Protein Kinase C (PKC) alpha and epsilon isoforms are involved in rat lactotroph cell proliferation induced by insulin-like growth factor I (IGF-1) in vitro

GUTIÉRREZ S.; PETITI J. P.; DE PAUL A.L,; AOKI A.; ORGNERO E.; TORRES A.I.

Campinas, Brasil

Congreso; XII Congreso de la Sociedad Brasilera de Biología Celular y IX Congreso de la Sociedad Iberoamericana de Biología Celular; 2004

Sociedad Brasilera de Biología Celular

It is well known that IGF-I promotes pituitary cell proliferation mediated by tyrosine-kinase receptors, however little is known about IGF-I signal transduction pathways leading to lactotroph proliferation. The present study was designed to clarify the role of protein kinase C alpha and epsilon isoforms, in the proliferative process of lactotroph cells in vitro.             Pituitary cell cultures from female Wistar rats were treated for 72h with IGF-I (30ng/ml). In parallel, some wells were co-incubated with IGF-I and genistein (25mM), a tyrosine-kinase specific inhibitor. Lactotroph cell proliferation was assessed by double immunolabelling of bromodeoxyuridine and prolactin. PKC alpha and epsilon isoforms and extracellular signal-regulated protein kinases 1 and 2 activated (ERK1/2) expression was determined by western blot. Ultrastructure of IGF-1 treated lactotrophs was also analysed. Statistical analysis consisted in an ANOVA/Tukey-test.             A significant increment of lactotroph cells proliferation was observed with IGF-1 treatment. Administration of IGF-1/genistein caused a remarkable diminution (p<0.001) on mitogenic activity respect to IGF-1 treatment. IGF-I stimulation induced an augmentation of PKC alpha, epsilon and ERK-1/2-activated expression, while co-incubation with IGF-1/genistein showed lower levels of these enzymes.             Our results suggest that PKC alpha and epsilon are involved in the signalling pathway mediating mitogenic action of IGF-1 on rat lactotroph cells by activation of ERK-1/2 cascade.