A postsynaptic α, 2-receptor: The alpha-adrenergic receptor of hamster white fat cells

Summary The effects of selected -agonists and -antagonists on theophylline-induced lipolysis were investigate in isolated hamster white fat cells ₂-Agonists (tramazoline, clonidine) inhibited theophylline-induced lipolysis while an ₂-agonist (methoxamine) was without any effect. The inhibitory effect of ₂-agonists was suppressed by yohimbine (₂-antagonist), whereas ₂-antagonists were inefficient. This result implies that the -adrenergic receptor of hamster fat cells is of the ₂-type, although located postsynaptically.Acknowledgments. This work was supported by grants from CNRS (ERA 412) and DGRST (grant No. 787 1078). We thank M. Dauzats for excellent technical assistance. We thank Prof. H. Schmitt for tramazoline and AR-C 239 and for helpful discussion.     

Effect of prostaglandin F2α on the secretion of pancreatic juice induced by secretin and by dopamine

Zusammenfassung Die Wirksamkeit von Prostaglandin F₂ (PGF₂) auf die exokrine Pankreassekretion wurde an einem mit Blut perfundiereten Pankreas-Präparat des Hundes untersucht. PGF₂ (100 g) hemmte die durch Sekretin stimuliete, aber nicht die durch Dopamin stimulierte Sekretion.     

G-protein signaling: back to the future

Heterotrimeric G-proteins are intracellular partners of G-protein-coupled receptors (GPCRs). GPCRs act on inactive G·GDP/G heterotrimers to promote GDP release and GTP binding, resulting in liberation of G from G. G·GTP and G target effectors including adenylyl cyclases, phospholipases and ion channels. Signaling is terminated by intrinsic GTPase activity of G and heterotrimer reformation – a cycle accelerated by regulators of G-protein signaling (RGS proteins). Recent studies have identified several unconventional G-protein signaling pathways that diverge from this standard model. Whereas phospholipase C (PLC) is activated by G_q and G, novel PLC isoforms are regulated by both heterotrimeric and Ras-superfamily G-proteins. An Arabidopsis protein has been discovered containing both GPCR and RGS domains within the same protein. Most surprisingly, a receptor-independent G nucleotide cycle that regulates cell division has been delineated in both Caenorhabditis elegans and Drosophila melanogaster. Here, we revisit classical heterotrimeric G-protein signaling and explore these new, non-canonical G-protein signaling pathways.Received 21 October 2004; received after revision 20 November 2004; accepted 30 November 2004     

Orally administered melatonin stimulates the 3α/β-hydroxysteroid oxidoreductase but not the 5α-reductase in the ventral prostate and seminal vesicles of pinealectomized rats

Summary Pinealectomized rats were treated orally with melatonin (MEL) for 14 days. Prostates and seminal vesicles were investigated for the activity of the 4-3-ketosteroid-5-oxidoreductase (5-R) and of the 3/-hydroxysteroid-oxidoreductase (3-HSO). The activity of the 3a-HSO was significantly stimulated (p<0.01, Friedman test) when compared to controls. The activity of the 5-R did not change significantly.This work was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 34 (Endokrinologie).     

Metabolism in Porifera. IX. Studies on the biological conversion of cholesterol into 19-nor-cholestanol by the spongeAxinella polypoides

Summary The conversion of cholesterol into 19-nor-5-cholestan-3-ol by the spongeAxinella polypoides involves a partial loss (40%) of the 3-hydrogen atom; moreover administration to the sponge of [4-¹⁴C]cholesterol tritiated at C-4 and C-7 showed that the 4- and 7-hydrogen atoms are retained in this conversion. A competitive uptake experiment, [4-¹⁴C]cholesterol vs. [7-³H₂]5-cholestanol, showed that the sponge utilized exclusively cholesterol for the production of 19-nor-5-cholestan-3-ol.Part of this work has been presented at the Nato Conference on Marine Natural Products (Jersey, Great Britain, October, 1976).-This contribution is part of the Programma finalizzato Oceanografia e Fondi marini-sottoprogetto Risorse biologiche C.N.R. Italy.     

Ethanol and opioid receptor signalling

Summary Ethanol may modulate endogenous opioid systems by disrupting opioid receptor signalling. Low concentrations of ethanol slightly potentiate -opioid receptor binding by increasing receptor B_max, and, in some cases, chronic ethanol exposure decreases the density or affinity of the -opioid receptors. By contrast, high concentrations of ethanol acutely decrease -opioid receptor binding by decreasing receptor affinity, whereas chronic exposure of animals and neuronal cell lines to lower concentrations of ethanol leads to possibly adaptive increases in the density or affinity of the -opioid receptors. In the neuronal cell line NG108-15, ethanol does not up-regulate the -opioid receptor by blocking receptor degradation or endocytosis, but protein synthesis is required for this response. Up-regulation of the -opioid receptor renders ethanol-treated NG108-15 cells 3.5-fold more sensitive to opioid inhibition of adenylyl cyclase. Long-term treatment with ethanol also increases maximal opioid inhibition in NG108-15 cells, possibly by decreasing levels of G_s and its mRNA. Ethanol differentially modulates signal transduction proteins in three additional neuronal cell lines, N18TG2, N4TG1, and N1E-115. Ethanol-treated N18TG2 cells show the least up-regulation of the -opioid receptor, little heterologous desensitization of adenylyl cyclase, and no changes in G_s or G_i. By contrast, ethanol-treated N1E-115 cells show the largest up-regulation of the -opioid receptor, the most heterologous desensitization of adenylyl cyclase, and concentration-dependent decreases in G_s and increases in G_i. Further analysis of these related neuronal cell lines may help to identify the molecular elements that endow some, but not all, neuronal cells with the capacity to adapt to ethanol.     

Synthese von 22,26-Imino-cholestan-Derivaten

Summary 3, 16-diacetoxy-5-pregnane-20-one and the analogue pregn-5-ene derivative have been converted into (22R, 25R)-22, 26-imino-5-cholestane-3, 16-diol. The configuration at C-22 and C-25 was determined by transformation into the known (22R, 25R)-5-solanidane-3-one. Application of the Ruschig method led to (25R)-22,26-imino-5-cholest-22(N)-ene-3, 16-diol.

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Solanum-Alkaloide. XVI. Mitteilung. — XV. Mitteilung:K. Schreiber undH. Ripperger, Tetrahedron Letters Nr.27, 9 (1960).     

Wirkung von 6β-Methoxy-9β,10α-pregna-4,6-dien-3,20-dion

Summary 6-Methoxy-9,10 -pregna-4,6-diene-3,20-dione inhibites the ⁴-3-oxosteroid-5-reduction in microsomes and the ⁴-3-oxosteroid-5-reduction in the soluble fraction of male rat liver. The 3- and 3-hydroxysteroid dehydrogenase are not inhibited by this substance.

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Diese Arbeit wurde von der Firma Hoffmann-La Roche, Basel, unterstützt.     

1,2-Methylen-19-nor-17α-acetoxy-progesteron

Summary The syntheses and structure-determinations of 1, 22- and 1, 2-methylene-19-nor-17-acetoxy-progesterones described prove that there is no influence of the angular C₁₀-methylgroup on the steric course of theCourey-methylenations of ¹-3-keto-steroids.     

Antagonism of V2-receptor effect of antidiuretic hormone by atrial natriuretic peptide in man

Summary Human -atrial natriuretic peptide (h-ANP) makes the urine of dehydrated volunteers hypotonic to plasma despite high circulating concentrations of antidiuretic hormone. Urinary dilution with h-ANP also occurs in subjects receiving indomethacin. Therefore, h-ANP antagonises effects of antidiuretic hormone on distal tubular V₂-receptors in man, probably without involving prostaglandins.     

Gender- and site-related effects on lipolytic capacity of rat white adipose tissue

Gender- and site-related differences in the lipolytic capacity, at the different steps of the adrenergic pathway, in gonadal and inguinal white adipose tissue (WAT), were assessed by studying _2A-adrenergic receptor (AR), ₃-AR and hormone-sensitive lipase (HSL) protein levels, and by determining the lipolytic response to different agents. Gonadal WAT showed a lower _2A/₃-AR ratio, a greater lipolytic capacity in response to AR agonists, and higher HSL activity and protein levels than inguinal WAT. In female rats, we found greater _2A-AR protein levels and _2A/₃-AR ratio compared to their male counterparts, but, on the other hand, a higher lipolytic response to -AR agonists and a greater lipolytic capacity at the postreceptor level, including a more activated HSL protein. Thus, the lipolytic capacity was clearly higher in gonadal than in inguinal WAT, at the different steps of the adrenergic pathway studied. Moreover, in both tissues, females showed a greater inhibition of lipolysis via ₂-AR, which was counteracted by the higher lipolytic capacity at the postreceptor level.Received 1 April 2003; received after revision 11 June 2003; accepted 23 June 2003     

Axillary 5α-androst-16-en-3-one in men and women: Relationships with olfactory acuity to odorous 16-androstenes

Summary Axillary 5-androst-16-en-3-one (5-androstenone) levels were found to be significantly higher in men than in women but do not vary between left and right axillae, are not related to age, handedness or degree of hirsutism (in women) nor to anosmia to this steroid. In men (but not in women), levels are related linearly to axillary cholesterol concentrations but not to squalene. Olfactory thresholds for 5-androstenone varied widely, the lowest recorded being 0.2 ppb, but there was no difference in thresholds between men and women. Women (70%) found the smell repellant but anosmia did not differ greatly between men and women (9–20%). Anosmia to the smell of 5-androst-16-en-3-ol was most marked in women (90%) rather than in men (45%). Axillary 5-androstenone values were generally consistent with the musky or strong smells of male axillary extracts, compared with the sweet smell of those from female subjects.Supported by the Herbert Dunhill Trust.     

Exchange of tritium from randomly tritiated taurocholate by microbial bile salt oxidoreductases

Summary Tritium distribution on randomly labelled taurocholate (TC) was estimated at 28%, 4%, 1% and <0.5% on the hydrogens opposite the 3-, 7- and 12-OH groups and taurine moiety respectively. Anomalously,C. perfringens 3-hydroxysteroid dehydrogenase (3-HSDH) catalyzed tritium loss of 36% on formation of 7-, 12-dihydroxy-3-keto-5-cholanoate, implying additional losses of tritium at other sites by this enzyme.This work is supported by the National Cancer Institute.     

The molecular structure of the benzilic acid rearrangement product of 3α, 17β-diacetoxy-11-hydroxy-12-oxo-5β-androst-9(11)-ene

Zusammenfassung Die Struktur desp-Brombenzoates des Benzilsäureumlagerungsproduktes von 3, 17-Diacetoxy-11-hydroxy-12-oxo-5-9(11)-androsten wurde durch dreidimensionale Röntgenstrukturanalyse eines Einkristalls als 3-p-Brombenzoat des 11-Carboxy-3, 11, 17-trihydroxy-13-C-nor-5-androstan 11a, 17-Laktons erkannt.     

Deuterium isotope effects in the ninhydrin reaction of primary amines

Summary The rate of development of Ruhemann's purple in the ninhydrin reaction of two deuterated primary amines, -d₂-p-tyramine and -d₂--phenylethylamine, is significantly reduced It appears to be a primary isotope effect and indicates that the cleavage of the carbon-hydrogen bond at the -position is involved in the rate-determining step of the color reaction.Acknowledgements. We thank Dr A.A. Boulton for his advice and encouragement and the Canadian Medical Research Councel and Saskatchewan Health for their continuing financial support.     

Retroaldol transformations in the westphalen diol series

Zusammenfassung Durch Behandlung mit Kalilauge erleidet 5-methyl-19-norcholestan-9, 10-diol-3, 6-dione eine Retroaldolisomerisierung unter Bildung des 10-Hydroxy-Isomers. Letzteres wurde als Hemiketalderivat isoliert. Bei drastischer Behandlung mit Alkali gehen beide Isomere in ein Anthrasteroid über.     

Inhibition of lung carcinoma cell growth by high density lipoprotein-associated α-tocopheryl-succinate

-Tocopheryl-succinate (TS) is a synthetic, anti-neoplastic derivative of -tocopherol. Here we studied the effects of free and high-density lipoprotein subclass 3 (HDL₃)-associated TS on the growth of human (A549) and mouse Lewis (LL2) lung carcinoma cells. Both free and HDL3-associated TS inhibited A549 growth in a time- and concentration-dependent manner. Treatment of A549 cells with TS-enriched HDL3 led to DNA fragmentation and a time-dependent decrease in immunoreactivity of poly(ADP-ribose)polymerase. Uptake experiments revealed a high capacity for selective TS uptake in excess of holoparticle endocytosis. Overexpression of scavenger receptor class B, type I (SR-BI), the prime receptor mediating selective lipid uptake, in A549 cells resulted in significantly increased selective TS uptake, a finding associated with complete cellular growth arrest. The present in vitro findings were verified in an in vivo model: tumor inoculation in C57BL6 was performed with either wild-type, -galactosidase- or SR-BI-overexpressing LL2 cells. After tumor inoculation, the animals received six consecutive intravenous injections of TS. This experimental setup resulted in significantly reduced tumor burden in animals that were inoculated with SR-BI-overexpressing LL2 cells but not in animals inoculated with wild-type or -galactocidase-transfected cells. Based on our in vitro and in vivo findings, we propose that SR-BI could provide a novel route for HDL₃-mediated drug delivery of anti-neoplastic drugs.Received 8 March 2004; received after revision 7 April 2004; accepted 26 April 2004     

Hydra vulgaris ω10-lipoxygenase is used in vivo to synthesize new α-linolenic acid metabolites

Previous studies conducted in cytosolic extracts of the freshwater hydrozoanHydra vulgaris led to the finding of an abundant 11(R)-lipoxygenase catalyzing the peroxidation of polyunsaturated fatty acid (PUFAs) on the tenth carbon atom from the aliphatic end (10 peroxidation). Here we describe experiments aimed at identifying the actual metabolites generated in vivo by such enzymic activity. Homogenates ofH. vulgaris polyps were analyzed by HPLC. This showed the presence of three major components chromatographically identical to three metabolites obtained when incubating the homogenates with exogenous -linolenic acid (-LA). The presence, in extracts of polyps prelabelled with [¹⁴C]--linolenic acid, of radioactive metabolites displaying the same chromatographic properties, substantiated the hypothesis that the natural products isolated in vivo are derived from -LA. Gas chromatographic analyses revealed that this was the most abundant PUFA in both free and phosphoglyceride-bound fatty acid pools. [¹H]-NMR analysis of the endogenous substances, carried out in comparison with products obtained from exogenously incubated -LA, indicated that their structures were those of 9-hydroxy-, 9-hydroperoxy- and 9-keto-octadeca-10E-12Z-15Z-trienoic acids (9--HOTrE,-HPOTrE and-KOTrE).Hydra homogenates transformed 9--HPOTrE partly into 9--HOTrE and partly into 9--KOTrE. Chiral phase HPLC conducted on 9--HOTrE established that this metabolite was composed mostly of theR anantiomer. These observations, and the finding that the presence of exogenous arachidonic acid in incubated homogenates significantly reduces the production of -LA metabolites, provide strong evidence that these compounds are produced by an enzymic activity identical to the previously-describedH. vulgaris (R)-10-lipoxygenase. Further experiments suggested that -LA, acting as the native substrate for this enzyme, is mainly esterified on the 2 position ofHydra phosphoglycerides, and that the production of the -LA metabolites described here for the first time from natural sources, can be potentially enhanced in vivo by stimuli activating phospholipase A₂.     

Different effects of D-glucose anomers for respiration of bacterial germinated spores

Summary Effects of - or -D-glucose on the respiration of germinated spores (only germinated spores not including swollen spores and elongated spores) ofBacillus subtilis andB. megaterium were studied. In our conditions, net amount of oxygen consumed by 10¹⁰ germinated spores ofB. subtilis per min after addition of - or -D-glucose was 1.6 g or 6.6 g (/=4.13), while that byB. megaterium was 4.5 g or 6.8 g (/=1.51), respectively. However, the net amounts of oxygen consumed by 10¹⁰ vegetative cells per min after addition of - or -D-glucose were identical, forB. subtilis in both cases 443.0 g and forB. megaterium in both cases 604.4 g.     

Effects of injury on the concentration ofα 1 andα 2 in the plasmas of male and female rats

Summary The effects of injury on the concentration of ₁-macroglobulin and ₂-macroglobulin in the plasmas of male and female rats has been investigated. At 5 days after injury to the male rats the ₁-macroglobulin concentration increased to 131% of its preinjury value. The ₂-macroglobulin concentration increased more rapidly to a maximum of 86 times its initial value. In the female rats ₂-macroglobulin increased only slightly and ₁-macroglobulin not at all.