The effect of 1alpha-hydroxyvitamin D3 and cortisone on the development of chick duodenal alkaline phosphatase in organ culture.

The development of alkaline phosphatase influenced by 1 alpha-OH-D3 (a synthetic active form of vitamin D3) and cortisone was studied in chick duodenal organ cultures. The administration of cortisone to the embryo in ovo on the 14th day of incubation resulted in a precocious increase in alkaline phosphatase after six days (20-day embryo). When duodena from 14-, 18- and 20-day embryos were cultured in the presence of cortisone, there was no significant enhancement of alkaline phosphatase activity except for a marginal effect observed in the 18-day duodenum. On the other hand, the alkaline phosphatase activity in cultured duodena from 20-day chick embryos was significantly stimulated by the addition of 1 alpha-OH-D3. The effects of cortisone and 1 alpha-OHD-3 were not additive. The activity of maltase, another intestinal enzyme, was not influenced by 1 alpha-OH-D3. Studies on inactivation of alkaline phosphatase by EDTA suggest that the observed increase in alkaline phosphatase activity induced by the administration of 1 alpha-OH-D in vitro may be related to the qualitative changes in the enzyme that take place during development in vivo.