Microspectrophotometry of mitochondrial cytochrome P-450 in single adrenal cells

The cytochrome P-450 is known to be a key enzymic component in steroid hydroxylation. Biochemically it is localized in adrenal cells, both in the mitochondrial and in the microsomal fractions. Owing to its characteristic light absorptivity, attempts were made at its localization and measurement in a microspectrophotometric system. Specific difference spectra were obtained in the cytoplasm of some cells from an adrenal cell suspension before and after saturation with carbon monoxide. Scanning at 450 nm showed slender absorption maxima after CO saturation randomly distributed in the cytoplasm. These may be attributed to mitochondria or larger cytoplasmic functional units including mitochondria.