RESUMO
Tail fin regression can be induced in anuran amphibians with L-thyroxine (T4). This regression can be antagonized with prolactin (PRL). Previous work had suggested that protein kinase C (PKC) was involved in PRL action. To address this issue further, the effect of a potent and selective inhibitor of protein kinase C on in vitro tail fin regression was investigated. T4-induced regression of tail fin pieces from Rana pipiens tadpoles could be antagonized by adding PRL or the PKC inhibitor H-7 to the medium. H-7 inhibited fin regression in a dose-dependent manner, with a half-maximal effective concentration of about 10(-5) M. The H-7 analogue, HA-1004 (which is not a selective inhibitor of PKC), was without effect. These results suggest a possible role for PKC in tail fin regression and may be useful in elucidating the antimetamorphic action of PRL.
Assuntos
Metamorfose Biológica/fisiologia , Proteína Quinase C/fisiologia , Rana pipiens/fisiologia , Sulfonamidas , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina , Animais , Relação Dose-Resposta a Droga , Técnicas In Vitro , Isoquinolinas/farmacologia , Metamorfose Biológica/efeitos dos fármacos , Piperazinas/farmacologia , Prolactina/farmacologia , Proteína Quinase C/antagonistas & inibidores , Tiroxina/farmacologiaRESUMO
The present study has examined the effects of adenosine A1 receptors on second messenger processes in GH3 cells. A1 receptors are present which are shown to inhibit adenylate cyclase in a GTP-requiring manner. Hormone (VIP) stimulation is also absolutely required for the observation of inhibition. Adenosine A1 receptor analogues also inhibit TRH-stimulated [Ca2+]i-mobilization in GH3 cells. Both effects of the adenosine receptor agonists are apparently mediated by pertussis toxin substrates, of which there are two--41,000 and 40,000 daltons respectively--in these cells. Somatostatin exerts analogous effects to the adenosine agonists in GH3 cells. Thus it may turn out that a general property of 'cyclase inhibitory receptors' is also to inhibit [Ca2+]i-mobilization in the same cells, when such mechanisms are present.
Assuntos
Adenilil Ciclases/metabolismo , Canais de Cálcio/metabolismo , Proteínas de Ligação ao GTP/fisiologia , Receptores Purinérgicos/fisiologia , Hormônio Liberador de Tireotropina/fisiologia , Toxina Adenilato Ciclase , Animais , Linhagem Celular , Membrana Celular/enzimologia , Proteínas de Ligação ao GTP/efeitos dos fármacos , Toxina Pertussis , Fenilisopropiladenosina/farmacologia , Somatostatina/fisiologia , Peptídeo Intestinal Vasoativo/fisiologia , Fatores de Virulência de Bordetella/farmacologiaRESUMO
The accumulation of inositol-1-phosphate in rat striatal slices was inhibited by the adenosine analogues 5'-N-ethylcarboxamide-adenosine and N6-phenylisopropyladenosine. Maximal inhibition (approximately 20%) was achieved by micromolar concentrations of either compound. Both basal and stimulated values could be inhibited, and the inhibition was reversible by the adenosine receptor antagonist 8-phenyltheophylline (10 microM). The results suggest that adenosine may exert a tonic inhibitory influence on inositol phospholipid-derived second messenger production in the striatum in vivo.
