CALCIUM-DEPENDENT PROTEIN-KINASE-C ACTIVITY IN HUMAN ADRENOCORTICAL NEOPLASMS, HYPERPLASTIC ADRENALS, AND NORMAL ADRENOCORTICAL TISSUE

The calcium- and phospholipid-dependent protein kinase-C (PKC) is a cr itical enzyme of cellular signal transduction. In this report we studi ed calcium-dependent total PKC activity in eight adrenocortical carcin omas (group 1), nine adrenocortical adenomas (group 2), six hyperplasi as (group 3), and five human normal adrenal tissues (group 4). The PKC activity assay was based on phosphorylation of a specific synthetic p eptide from myelin basic protein. The specificity of the assay was con firmed by using an inhibitor peptide common to alpha-, beta-, and gamm a-isoenzymes of PKC. The median value in group 1 was 1.15 pmol P-32/mi n.mu g protein (range, 0.55-2.19), that in group 2 was 1.2 (range, 0.7 4-2.7), that in group 3 was 0.985 (range, 0.6-1.7), and that in group 4 was 1.22 (range, 0.6-3.95). The calcium-dependent total PKC activity was similar in the four groups studied. We did not find any correlati on between urinary total cortisol, serum cortisol, testostesone, dehyd roepiandrosterone, dehydroepiandrosterone sulfate, androstenedione, al dosterone, and estradiol concentrations and PKC activity. These findin gs suggest that the calcium-dependent PKC activity is not elevated in adrenocortical tumors and is not a useful marker of adrenocortical mal ignancy.