The in vivo effects of beta-3-receptor agonist CGP-12177 on thyroxine deiodination in cold-exposed, sympathectomized rat brown fat

Objective: The effects of the beta-3-receptor agonist CGP-12177 on thyroxine (T4) deiodination in sympathectomized (SX) interscapular brown adipose tissue (BAT) were assessed in 300 g body weight (BW) Wistar rats. Design: Seven days after SX, groups of rats were implanted s.c. with pellets containing 5 mg CGP-12177 or 5 mg norepinephrine (NE) and were immediately placed at 4°C for 24 h. Other SX groups were injected with CGP-12177 or NE 1 mg/kg BW i.p. and placed in the cold for 4 h. The latter group was injected, in addition, with prazosin 0.4 mg/100 g BW i.p. or propranolol 0.5 mg/100 g BW i.p. 15 min before and 2 h after the administration of CGP-12177 or NE. Methods: Two hours after the last injection of prazosin or propranolol, animals were killed and BAT was removed, homogenized and centrifuged at 500g for 10min at 4°C. The infranatants were incubated during 60min in the presence of dithiothreitol and 1 μCi [125I]T4. Aliquots were chromatographed on paper for the measurement of [125I]T4 and its deiodinated subproducts. Results: CGP-12177 restored normal T4 deiodination in SX BAT from both groups, but NE was slightly more effective. Propranolol, although not prazosin, blocked the CGP-12177 effects. Contrariwise, the NE-induced rise in deiodination was blocked by prazosin and to a lesser extent by propranolol. Conclusions: The results indicate that CGP-12177 stimulated the in vivo activation of 5'-deiodinase type II activity predominantly via beta-3-receptor, without participation of alpha-1-receptors.Fil: Hofer, Dietmar. Karl-Franzens-Universität Graz; AustriaFil: Raices, Marilina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular ; ArgentinaFil: Schauenstein, Konrad. Karl-Franzens-Universität Graz; AustriaFil: Porta, Sepp. Karl-Franzens-Universität Graz; AustriaFil: Korsatko, Wolfgang. Karl-Franzens-Universität Graz; AustriaFil: Hagmüller, Karl. Karl-Franzens-Universität Graz; AustriaFil: Zaninovich, Angel Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular ; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín; Argentin

lin–Sca-1+ Cells and Age-Dependent Changes of Their Proliferation Potential Are Reliant on Mesenchymal Stromal Cells and Are Leukemia Inhibitory Factor Dependent

Aging as a process is paralleled by a variety of hematological alterations. Characteristic features are a diminished homeostatic control of blood cell production and a decline in immune functions. It is generally accepted that stromal cells play a basal role in hematopoiesis by providing survival and differentiation signals, by secreting cytokines, or through direct contact with hematopoietic stem cells, thereby supporting the generation and replenishment of hematopoietic progenitor cells (HPC). Here we demonstrated that HPC-related colony formation is positively influenced by mesenchymal stromal cells (MSCs) when grown in co-culture, in particular regarding the number of primary granulocyte/macrophage colony-forming units as well as with respect to the average size of the formed colonies. These effects were more pronounced when the MSCs originated from young donors than from old ones. Because leukemia inhibitory factor (LIF) plays an important role during hematopoiesis, properties of lin-- Sca-1+ cells and MSCs derived from LIF-deficient mice (LIF--/--) were determined both ex vivo and in vitro. LIF--/-- animals contain a significantly reduced number of lin-- Sca-1+ cells, nevertheless the replating capacity of LIF--/-- HPCs was found to be generally unchanged when compared to those from LIF+/+ animals. However, when cocultured with MSCs, LIF--/-- lin-- Sca-1+ cells exhibited comparable characteristics to HPCs derived from old wild-type animals