On Day 6-7 during the postimplantation period, CRABP(II) was expressed in the decidual cells in the implantation chamber. CRBP was also found in the same area. Preliminary data in this laboratory have shown that both human and rat uterine stromal cells that are induced to de-cidualize in vitro gain the ability to produce retinoic acid from retinol (unpublished results). Recently it was reported that decidual cells have both RARs and RXRs. This suggests that retinoic acid, locally generated from retinol, could be involved in the differentiation of stromal cells to decidual cells and/or that it may function in the process of implantation and/or early embryo development. Previous work has demonstrated that retinol-deficient pregnant rats frequently resorbed embryos and that this was accompanied by obvious placental lesions. ventolin inhaler

It is believed that CRABP is involved in control of the level of retinoic acid available to its nuclear receptors, via sequestration and increased catabolism. The expression of CRABP in the smooth muscle cells and temporal expression in the stromal cells on Day 1 may then be explained by CRABP’s serving a role as a protector of these cells at that time from the effects of retinoic acid produced by the epithelium.