IMMUNOFLUORESCENT LOCALIZATION OF 25-HYDROXYVITAMIN-D3-1ALPHA-HYDROXYLASE FERREDOXIN IN THE RENAL TISSUE OF CHICK

The chick renal mitochondrial 25-hydroxyvitamin-D3-1α-hydroxylase is composed of three proteins, namely, cytochrome P-450, iron-sulfur protein (ferredoxin) and flavoprotein. Antibodies were raised in rabbits against homogenous preparations of the ferredoxin. The antibodies were used in indirect immunofluorescence studies to localize the ferredoxin along the nephron of renal tissues obtained either from vitamin D3-deficient or vitamin D3-sufficient chicks. The ferredoxin is predominantly localized in the glomerulus and proximal convoluted tubules. These results suggest that, in addition to the mitochondrial localization of the 1-hydroxylase, the enzyme may also be present in renal nuclei. The amount of the ferredoxin in kidney, as evidenced by the intensity of fluorescence, appeared to be independent of the vitamin D status of the chick. This finding indicates that changes in the concentration of the renal ferredoxin is not a major factor in the regulation of the 1-hydroxylase activity.