This is biologically relevant since endothelium itself has a powerful regulatory effect on the underlying vascular smooth ICI 182780 129453-61-8 muscular cells. Hence, the characterization of the global pattern of transcriptional modifications in the endothelium is important for better understanding the mechanism of action of insulin. The development of microarray technology represents a powerful tool for characterizing such large-scale changes in transcript levels. For example, this methodology was applied to investigate the effects of intensive insulin treatment for 10 days on the mRNA profile in skeletal muscle of type 2 diabetic patients. With a similar methodology, it has been shown that insulin directly modulates the mRNA levels of about 800 genes induced by 3 hours of euglycemic hyperinsulinemic clamp in the vastus lateralis muscle of healthy lean subjects. More recently, it has been shown that insulin is able to regulate different processes within the placenta at different gestational stages, using a global microarray analysis of primary trophoblasts. In pre/post stimulus studies in which the transcriptional response is monitored at one specific time instant after a prolonged insulin exposure, genes showing a transient response followed by a return to the pre-stimulus expression or a systematic, but small in magnitude, change in the expression, are likely to be missed. On the opposite, monitoring the dynamic response using more than one time samples after the stimulus allows detecting these genes as differentially expressed and provides a description of the transcriptional expression patterns of the response. Transient behavior might be characteristic, and, if common to a number of genes associated to the same functional group, might give insight into the function performed by the gene circuitry. The aim of the present work is to exploit the potential of a dynamic study to investigate the dynamic transcriptional response of endothelial cells following insulin stimulation. As far as we know, this has not been previously addressed in the literature for endothelial cells stimulated with insulin. To distinguish between insulin effect and other processes that take place in the cell simultaneously, but are not induced or inhibited by insulin, treated cells were compared with control cells. Experiments were carried out on human umbilical vein endothelial cells. As far as we know, this is the first systematic study in the literature monitoring transcriptional response to insulin in endothelial cells, in a time series microarray experiment. The objective of this study was to utilize DNA microarray technology to assess the transcriptional response to insulin in endothelial cells, in a time series microarray experiment.