RESUMEN
Using selective receptor's agonist and antagonists we show that mouse white fat cells express alpha1A-, alpha2-adrenergic receptors, which activation with noradrenaline is capable of causing calcium responses different by formation mechanism. Adipocyte's calcium responses to alpha1-adrenoreceptor agonists are caused by alpha1A-type adrenoreceptor and suppressed by inhibitors of PLC-dependent pathway. Calcium responses to alpha2-adrenoreceptors agonists are realized only in the presence of more than 200 microM of L-arginine and suppressed by inhibitors of NOS-PKG-RyR pathway. The incubation of cells with L-arginine creates conditions for switching on the signal pathway with participation of eNOS --> NO --> sGC --> cGMP --> PKG --> CD38 --> RyR --> Ca2+ and for switching of the PLC - IP3R-dependent pathway. Adipocyte's calcium response to L-arginine represents a sharp impulse of the big amplitude and is mediated by alpha2-adrenoreceptors. L-arginine activating alpha2-adrenoreceptors and being the substrate of eNOS, realizes two functions in this pathway.
Asunto(s)
Adipocitos/efectos de los fármacos , Agonistas Adrenérgicos/farmacología , Antagonistas Adrenérgicos/farmacología , Señalización del Calcio/efectos de los fármacos , Calcio/metabolismo , Norepinefrina/farmacología , Receptores Adrenérgicos alfa 2/metabolismo , Adipocitos/citología , Adipocitos/metabolismo , Tejido Adiposo Blanco/citología , Tejido Adiposo Blanco/efectos de los fármacos , Tejido Adiposo Blanco/metabolismo , Animales , Arginina/metabolismo , Arginina/farmacología , Señalización del Calcio/fisiología , Diferenciación Celular , Inhibidores Enzimáticos/farmacología , Imidazoles/farmacología , Ratones , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo III/metabolismo , Fenilefrina/farmacología , Cultivo Primario de Células , Receptores Adrenérgicos alfa 1/metabolismo , Tetrahidronaftalenos/farmacología , Fosfolipasas de Tipo C/metabolismoRESUMEN
Thermogenic capability of brown adipose tissue is controlled by norepinephrine. Interaction of norepinephrine with adipocyte at- and P3-adrenergic receptors results in the increase of Ca2+ and cAMP concentrations. The [Ca2+]i changes initiated by norepinephrine and selective agonists of alpha1- and beta-adrenergic receptors, cirazolin and isoproterenol, were recorded in single cells of primary culture on the 1st, 3rd and 6th days in vitro. On the first day, isoproterenol-induced [Ca2+]i changes as compared to cirazolin-induced ones were characterized by greater amplitude and lesser impulse duration over the entire range of physiological concentrations used. These differences were negligible after 3 days and kinetic differences were practically absent after 6 days of cultivation. The agonist-induced [Ca2+]i changes in proliferating and differentiated cells differed significantly: in the process of cell growth in culture, the amplitude of calcium response increased, the duration of impulse signal decreased and the sensitivity to adrenergic agonists increased. The Ca2+ store in endoplasmic reticulum increased during the cell growth and development in culture, according to thapsigargin-induced Ca2+ response amplitude increase in Ca2+ free medium. The rate of Ca2+ pumping out of cell characterizing PMCA-activity also increased.