Effects of calcitriol on proliferation and differentiation of human fetal jejunum.

Several lines of evidence suggest a role for calcitriol in the regulatory mechanisms of intestinal development. Using organ culture as a model, we have verified whether this hormone influenced the cellular proliferation and differentiation processes of the developing human jejunum. We show that calcitriol supports a proliferative process in the fetal human jejunum at 11 weeks of gestation and a differentiating activity in samples obtained between 16 and 20 weeks. The present data therefore suggest that calcitriol has a biphasic effect on the development of the human intestinal epithelium and warrants caution in extrapolating to human, data observed in developing rodents and human carcinoma cell lines.