Carbonic anhydrases in the human adrenal gland and its disorders: Immunohistochemical and biochemical studies of the enzymes

To study the possible roles of carbonic anhydrases (CA) in the human adrenal glands, an immunohistochemical study (using polycloncal antibodies against CA I and II), and a biochemical assay of CA activity (based on the change in pH caused by the hydration of CO₂) were performed in normal human adrenal tissue and adrenocortical adenomas. All of 10 normal adrenal glands showed positive staining for CA II in the zona glomerulosa, whereas weak CA I-positive staining was detected in only 5 glands. A biochemical study of 3 normal human adrenal specimens also demonstrated CA activity only in the outer adrenal cortex. Of 26 adrenocortical adenoma specimens ( 15 aldosteronomas, 6 nonfunctioning adenomas, and 5 Cushing’s adenomas), CA I and II immunoreactivity was observed in only 3 and 5 aldosteronoma samples, respectively. A biochemical analysis of CA in 5 adenoma specimens (3 aldosteronomas, 2 nonfunctioning adenomas) detected enzymatic activity in 2 aldosteronomas. In all 26 specimens of non-neoplastic attached adrenals of adrenocortical adenomas, CA II immunoreactivity was present in the zona glomerulosa cells. These results indicate that CAs are present in the zona glomerulosa cells of the non-neoplastic human adrenals glands (but not in the majority of adrenocortical adenomas) and that CA II may constitute the major form of the enzyme. Exclusive localization of CA II in the zona glomerulosa cells in human adrenal glands may suggest a possible involvement of CAs in aldosterone biosynthesis or secretion through ion transport, or both. Our data also suggest that CA II can be used as an immunochemical marker for the zona glomerulosa cells in human adrenal glands.