EFFECT OF DEXAMETHASONE ON THE FETAL MOUSE SMALL-INTESTINE IN ORGAN-CULTURE

The formation of intestinal villi (organogenesis phase) may be studied in organ culture with a completely synthetic medium in 15-day fetal mouse duodenal explants. However, in these explants absorptive cells remained poorly differentiated with all the hormones studied except with epidermal growth factor. To elucidate the role of hormones and other factors on the maturation of absorptive cells (maturation phase) in the fetal rodent in organ culture, explants were taken after the organogenesis phase. Seventeen-day mouse duodenal explants can be cultured during 48 h with Leibovitz L-15 medium in a 95% O2-5% CO2 atmosphere provided that the explants are relatively large (5 .times. 2 mm). With this method, dexamethasone (Dx) had a direct effect on the maturation of the fetal duodenal mucosa. The addition of Dx (300 ng/ml) to the completely synthetic medium improves the morphology of the explants, induces a significant increase in maltase activity in the tissues and reduces significantly the labeling index of the duodenal explants after 48 h of culture. Direct action of Dx on the duodenal mucosa is shown for the 1st time in organ culture using a completely synthetic medium. This method will permit the study of the effects of other intrinsic and extrinsic factors on the regulation of enzymatic maturation in fetal small intestine.