Insulin-Like Growth Factor-2 Regulation of Conceptus Composition: DISCUSSION(7)

It is not known if one or many exchange tissues are involved in regulating the extracellular fluid volume in the mouse conceptus. It is unlikely that the number of cells is a major determinant. There is only a 15% decrease in the DNA content of the placenta + fetus at a time when the cavities are reduced by 25% (Table 1). For a similar reason, it is also unlikely that the cell numbers of the fetal placentas are decisive in regulating these volumes. When there is a minor and nonsignificant reduction in the DNA content of this fraction (Table 5, ICM series), then the volume of the cavities is reduced by 25% (Table 3). We therefore favor an explanation of the effects of IGF-2 deficiency based on its physiological functions. buy cheap antibiotics

IGF-2 might control fluid uptake by a direct action on the maternal capillaries. Currently, only IGF-1 is known to increase fluid movement from the capillaries to the extra-vascular spaces, with increased capillary permeability and increased ‘‘filtration’’ following increased blood flow as the probable mechanisms. It is probable that IGF-2 has a similar effect because both the IGFs are potent inducers of vascular endothelial growth factor (VEGF) mRNA and protein, and VEGF increases capillary permeability as well as promoting angiogenesis. Further, IGF-2 stimulates angiogenesis in both the chorioallantoic membrane and rat cornea assays. The maternal and fetal circulatory systems in the placenta provide extensive surfaces for these local actions.

This entry was posted in Growth Factor and tagged Genotypes, Growth Factor, Inner Cell Mass, Trophectoderm.