1. ¹Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical School, Hull HU6 7RX, UK
2. ²Department of Obstetrics and Gynecology, Hull Women and Children's Hospital, Hull HU3 2JZ, UK

Correspondence: Dr SL Atkin, The Michael White Diabetes Centre, 220-236, Anlaby Road, Hull HU3 2RW, UK. E-mail: S.L.Atkin@hull.ac.uk

Received 27 May 2004; Revised 24 January 2005; Accepted 8 February 2005; Published online 5 April 2005.

Abstract

Angiogenesis is characterised by activation, migration and proliferation of endothelial cells and is central to the pathology of cancer, cardiovascular disease and chronic inflammation. Somatostatin is an inhibitory polypeptide that acts through five receptors (sst 1, 2, 3, 4, 5). Sst has previously been reported in endothelium, but their role remains obscure. Here, we report the expression of sst in human umbilical vein endothelial cells (HUVECs) in vitro, during proliferation and quiescence. A protocol for culturing proliferating and quiescent HUVECs was established, and verified by analysing cell cycle distribution in propidium-iodide-stained samples using flow cytometry. Sst mRNA was then quantified in nine proliferating and quiescent HUVEC lines using quantitative reverse transcriptase–polymerase chain reaction. Sst 2 and 5 were preferentially expressed in proliferating HUVECs. All samples were negative for sst 4. Sst 1 and 3 expression and cell cycle progression were unrelated. Immunostaining for sst 2 and 5 showed positivity in proliferating but not quiescent cells, confirming sst 2 and 5 protein expression. Inhibition of proliferating cells with somatostatin analogues Octreotide and SOM230, which have sst 5 activity, was found (Octreotide 10^-10–10^-6 M: 48.5–70.2% inhibition; SOM230 10^-9–10^-6 M: 44.9–65.4% inhibition) in a dose-dependent manner, suggesting that sst 5 may have functional activity in proliferation. Dynamic changes in sst 2 and 5 expression during the cell cycle and the inhibition of proliferation with specific analogues suggest that these receptors may have a role in angiogenesis.