Extraadrenal Immunohistochemical Distribution of Steroid 21-Hydroxylase in Human

Using an antibody against cytochrome P-450 specific for steroid 21-hydroxylase (P-45O_C21), extraadrenal distribution and localization of the enzyme were immunohistochemically examined on various normal human tissues. Immunoreactive P-450_C21 was demonstrated in the renal tubular system, especially in distal tubules and cortical and medullary collecting tubules : excretory ducts including intercalated ducts of the pancreas and salivary glands ; secretory ducts of the mammary glands. The immunoreactivity for P-450_C21 was not present in the colon and liver. Transepithelial transport of sodium, potassium and hydrogen ions occurs in those sites where P-450_C21 is present and mineralocorticoid receptors are presumed to be present. Relationship of extraadrenal 21-hydroxylase, which produces deoxycorticosterone locally, to a mineralocorticoid action is proposed.