Stimulation of chick gut alkaline phosphatase activity by actinomycin D and 1,25-dihydroxyvitamin D3: evidence for independent mechanisms.

We observed that inhibitors of RNA synthesis, actinomycin D and cordycepin, stimulate chick duodenal alk Pase activity by means which are additive to the stimulaation by the biologically active metabolite of vitamin D3, 1,12(OH)2D3, and its analogue, 1 alpha OH D3. The protein synthesis inhibitor, cycloheximide, inhibited basal alk Pase activity and blocked its stimulation by actinomycin D and 1,25(OH)2D3. Both actinomycin D and cycloheximide blocked the ability of 1,25(OH)2D3 and 1 alpha OHD3 to raise serum calcium levels. The paradoxical stimulation of duodenal alk Pase activity by RNA synthesis inhibitors additive to the stimulation by 1,25(OH)2D3 suggests that alk Pase activity is controlled by mechanisms other than gene activation. (J LAB CLIN MED 94:88, 1979.)