CYTOSKELETAL CONTROL OF THE APICAL SURFACE TRANSFORMATION OF RAT UTERINE EPITHELIUM

During early pregnancy, in the lead up to blastocyst implantation, the apical cell surface of luminal epithelial cells of the rat uterus und ergo a dramatic shape transformation. This study aims to investigate t he role of the cytoskeleton in this apical transformation by consideri ng the effects of the drugs cytochalasin D and colchicine on the uteri ne luminal cell surface. The results are determined using transmission and scanning electron microscopy. In vivo exposure to cytochalasin D during oestrus, as well as on day 1 of pregnancy, did not affect the l ong, regular surface microvilli. This drug, however, did disrupt the t erminal web within the apical cytoplasm of these cells. Disruption of microfilament (MF) polymerization by cytochalasin D on day 4 of pregna ncy induced a cell surface transformation, resulting in the appearance of numerous irregular projections normally present during blastocyst implantation on day 6 of pregnancy. Colchicine did not alter the uteri ne microvilli of oestrus or day 1 pregnant tissue. Unlike the effect o f cytochalasin D, colchicine-induced microtubule (MT) disruption on da y 4 of pregnancy did not increase irregular projections and hence this treatment did not result in the cell surface appearance associated wi th blastocyst implantation. These results indicate that the disruption of MF, rather than MT, contributes to the transformation of the uteri ne luminal cell surface during the lead up to blastocyst attachment.