Abstract
The effect of various vitamin D_3 analogues on chick embryonic duodenal alkaline phosphatase (AP) was observed using organ culture techniques. 1) AP was maximally induced by 1,25- (OH)_2-D_3,when 20-day old embryonic duodenum was cultured in the presence of 62.5 nM of 1,25- (OH)_2-D_3,1α-OH-⊿^<24>-D_3,1α, 24 [R], 25-(OH)_3-D_3,1α, 24 [S], 25-(OH)_3-D_3,1α, 24 [R]-(OH)_2-D_3,or 1α, 24 [S]-(OH)_2-D_3. 2) In the two different stereoisomers of 24-hydroxylated vitamin D_3,the Risomer showed higher activity on the AP induction than the corresponding S isomer. 3) No effect of vitamin D_3 analogues on sucrase activity was observed. 4) The inhibitory effect of cycloheximide on the induction of AP activity by 1,25- (OH)_2-D_3 was larger than that of actinomycin D.
