Introduction Sodium fluoride (NaF) is a bone anabolic drug ( Rigalli et al . 1992 ). However, chronic treatment with NaF produces insulin resistance (IR; Menoyo et al . 2008 , Chiba et al . 2012 ). This effect is observed in many parts of the
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Mercedes Lombarte, Brenda L Fina, Maela Lupo, Marília A Buzalaf, and Alfredo Rigalli
J Elliott, JH Scarpello, and NG Morgan
Clonal pancreatic beta-cell lines have been used widely for the study of the factors involved in the regulation of apoptosis but it has not been firmly established that the response of normal islets mirrors that found in transformed beta-cells. In the present work, the role of pertussis toxin (Ptx)-sensitive G-proteins in the control of beta-cell apoptosis was studied in isolated rat and human islets of Langerhans and compared with the clonal beta-cell line, RINm5F. Annexin-V and deoxycarboxyfluoroscein diacetate staining was used to identify viable, apoptotic and necrotic cells directly, under fluorescence illumination. Treatment of human and rat islet cells with the G-protein activator fluoride (NaF; 5 mM) caused a marked increase in apoptosis that was further potentiated in islets pretreated with Ptx. The tyrosine kinase inhibitor genistein (100 microM) also increased islet cell apoptosis and the combination of 100 microM genistein and 5 mM NaF did not lead to any diminution of the apoptotic response. This latter effect was quite different from that seen in RINm5F cells where the combination of 100 microM genistein and 5 mM NaF resulted in much less apoptosis than was observed with either agent alone. In islets treated with a lower concentration of genistein (25 microM; that did not, itself, increase cell death), the drug attenuated NaF-induced apoptosis and also blocked the enhancement mediated by Ptx. These results revealed that human (and rat) islets are equipped with a Ptx-sensitive pathway that may be regulated by tyrosine phosphorylation and is anti-apoptotic. However, they also define conditions under which marked differences in response between RINm5F cells and normal islets were observed and they suggest that care should be taken when extrapolating data obtained with clonal cell lines to the situation in normal islet cells.
E. HAVIVI and K. GUGGENHEIM
SUMMARY
Young mice were injected with 12 units of parathyroid hormone/10 g. body weight, and ash, calcium, phosphorus and uptake of radioactive calcium in their femurs were determined. Administration of the hormone resulted in a decrease of bone ash, calcium and phosphorus, and increased incorporation of radioactive calcium. These results point to the possibility that calcium turnover in bone may be increased after treatment with parathyroid hormone and that bone destruction is more intensive than formation.
Supplementation of the diet with 10–40 mg. copper or 10–50 mg. fluorine/kg. diet counteracted the effect of parathyroid hormone on bone. The highest doses of copper and fluorine used abolished the effect of the hormone completely.
The possible mechanisms of action of these elements are discussed.
G. V. GROOM, I. D. COOKE, and A. R. BOYNS
Work in this laboratory has demonstrated the ability of theophylline to stimulate the release of immunoreactive luteinizing hormone (IRLH) and follicle-stimulating hormone (IRFSH) in organ cultures of human foetal pituitary glands (Groom, Groom, Cooke & Boyns, 1971). Cyclic adenosine 3′,5′-monophosphate (cAMP), while enhancing IRFSH release, had only a minimal effect on the levels of IRLH secreted. The present study extends this work utilizing the organ culture technique and radioimmunoassay methods described previously (Groom et al. 1971).
Theophylline, a phosphodiesterase inhibitor (Robison, Butcher & Sutherland, 1968), at a concentration of 10−2 mol/l caused equal stimulation of release of both IRLH and IRFSH from the pituitaries (Table 1). In contrast, 10−2 m-cAMP, while stimulating the secretion of both IRLH and IRFSH, had a significantly greater effect on the latter (Table 1). The N 6-2′-0-dibutyryl analogue of cAMP (dbcAMP) is more potent both in vivo and in vitro, probably
S. J. Arkinstall and C. T. Jones
ABSTRACT
The regulatory factors controlling uterine activity during pregnancy remain unclear in many species. Since myometrial relaxants raise intracellular cyclic AMP, modulation of signalling pathways coupling cell-surface receptors to adenylate cyclase activation could be an important site for control. To assess the functional activity of the stimulatory GTP-binding protein Gs we have measured adenylate cyclase activation by GTP, its non-hydrolysable analogue guanosine 5′-(β-γ-imido)triphosphate (Gpp(NH)p), fluoride, forskolin and manganese in a 50 000 g membrane fraction prepared from the myometrium of non-pregnant, mid-pregnant (30–32 days) and late-pregnant (62–66 days) guinea-pigs (full term 67±2 days). While forskolin- and manganese-dependent enzyme activation was unaltered by pregnancy, maximal stimulation by Gpp(NH)p and fluoride was enhanced by up to 200%. Recovery of adenylate cyclase activity in the 50 000 g fraction was essentially constant at 20–24% of the total activity throughout pregnancy, and thus cannot explain the increases observed. Since guanine nucleotides and fluoride stimulate adenylate cyclase through activating Gs, and forskolin and manganese act at the level of the catalytic unit, these data are consistent with a pregnancy-related increase in Gs functional coupling while adenylate cyclase activity is unaltered. These observations suggest a physiological regulation of myometrial Gs activity during pregnancy which could facilitate hormonal stimulation of adenylate cyclase and contribute to uterine quiescence by increasing uterine sensitivity to relaxants.
Journal of Endocrinology (1990) 127, 15–21
I.-B. TÄLJEDAL, B. HELLMAN, and C. HELLERSTRÖM
SUMMARY
Chemical micromethods and histochemical staining were employed for studies of the enzymic hydrolysis of inosine diphosphate (IDP) and adenosine diphosphate (ADP) and the non-specific acid phosphatase activity of the endocrine pancreas from normal and cortisone-treated rats. The following observations were made:
1. Enzymic dephosphorylation of IDP and ADP was maximal at about pH 8·0. Magnesium and manganese ions enhanced the phosphate liberation, the hydrolysis of ADP being more activated than that of IDP. A marked inhibition of enzyme activity towards either substrate was produced by sodium fluoride, sodium cyanide and ethylene-diaminotetraacetate. Acid phosphatase activity was maximal at about pH 5·5, a tendency for a second activity optimum was noted at about pH 4·0. Acid phosphatase activity was markedly inhibited by sodium fluoride, tartaric acid and formaldehyde.
2. Histochemical staining revealed marked enzyme activity towards IDP and ADP in the capillaries and walls of the large blood vessels throughout the pancreas, whereas the islet cells displayed a moderate reaction. The staining intensity was the same with IDP as with ADP.
3. Cortisone administration reduced the rate of cleavage of both IDP and ADP in both the endocrine and the exocrine pancreas, but the enzymic splitting of these substrates remained unchanged in the liver. Acid phosphatase activity was not influenced in any of these tissues by the steroid treatment.
M. Zaidi, H. K. Datta, B. S. Moonga, and I. MacIntyre
ABSTRACT
Calcitonin inhibits osteoclastic bone resorption and its action involves two separate acute effects on the osteoclast, both essential to the action of the hormone: abolition of cell motility (Q) and marked cellular retraction (R). The former was mimicked by dibutyryl cyclic AMP and cholera toxin and the latter by pertussis toxin, ionomycin and increases in ambient calcium. Aluminium fluoride ions produced both Q and R effects, while lithium prevented both. In addition, calcitonin elicited a biphasic elevation of cytosolic-free calcium in single isolated osteoclasts. We propose that the action of calcitonin is mediated by at least two G proteins, one responsible for the Q effect and the other for the R effect. In addition, two second messengers, cyclic AMP and calcium, are involved. These findings may help to explain the potency of calcitonin in inhibiting bone resorption, and may allow the rational design of new therapeutic agents designed to alter osteoclast behaviour.
Journal of Endocrinology (1990) 126, 473–481
M. C. Richardson, G. M. Masson, and M. R. Sairam
ABSTRACT
The biological activity of deglycosylated human chorionic gonadotrophin (hCG) prepared by treatment of the native hormone with anhydrous hydrogen fluoride was evaluated using suspensions of dispersed cells from biopsies of human corpus luteum obtained during the luteal phase of normal menstrual cycles. A reproducible pattern of response to hCG in terms of progesterone production by luteal cells was established for a range of luteal ages. Deglycosylation of hCG led to a diminished level of maximum response to the hormone. Co-incubation of luteal cells with a level of hCG just sufficient to elicit a maximum response and increasing concentrations of deglycosylated hCG led to a progressive inhibition of the hormonal response; at a concentration of 103 ng deglycosylated hCG/ml (a tenfold excess of deglycosylated hCG over the native hormone), hCG-induced progesterone production was reduced by about 50%. Deglycosylated hCG therefore acts as a partial antagonist for the action of hCG on human luteal cells.
J. Endocr. (1984) 101, 327–332
STENER KVINNSLAND
The influence of long-term oestradiol stimulation on adenylate cyclase activity was investigated in homogenates from uterine cervices of neonatal (3-day-old) and immature (14-day-old) NMRI mice. A significant increase of enzyme activity, measured in the presence of fluoride ions (NaF), after oestradiol treatment was found in preparations from neonatal but not from those of immature female mice; this was irrespective of whether the enzyme activity was related to wet weight, amount of protein or DNA content. The enzyme activity was stimulated in vitro by NaF and 5-guanylylimidodiphosphate while isoprenalin, histamine, prolactin and oestradiol had no effect.
These results indicated an age-related difference in the effects of oestradiol in the uterine cervix of the mouse.
S. G. CROCKER, P. J. D. MILTON, and R. J. B. KING
SUMMARY
Cytoplasmic and nuclear oestradiol-17β binding sites have been measured in human endometrium obtained at different stages of the menstrual cycle and from patients with cystic hyperplasia and endometrial carcinoma. In normal endometrium both sets of sites are maximal at about the time of ovulation. The number of nuclear sites obtained by incubating endometrium with oestradiol-17β in vitro paralleled the number of available cytoplasmic sites.
Cytoplasmic and nuclear binding sites were present in cystic hyperplasia and endometrial carcinomata. There was no correlation between the degree of differentiation of the tumour and its oestradiol-17β binding capacity. All types of endometrium contained variable amounts of 8–10 S and 4–5 S cytoplasmic receptors. The proportions of these receptors were not affected by the presence of the protease inhibitor, p-phenylmethylsulphonyl fluoride.
