Vasopressin and angiotensin induce inositol lipid breakdown in rat adenohypophysial cells in primary culture

Adenohypophysial cells from female Wistar rats were dispersed and maintained for 4 days in primary culture in the presence of [3H]myoinositol. The effects of several releasing hormones, corticotropin-releasing factor (CRF), arginine vasopressin (AVP), angiotensin II (A II), thyrotropin-releasing hormone (TRH), and luteinizing hormone-releasing hormone (LHRH) on the liberation of labelled inositol phosphate (InsP), inositol-bisphosphate (InsP2), and inositol-trisphosphate (InsP3) from prelabelled inositol lipids were tested alone and in combination. Of the corticotropin (ACTH) secretagogues tested, AVP and A II produced a dose-dependent increase in inositol phosphate accumulation. CRF was inactive. The ED50 values of about 1 nM for both AVP and A II were close to the corresponding dissociation constants for binding to pituitary membranes: and, in the case of A II, close to the ED50 for A II-induced inhibition of pituitary membrane adenylate cyclase. The responses to A II and AVP could be inhibited by [Sar1,Ile8]A II and the AVP antagonist d(Et2)-VAVP, respectively. The magnitude of the maximal effect of AVP on accumulation of inositol phosphates was small (25% increase over basal value) suggesting that this effect was restricted to a minor subpopulation of pituitary cells (probably corticotrophes). CRF did not potentiate AVP-induced inositol phosphates accumulation. Maximal A II-induced increase in inositol phosphates accumulation represented 150% of the basal value and was partially additive with that of TRH suggesting that lactotrophes represent the main A II-sensitive subpopulation.     

Characterization of specific V1a vasopressin-binding sites on a rat mammary-tumour-cell line.

WRK 1, a cloned cell line derived from a rat mammary tumour, carries specific vasopressin-binding sites. Specific binding of 2-tyrosine-3H-labelled [8-lysine]vasopressin ([3H]vasopressin) was time-dependent, saturable and reversible. Scatchard-plot analysis of hormone binding indicated the presence of a single class of receptors with an equilibrium dissociation constant of 12.7 +/- 0.2 nM. The maximal binding capacity was 75 +/- 6 fmol/10(6) cells, which corresponds to approx. 45,000 sites per cell. Oxytocin and a highly potent oxytocin analogue were able to inhibit completely [3H]vasopressin binding, but, in this respect, they were far less potent than vasopressin. This clearly demonstrates the vasopressinergic nature of this receptor. Pharmacological studies using a series of 14 vasopressin or oxytocin analogues indicated that the ligand selectivity of the vasopressin receptor found on WRK 1 cells resembles that of the rat hepatocyte. This signifies that this vasopressin receptor is of the V1a subtype. This conclusion was confirmed by the observation that vasopressin did not influence the production of intracellular cyclic AMP in WRK 1 cells.     

Cellular thorn-like projections in human endocervical epithelium. Preliminary scanning electron-microscopic study.

By means of scanning electron-microscopic investigations, thorn-like projections (TLP) were observed in the cilio-secretory epithelium of the ventral surface of the human endocervix. These projections, which seem to be characteristic of a new cell type, were seen at different stages of the menstrual cycle (days 8, 14 and 21) in 4 apparently healthy fertile women. Striking differences in length, with a maximum size at midcycle, suggest an evolutive process throughout the menstrual cycle. The origin and possible physiological role of TLP in the reproductive process are discussed.     

Magnesium-induced inner membrane aggregation in heart mitochondria: prevention and reversal by carboxyatractyloside and bongkrekic acid

Mg(2+) at an optimal concentration of 2mM (ph 6.5) induces large increases (up to 30 percent) in the optical density of bovine heart mitochondria incubated under conditions of low ionic strength (< approx. 0.01). The increases are associated with aggregation (sticking together) of the inner membranes and are little affected by changes in the energy status of the mitochondria. Virtually all of a number of other polyvalent cations tested and Ag(+) induce increases in mitochondrial optical density similar to those induced by Mg(2+), their approximate order of concentration effectiveness in respect to Mg(2+) being: La(3+) > Pb(2+) = Cu(2+) > Cd(2+) > Zn(2+) > Ag(+) > Mn(2+) > Ca(2+) > Mg(2+). With the exception of Mg(2+), all of these cations appear to induce swelling of the mitochondria concomitant with inner membrane aggregation. The inhibitors of the adenine nucleotide transport reaction carboxyatratyloside and bongkrekic acid are capable of preventing and reversing Mg(2+)-induced aggregation at the same low concentration required for complete inhibition of phosphorylating respiration, suggesting that they inhibit the aggregation by binding to the adenine nucleotide carrier. The findings are interpreted to indicate (a) that the inner mitochondrial membrane is normally prevented from aggregating by virtue of its net negative outer surface change, (b) that the cations induce the membrane to aggregate by binding at its outer surface, decreasing the net negative charge, and (c) that carboxyatractyloside and bongkrekic acid inhibit the aggregation by binding to the outer surface of the membrane, increasing the net negative charge.     

Size of vasopressin receptors from rat liver and kidney

Specific vasopressin receptors in rat liver membranes were recently characterized [Cantau et al., Journal of Receptors Research, in the press]. They differ from the receptors characterized earlier in kidney membranes as regards coupling with adenylate cyclase and specificity towards vasopressin structural analogues [Rajerison et al. (1974) J. Biol. Chem. 249, 6390-6400; Butlen et al. (1978) Mol. Pharmacol. 14, 1006-1017]. The object of the present work was to see whether these differences reflect a difference in the molecular size of liver and kidney vasopresin receptors. For this purpose, rat liver and kidney membranes were incubated with [3H]vasopressin and solubilized with Triton X-100 (0.3%). The properties of the macromolecular components of soluble extracts to which labelled vasopressin remained bound were observed to resemble those of the intact membrane receptors as regards binding reversibility at 30-37 degrees C and sensitivity to guanyl nucleotides. The hydrodynamic parameters of the soluble hormone-receptor complexes were estimated from Utrogel column filtration experiments and from sucrose density gradient ultracentrifugation experiments. The following values were obtained for liver and kidney receptors respectively: Stokes' radii: 5.4 and 5.6 nm; standard sedimentation coefficients: 3.7 and 3.7 S; partial specific volumes: 0.75 and 0.78 ml x g-1; molecular weight: 83000 and 80000. These results indicate that the marked functional differences between liver and kidney receptors are not accompanied by appreciable differences in molecular size.     

Anti-leukemia Activity of 7-hydroxy-2-substituted-methyl-5 H -oxazolo[3,2- a] pyrimidin-5-one Derivatives

The synthesis of new 7-hydroxy-2-substituted-methyl-5 H -oxazolo[3,2- a] pyrimidin-5-ones derivatives, designed as structural bicyclic analogues of the iron chelator deferiprone, is described. They were tested for their ability to inhibit proliferation in human Bcr-Abl + leukemia cells.     

Design,synthesis, and antiprotozoal evaluation of new 2,4-bis[(substituted-aminomethyl)phenyl]quinoline, 1,3-bis[(substituted-aminomethyl)phenyl]isoquinoline and 2,4-bis[(substituted-aminomethyl)phenyl]quinazoline derivatives

Abstract

A series of new 2,4-bis[(substituted-aminomethyl)phenyl]quinoline, 1,3-bis[(substituted-aminomethyl)phenyl]isoquinoline, and 2,4-bis[(substituted-aminomethyl)phenyl]quinazoline derivatives was designed, synthesised, and evaluated in?vitro against three protozoan parasites (Plasmodium falciparum, Leishmania donovani, and Trypanosoma brucei brucei). Biological results showed antiprotozoal activity with IC₅₀ values in the µM range. In addition, the in?vitro cytotoxicity of these original molecules was assessed with human HepG2 cells. The quinoline 1c was identified as the most potent antimalarial candidate with a ratio of cytotoxic to antiparasitic activities of 97 against the P. falciparum CQ-sensitive strain 3D7. The quinazoline 3h was also identified as the most potent trypanosomal candidate with a selectivity index (SI) of 43 on T. brucei brucei strain. Moreover, as the telomeres of the parasites P. falciparum and Trypanosoma are possible targets of this kind of nitrogen heterocyclic compounds, we have also investigated stabilisation of the Plasmodium and Trypanosoma telomeric G-quadruplexes by our best compounds through FRET melting assays.