Prolactin-Signal Transduction in Neonatal Rat Pancreatic Islets and Interaction with the Insulin-Signaling Pathway

M. E. C. Amaral; M. Ueno; J. B. Carvalheira; E. M. Carneiro; L. A. Velloso; M. J. A. Saad; A. C. Boschero

doi:10.1055/s-2003-41303

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2003; 35(5): 282-289
DOI: 10.1055/s-2003-41303

Original Basic

Prolactin-Signal Transduction in Neonatal Rat Pancreatic Islets and Interaction with the Insulin-Signaling Pathway

M. E. C. Amaral ¹ , M. Ueno ² , J. B. Carvalheira ² , E. M. Carneiro ¹ , L. A. Velloso ² , M. J. A. Saad ² , A. C. Boschero ¹

¹ Departamento de Fisiologia e Biofísica and
² Departamento de Clínica Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, Brasil

Abstract

During pregnancy, pancreatic islets undergo structural and functional changes in response to an increased demand for insulin. Different hormones, especially placental lactogens, mediate these adaptive changes. Prolactin (PRL) mainly exerts its biological effects by activation of the JAK2/STAT5 pathway. PRL also stimulates some biological effects via activation of IRS-1, IRS-2, PI 3-kinase, and MAPK in different cell lines. Since IRS-2 is important for the maintenance of pancreatic islet cell mass, we investigated whether PRL affects insulin-signaling pathways in neonatal rat islets. PRL significantly potentiated glucose-induced insulin secretion in islets cultured for 7 days. This effect was blocked by the specific PI 3-kinase inhibitor wortmannin. To determine possible effects of PRL on insulin-signaling pathways, fresh islets were incubated with or without the hormone for 5 or 15 min. Immunoprecipitation and immunoblotting with specific antibodies showed that PRL induced a dose-dependent IRS-1 and IRS-2 phosphorylation compared to control islets. PRL-induced increase in IRS-1/-2 phosphorylation was accompanied by an increase in the association with and activation of PI 3-kinase. PRL-induced IRS-2 phosphorylation and its association with PI 3-kinase did not add to the effect of insulin. PRL also induced JAK2, SHC, ERK1 and ERK2 phosphorylation in neonatal islets, demonstrating that PRL can activate MAPK. These data indicate that PRL can stimulate the IRSs/PI 3-kinase and SHC/ERK pathways in islets from neonatal rats.

Key words

Prolactin - Insulin - Neonatal Rat Islets - Insulin Receptors Substrates 1/2 - PI 3-Kinase - MAP-Kinase - Wortmannin

Full Text

References

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Prof. A. C. Boschero

Departamento de Fisiologia e Biofísica · Instituto de Biologia · CP 6109 · Universidade Estadual de Campinas (UNICAMP)

Campinas 13083-970 · SP · Brasil

Phone: 55 19 3788 6202

Fax: 55 19 3289 3124

Email: boschero@unicamp.br