerol and its potentiation by Mg++ indicate the presence of specific oxytocin receptors in fowl rectum. In addition, the sensitivity of the rectum to very small doses of oxytocin suggests a possible facilitatory role of neurohypophyseal hormones in oviposition.     

Lipid peroxidation,low-level chemiluminescence and regulation of secretion in the mammary gland

In mammary explants of lactating mice, changes in the intensity of chemiluminescence (CL) were observed after the addition to the incubation medium of hormones and mediators that are involved in the regulation of secretion: oxytocin, acetylcholine, epinephrine and norepinephrine. A 15-min period of treatment with oxytocin, epinephrine or norepinephrine changed the level of thiobarbituric acid-reactive substances (TBARS). Two mammary explants, one of which was treated with oxytocin, acetylcholine, epinephrine or norepinephrine, were found to interact even when separated by a quartz glass wall. Analysis of the level of TBARS formation in these two explants showed that the observed interactions might be connected with light emission resulting from lipid peroxidation (LP) processes. The possible role of LP and low-level CL in the regulation of mammary gland secretion is discussed.     

2-o-Iodotyrosine]-oxytocin and [2-o-methyltyrosine]-oxytocin: basic pharmacology and comments on their potential use in binding studies

Both [2-o-iodotyrosine]-oxytocin and [2-o-methyltyrosine]-oxytocin display only weak vasopressor and antidiuretic effects on rats. They inhibit the in vitro uterotonic action of oxytocin; this inhibition is not fully competitive. It is concluded that they are not suitable as markers for studies of uterine receptor for oxytocin.     

Paraventricular neurones in the rat hypothalamic slice: Lucifer Yellow injection and immunocytochemical identification

Summary Intracellular records were obtained from paraventricular neurones injected with Lucifer Yellow in slices from the rat hypothalamus. Slices containing fluorescent neurones were then serially cut and alternating sections were stained immunocytochemically for vasopressin or oxytocin. Double-labelled cells were found which fluoresced and which had reacted with either vasopressin, or oxytocin antiserum.This study was supported in part by grant 3.469.79 from the Swiss National Science Foundation.     

[2-o-Iodotyrosine]-oxytocin and [2-o-methyltyrosine]-oxytocin: Basic pharmacology and comments on their potential use in binding studies

Summary Both [2-o-iodotyrosine]-oxytocin and [2-o-methyltyrosine]-oxytocin display only weak vasopressor and antidiuretic effects on rats. They inhibit the in vitro uterotonic action of oxytocin; this inhibition is not fully competitive. It is concluded that they are not suitable as markers for studies of uterine receptor for oxytocin.Supported by the Swiss National Science Foundation, grant No. 3.2080.73.Deceased 30 April 1975.     

Modification of the contractile responses of rabbit mammary strips to oxytocin by prostaglandin E1.

PGE1 administration to isolated strips from pregnant and lactating rabbit mammary gland resulted in different effects on oxytocin-induced contractions. In strips from pregnant animals, oxytocin action was enhanced; in those from lactating animals, it was reduced and threshold doses for oxytocin were markedly higher.     

α-Thioglycerol sensitive excitatory oxytocin receptors in fowl rectum

Summary The selective antagonism of the excitatory responses of oxytocin by -thioglycerol and its potentiation by Mg⁺⁺ indicate the presence of specific oxytocin receptors in fowl rectum. In addition, the sensitivity of the rectum to very small doses of oxytocin suggests a possible facilitatory role of neurohypophyseal hormones in oviposition.Acknowledgment. The authors wish to express their sincere thanks to Dr M.S. Sastry, Head of the Division and Dr C.M. Singh, Director of the Institute for providing the facilities and Mr Dev Singh for his technical assistance.     

Oxytocin analogs effective as noncompetitive inhibitors in uterotonic test

Summary Deamino-1-carba-oxytocin analogs with a chemically reactive group in position 4 were demonstrated to act as noncompetitive oxytocin inhibitors in the assay on isolated rat uterus.     

Der Oxytocingehalt im menschlichen pathologischen Liquor

Summary The quantity of oxytocin in the cerebrospinal fluid is decreased by brain atrophy and infantile brain damage, not injured by multiple sclerosis but increased by meningitis, sciatica and drug controlled convulsions. Immediately after a seizure, the oxytocin level is very strong raised.

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Diese Arbeit wurde mit Mitteln des Ministeriums für Wissenschaft und Technik der DDR durchgeführt.     

Pharmacological versus binding analysis of receptor systems: How do they interplay? Myometrial cell receptors for oxytocin as a paradigm

Summary Binding studies in various biological systems frequently indicate the presence of several binding sites for a biologically active ligand. They differ in their affinity for the ligand in question, binding capacity, and Hill coefficient, which suggests differences in the mechanisms of the binding site-ligand interactions. Identification of the true receptors (sites initiating a cellular response) appears to be difficult. Three clusters of binding sites for oxytocin were found on rat myometrial cells. The oxytocin receptor seems to be linked to the medium-affinity site; the cooperation between the high-and medium-affinity sites in eliciting the uterotonic response seems likely, but lacks experimental proof. Dose-response analysis in partially irreversibly inhibited uterus preparations, the method of equipotent doses (Furchgott-Bursztyn method), and structure-activity analysis of oxytocin-like peptides acting as competitive inhibitors of oxytocin, turned out to be suitable for pharmacological analysis of this receptor system.     

Die Wirkung von synthetischem Oxytocin (Syntocinon) und Acetazolamid auf die Ausscheidung von Wasser,Natrium und Kalium

Summary Changes in water, sodium, and potassium excretion following administration of synthetic oxytocin (Syntocinon)—alone or in combination with acetazolamide— resemble the changes that occur after an equivalent dose of neurohypophysial extract containing oxytocin. Since the action of Syntocinon on water and sodium excretion is manifest when carbonic anhydrase in kidney tissue is fully inhibited by acetazolamide, it may be assumed that the mechanism whereby Syntocinon increases sodium excretion is independent of carbonic anhydrase. Oxytocin does not affect ultrafiltration in the glomeruli (Krause ⁴) and would therefore appear to modify the reabsorption or excretion process in the tubuli.     

Die Wirkung von Vasopressin und Oxytocin auf das Nervensystem von Insekten

Summary Vasopressin and oxytocin are antagonistically effective substances with inverse dependence on concentration in the nervous system of insects. These results emphasize the central importance of neurohormonal control of general response in the nervous system.     

Pharmacological versus binding analysis of receptor systems: how do they interplay? Myometrial cell receptors for oxytocin as a paradigm.

Binding studies in various biological systems frequently indicate the presence of several binding sites for a biologically active ligand. They differ in their affinity for the ligand in question, binding capacity, and Hill coefficient, which suggests differences in the mechanisms of the binding site-ligand interactions. Identification of the 'true' receptors (sites initiating a cellular response) appears to be difficult. Three clusters of binding sites for oxytocin were found on rat myometrial cells. The oxytocin receptor seems to be linked to the medium-affinity site; the cooperation between the high- and medium-affinity sites in eliciting the uterotonic response seems likely, but lacks experimental proof. Dose-response analysis in partially irreversibly inhibited uterus preparations, the method of equipotent doses (Furchgott-Bursztyn method), and structure-activity analysis of oxytocin-like peptides acting as competitive inhibitors of oxytocin, turned out to be suitable for pharmacological analysis of this receptor system.     

Effects of three synthetic peptides analogous to neurophypophyseal hormones on the excitability of giant neurones of Achatina fulica Férussac.

Deamino-dicarba-(D-D)oxytocin and D-D-Arg-vasotocin at 10(-4)Kg/l showed an excitatory effect on the periodically oxcillating neurone (PON) of Achatina fulica Férussac. D-D-Arg-vasopressin had no effect.     

Use of three specific radioimmunoassays in measuring neurohypophysial hormone content and plasma concentrations of vasopressin, oxytocin and DDAVP in rats after prolonged infusion of DDAVP

Specific radioimmunoassays (RIA) were employed for measuring plasma and neurohypophysial concentrations of oxytocin (OT) and vasopressin (AVP) after administration of 1-deamino-8-D-Arg-vasopressin (DDAVP). DDAVP concentrations were measured by a newly-developed specific RIA. Through the use of minipumps, DDAVP was infused i.p. over a period of 3 days in normally hydrated rats. Despite decreased urine production and increased urine osmolality no changes could be observed in neurohypophysial and plasma hormone concentrations.     

Affinity of 1,2-substituted oxytocin analogues to the uterus receptor: Free-Wilson and Hansch analysis.

The analysis of pA2 values for 1,2-substituted oxytocin analogues suggests a significant resonance effect of p-substituted groups in 2-tyrosine when the hormone binds to its uterus receptor, whereas the N-terminal amino group exerts less clearly characterized effects (participation of its lipophilicity and molecular volume can be assumed.     

Über Peptidsynthesen,XLIII. Darstellung einiger Oxytocin-Analoga

Summary Four new analogues of oxytocin, i.e. Phe²-Ser⁴-Ileu⁸-oxytocin, Phe³-Ser⁴-Ileu⁸-oxytocin, Gly⁴-Ileu⁸-oxytocin and Phe²-Val³-oxytocin have been synthesized and their biological activities compared with those of oxytocin (Syntocinon®).

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XLII. Mitt.:E. Schröder, Justus Liebigs Annln Chem., im Druck.     

Use of three specific radioimmunoassays in measuring neurohypophysial hormone content and plasma concentrations of vasopressin,oxytocin and DDAVP in rats after prolonged infusion of DDAVP

Summary Specific radioimmunoassays (RIA) were employed for measuring plasma and neurohypophysial concentrations of oxytocin (OT) and vasopressin (AVP) after administration of 1-deamino-8-D-Arg-vasopressin (DDAVP). DDAVP concentrations were measured by a newly-developed specific RIA. Through the use of minipumps, DDAVP was infused i.p. over a period of 3 days in normally hydrated rats. Despite decreased urine production and increased urine osmolality no changes could be observed in neurohypophysial and plasma hormone concentrations.     

Antidiuretic effects of oxytocin in the Brattleboro rat

The antidiuretic activity of oxytocin (OT) was measured in Brattleboro rats with congenital diabetes insipidus. A dose dependent antidiuretic response was found in animals receiving chronic infusions of 0.1 micrograms/h, 1.0 micrograms/h, and 5 micrograms/h of OT. OT infused at the rate of 5 micrograms/h over a 7-day period completely reversed the symptoms of diabetes insipidus. The results support the concept that OT serves as a weak agonist of vasopressin at the level of the kidney and at pharmacological levels exhibits antidiuretic activity.     

Affinity of 1,2-substituted oxytocin analogues to the uterus receptor: Free-Wilson and Hansch analysis

Summary The analysis of pA₂ values for 1,2-substituted oxytocin analogues suggests a significant resonance effect of psubstituted groups in 2-tyrosine when the hormone binds to its uterus receptor, whereas the N-terminal amino group exerts less clearly characterized effects (participation of its lipophilicity and molecular volume can be assumed).Supported by the Swiss National Science Foundation, grant No. 3.040.76.