ABSTRACT
Endothelin (ET)-1 induces proliferation of various cells including smooth muscle cells, fibroblasts, glomerular mesangial cells, endothelial cells and osteoblasts. ET-1 also stimulates synthesis of interleukin (IL)-6 in endothelial and bone marrow stromal cells of rat. It is well known that IL-6 modulates megakaryocytopoiesis. Some studies have indicated that megakaryocytes express both ET receptors and they are targets for ET. Therefore we planned to examine the effects of ET-1 on the growth of normal megakaryocytic cells in rat bone marrow primary cell culture. Bone marrow cells were cultured at 37 degrees C, in an incubator atmosphere of 5% CO2 in air and 95% relative humidity for nine days. ET-1 at 10(-7), 10(-8 ) and 10(-11) M, and control with saline were added at the beginning of the experiment protocol. At each day, plasma clots were stained using direct-coloring thiocholin method for acetylcholinesterase activity. Although 10(-7) M ET-1 did not change the proliferation of megakaryocytic cells, this could be due to the presence of over crowded fibroblasts in the same environment. 10(-8) M ET-1 stimulated megakaryocytic cell growth to 234% over the control on the fifth day. ET-1 at a concentration of 10(-11) M also rised the megakaryocytic cell number significantly reaching up to 86% at the sixth day. Our results indicate that ET-1 may modulate the growth of megakaryocytic cells by an autocrine and/or paracrine action.
