Suppression of 1,25-dihydroxy-vitamin D 3-dependent calcium transport by protein synthesis inhibitors and changes in phospholipids in skeletal muscle

Abstract

The effects of protein synthesis inhibitors on 1,25-dihydroxy-vitamin D 3-dependent Ca uptake were evaluated in vitamin D-deficient chick soleus muscle and chick embryo myoblast cultures in order to obtain information about the mechanism by which 1,25-dihydroxy-vitamin D 3 affects muscle calcium transport. Puromycin (50 μM, 5 h) and cycloheximide (50 μM, 24 h) blocked the increase in Ca uptake induced by the metabolite in soleus muscle and myoblasts, respectively. Actinomycin D (1.6 μM, 12 h) was also effective in inhibiting 1,25-dihydroxy-vitamin D 3-dependent Ca uptake in myoblasts. These results suggest that the effects of 1,25-dihydroxy-vitamin D 3 on muscle Ca uptake are mediated by de novo protein and RNA synthesis. In addition, it could be observed that myoblasts treated with 1,25-dihydroxy-vitamin D 3 had increased lipid phosphorus, phosphatidylcholine and sphingomyelin contents. These changes may be the consequence of the nuclear action of the sterol or, alternatively, represent an independent effect as has been proposed for intestine.