Synthesis and some pharmacological properties of [1-beta-mercapto-beta,beta-diethylpropionic acid,2-(3,5-dibromo-L-tyrosine)]oxytocin.

The synthesis of the protected polypeptide precursor of [1-beta-mercapto-beta,beta-diethylpropionic acid,2-(3,5-dibromo-L-tyrosine)]oxytocin was performed in a stepwise manner by solution techniques. This analog of oxytocin has two modifications, each of which taken alone gives analogs which inhibit some of the pharmacological responses to oxytocin. The S-ethylcarbamoyl protecting groups of beta-Mpa(beta-Et2)(Ec)-Dbt-Ile-Gln-Asn-Cys(Ec)-Pro-Leu-Gly-NH2 were removed in refluxing liquid NH3, and the resulting disulfhydryl compound was oxidatively cyclized in H2O-MeOH with ICH2CH2I. Purification was effected by partition chromatography and gel filtration. The analog possesses antioxytocic (pA2 = 7.08) and antiavian vasodepressor (pA2 = 7.38) activities but has neither agonist nor antagonist activity in the rat pressor assay. These potencies are close to those exhibited by [1-beta-mercaptopropionic acid,2-(3,5-dibromo-L-tyrosine)]oxytocin but different from those of [1-beta-mercapto-beta,beta-diethylpropionic acid]oxytocin.     

Synthetic metabolites of neurohypophyseal hormones. (Des-9-glycinamide)oxytocin and (des-9-glycinamide, des-8-leucine)oxytocin.

Syntheses and biological properties are reported for two analogs of oxytocin in which the glycinamide and the leucylglycinamide moiety, respectively, have been deleted from the parent hormone. Both [des-9-glycinamide]oxytocin and [des-9-glycinamide,des-8-leucine]oxytocin are weak agonists in the rat uterotonic and antidiuretic assays but possess no detectable rat pressor activity. In addition, [des-9-glycinamide]oxytocin is an inhibitor of the oxytocin-induced vasodepressor response in fowl but is a potent agonist in the hydroosmotic assay of the toad urinary bladder.     

Synthesis and some pharmacological properties of (3-beta-(2-thienyl)-L-alanine)-8-lysine-vasopressin.

[3-beta-(2-Thienyl)-L-alanine]-8-lysine-vasopressin was synthesized by solution techniques. The partially protected heptapeptide Boc-Cys(Ec)-Tyr-Thi-Gln-Asn-Cys(Ec)-Pro (1) was synthesized in a stepwise manner using the active ester method or the dicyclohexylcarbodiimide (DCC) coupling technique mediated by 1-hydroxybenzotriazole (HBt). The protected nonapeptide amide Boc-Cys(Ec)-Tyr-Thi-Gin-Asn-Cys(Ec)-Pro-Lys(Coc)-Gly-NH2 (2) was prepared by coupling 1 with Lys(Coc)-Gly-NH2 using DCC-HBt. From 2, [3-thienylalanine]-8-lysine-vasopressin was obtained by removing the Boc-protecting groups with trifluoroacetic acid and ethylcarbamoyl (Ec) protecting groups in refluxing liquid NH3 followed by oxidative cyclization in H2O-MeOH using ICH2CH2I. Purification was effected by partition chromatography followed by gel filtration. The highly purified product possesses activities in the oxytocic, avian vasodepressor, rat pressor, and antidiuretic assays of 19.0 +/- 0.5, 87 +/- 4, 243 +/- 5, and 332 +/- 32 units/mg, respectively. Thus [3-thienylalanine]-8-lysine-vasopressin has higher oxytocic, avian vasodepressor, and antidiuretic potencies than does 8-lysine-vasopressin, whereas its pressor potency is about the same as or slightly lower than that of 8-lysine-vasopressin.     

(1-Beta-mercaptopropionic acid, 2-(3,5-dibromo-L-tyrosine))oxytocin, a potent inhibitor of oxytocin.

[1-Beta-Mercaptopropionic acid,2-(3,5-dibromo-L-tyrosine)]oxytocin was synthesized from a protected polypeptide intermediate that had been prepared by the condensation of S-ethylcarbamoyl-beta-mercaptopropionyl-3,5-dibromotyrosine with H-Ile-Gln-Asn-Cys(Ec)-Pro-Leu-Gly-NH2, using dicyclohexylcarbodiimide in dimethylformamide. The ethylcarbamoyl (Ec) protecting groups were removed by refluxing NH3, and the resulting disulfhydryl peptide was oxidatively cyclized to the corresponding disulfide by ICH2CH2I. Purification of the analog was effected by partition chromatography and gel filtration. The analog possesses antioxytocic (pA2 = 7.05) and antiavian vasodepressor (pA2 = 7.44) activities but has neither agonist nor antagonist activity in the rat pressor assay.     

Effects of oxytocin and (1-penicillamine,4-threonine) oxytocin on thermoregulation in rats

Direct administration of either oxytocin or its analogue (1-penicillamine,4-threonine)oxytocin into the preoptic anterior hypothalamus caused hyperthermia in conscious rats at ambient temperatures (T_a's) of 8, 22 and 30°C. At a T_a of 8°C, the hyperthermia was solely brought about by an increase in metabolic rate. At a T_a of 22°C, the hyperthermia was brought about by both an increase in metabolism and a decrease in cutaneous temperature. At a T_a of 30°C, the hyperthermia was due to solely to decrease in cutaneous temperature. There was no change in respiratory evaporative heat loss in response to these drugs at all temperatures tested. Intrahypothalamic injection of either isoproterenol or phenylephrine also produced hyperthermia, increased metabolism and cutaneous constriction. In addition, the hyperthermia induced by intrahypothalamic injection of oxytocin or its analogue was antagonized by pretreatment with intrahypothalamic injection of sodium acetylsalicylate (an inhibitor of prostaglandin E synthetase) or yohimbine (an antagonist of alpha-adrenergic receptors) but not with propanolol (antagonist of beta-adrenergic receptors). The data indicate that a prostaglandin-adrenergic link in the hypothalamus is involved in the hyperthermia induced by oxytocin or its analogue. Furthermore, the oxytocin-induced hyperthermia was antagonized by pretreatment with a small dose of (1-penicillamine,4-threonine)oxytocin. On the other hand, the hyperthermia induced by (1-penicillamine,4-threonine)oxytocin was also antagonised by pretreatment with a small dose of oxytocin. Thus, it appears that (1-penicillamine,4-threonine)oxytocin is an anti-oxytocin analogue which inhibits the hyperthermic activity of oxytocin.     

Inverse agonist properties of N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR141716A) and 1-(2-chlorophenyl)-4-cyano-5-(4-methoxyphenyl)-1H-pyrazole-3-carboxyl ic acid phenylamide (CP-272871) for the CB(1) cannabinoid receptor

Two subtypes of cannabinoid receptors are currently recognized, CB(1), found in brain and neuronal cells, and CB(2), found in spleen and immune cells. We have characterized 1-(2-chlorophenyl)-4-cyano-5-(4-methoxyphenyl)-1H-pyrazole-3-carboxyl ic acid phenylamide (CP-272871) as a novel aryl pyrazole antagonist for the CB(1) receptor. CP-272871 competed for binding of the cannabinoid agonist (3)H-labeled (-)-3-[2-hydroxy-4-(1, 1-dimethylheptyl)-phenyl]-4-[3-hydroxypropyl]cyclohexan-1-ol ([(3)H]CP-55940) at the CB(1) receptor in rat brain membranes with a K(d) value 20-fold greater than that of N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR141716A). CP-272871 also competed for binding with the aminoalkylindole agonist (3)H-labeled (R)-(+)-[2, 3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]1, 4-benzoxazin-6-yl](1-naphthyl)methanone ([(3)H]WIN-55212-2), as well as the aryl pyrazole antagonist [(3)H]SR141716A. Inverse agonist as well as antagonist properties were observed for both SR141716A and CP-272871 in signal transduction assays in biological preparations in which the CB(1) receptor is endogenously expressed. SR141716A augmented secretin-stimulated cyclic AMP (cAMP) accumulation in intact N18TG2 neuroblastoma cells, and this response was reversed by the agonist desacetyllevonantradol. CP-272871 antagonized desacetyllevonantradol-mediated inhibition of adenylyl cyclase in N18TG2 membranes, and increased adenylyl cyclase activity in the absence of agonist. SR141716A and CP-272871 antagonized desacetyllevonantradol-stimulated (35)S-labeled guanosine-5'-O-(gamma-thio)-triphosphate ([(35)S]GTPgammaS) binding to brain membrane G-proteins, and decreased basal [(35)S]GTPgammaS binding to G-proteins. K(+) enhanced CP-272871 and SR141716A inverse agonist activity compared with Na(+) or NMDG(+) in the assay. These results demonstrated that the aryl pyrazoles SR141716A and CP-272871 behave as antagonists and as inverse agonists in G-protein-mediated signal transduction in preparations of endogenously expressed CB(1) receptors.     

Conformationally defined retinoic acid analogues. 5. Large-scale synthesis and mammary cancer chemopreventive activity for (2E,4E,6Z,8E)-8-(3',4'-dihydro-1'(2'H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,4,6-octatrienoic acid (9cUAB30)

Retinoids that activate the nuclear retinoid X receptors (RXRs) display potential for chemoprevention of breast cancer. We previously reported that 9cUAB30 (1) is an RXR-selective retinoid. To explore its in vivo chemopreventive activity, multigram quantities of 1 were needed. Here, we describe a modified synthesis that yields up to 100 g of 1. We further demonstrate that 1 is very effective in the prevention of N-methyl-N-nitrosourea induced mammary cancers in rats without signs of toxicity.     

Pharmacological properties of 1-(4-methoxybutylamino)-2-(1-4-benzodioxan-2-yl)-ethane (2802 IS)

Summary The pharmacological properties of 1-(4-methoxybutylamino)-2-hydroxy-2-(1,4-benzodioxan-2-yl) ethane (2802 IS) are described. 2802 IS when administered by vein to anesthetized dogs and cats in doses of 0.025-0.05 mg/kg lowered the blood pressure. In an instrumental reward discrimination exercise in rabbits the depressant effects of the compound were demonstrated at 0.25-0.5 mg/kg i.v. 2802 IS provokes significant changes of the cortical and subcortical electrical activity of the unanaesthesized rabbit and a dampening of the arterial pressure response to the electrical stimulation of the hypothalamus. The site of action of the central effect of the compound is discussed.This work has been supported in part by a Grant from the National Institute of Mental Health, U.S.A. (MH-07093).     

d(CH2)5Tyr(Me)-[Orn8]vasotocin, a potent oxytocin antagonist, antagonizes penile erection and yawning induced by oxytocin and apomorphine, but not by ACTH-(1-24)

Intraventricular (i.c.v.) injection of d(CH2)5-Tyr(Me)-[Orn8]vasotocin, a potent oxytocin antagonist, antagonized in a dose-dependent manner (10-100 ng) penile erection and yawning induced by the systemic injection of apomorphine (80 micrograms/kg s.c.) or by the i.c.v. injection of oxytocin (30 ng). In contrast, the oxytocin antagonist, even at the dose of 10 micrograms, did not modify penile erection and yawning induced by the i.c.v. injection of ACTH-(1-24). These results suggest that apomorphine, but not ACTH-(1-24), induce penile erection and yawning by releasing oxytocin in some brain area.