Regulation of surface topography of mouse peritoneal cells. Formation of microvilli and vesiculated pits on omental mesothelial cells by serum and other proteins.

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Abstract
The mesothelial cells of the mouse omentum provide an in vivo model for the study of the mobilization of labile microvilli on the cell surface. These mesothelial cells are sparsely covered with microvilli and large pits 150-400 nm in diameter, termed vesiculated pits. On the unstimulated cell, the microvilli average 44/100 .mu.m2 and pits, 30/100 .mu.m2 of surface and are rapidly induced to increase in number by the i.p. injection of isologous mouse serum. After 2 min, microvilli increase 3-fold, continue to 7-fold at 30 min, and decrease to 4-fold at 90 min. Vesiculated pits increase with similar kinetics. Bovine serum albumin and .gamma.-globulin also stimulate the microvilli and pits to form, but the response is a slow, gradual rise 5- or 6-fold the normal value at 90 min. Multiple factors, possibly including insulin and immunoglobulins, are involved in the serum effect. The close physical and temporal relationship between microvilli and pits suggests their mobilization by the cell is synchronous and that microvilli aid in regulating the cortical microfilament network in effecting this mobilization.