Title: Subcellular location of rat liver calciferol-25-hydroxylase
Abstract: The major calciferol-25-hydroxylase from rat liver is shown to be localized in the microsomal cell fraction. As was previously observed in whole homogenates, microsomal calciferol-25-hydroxylase activity decreases dramatically following in vivo vitamin D3 administration. In the absence of added cytoplasmic fraction from liver, vitamin D3 is completely degraded by incubation with liver microsomes and other cell fractions. Addition of liver cytoplasmic fraction to the microsomal incubation both inhibits destruction of vitamin D3 and stimulates production of 25-hydroxyvitamin D3 demonstrating the existence of a liver cytoplasmic factor important to the microsomal 25-hydroxylation of vitamin D3. Isolated mitochondria are able to convert vitamin D3 to compounds similar in polarity to 25-hydroxyvitamin D3. The major product of this reaction is not 25-hydroxyvitamin D3. The mitochondrial reactions are not influenced by in vivo vitamin D3 administration, and their products do not appear when [3H]vitamin D3 is incubated with the liver homogenates from vitamin D3-treated rats, casting doubt on their physiological significance.
Publication Year: 1974
Publication Date: 1974-01-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 194
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