The effect of epidermal growth factor (EGF) on the differentiation of the rough endoplasmic reticulum in fetal mouse small intestine in organ culture.

The differentiation of the rough endoplasmic reticulum (RER) of mouse duodenal absorptive cells located at the tip of the villi at 17 days of gestation was compared to that of absorptive cells in duodenal explants of 15-day-old mouse fetuses cultured for 72 hr 1) with Trowell T8 medium (without insulin) alone or supplemented 2) with epidermal growth factor (EGF; 100 ng/ml) or 3) with 25% bovine amniotic fluid (BAF). Glucose-6-phosphatase activity (G6Pase) was localized cytochemically to ensure a better identification of the RER. The intersections of a double lattice falling over and outside the RER were counted and the percentage of intersections over the RER was estimated. With this method, the extent of the RER is not statistically different when the absorptive cells in utero are compared to those of explants cultured with EGF. However, the extent of the RER in the absorptive cells cultured with Trowell T8 medium alone or supplemented with BAF is 50% lower than in the former two groups. It is concluded that EGF promotes the maturation of duodenal absorptive cells in organ culture.