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Pancreatic β-cell function is essential for the regulation of glucose homeostasis and its impairment leads to diabetes mellitus. Besides glucose, the major nutrient factor, inputs from neural and humoral components and intraislet cell–cell communication act together to guarantee an appropriate pancreatic β-cell function. Data obtained over the last 5 years in several laboratories have revitalized a controversial concept, namely the autocrine feedback action of secreted insulin on β-cell function. While, historically, insulin was suggested to exert a negative effect on β-cells, recent data provide evidence for a positive role of insulin in transcription, translation, ion flux, insulin secretion and β-cell survival. [Copyright &y& Elsevier]

Abstract: Dopamine is a major regulator of sodium reabsorption in proximal tubule epithelia. It induces the endocytosis of plasma membrane Na,K-ATPase molecules, and this results in a reduced capacity of the cells to transport sodium. Dopamine induces the phosphorylation of Ser-18 in the α1-subunit of Na,K-ATPase. Fluorescence resonance energy transfer analysis of cells expressing YFP-α1 and β1-CFP reveals that treatment of the cells with dopamine increases energy transfer between CFP and YFP. This is consistent with a protein conformational change that results in the N-terminal end of α1 moving closer to the internal face of the plasma membrane. [Copyright &y& Elsevier]