Catecholamine metabolism in pheochromocytoma and normal adrenal medullae

The tissue contents of catecholamine, its precursor and its major metabolites were determined in 8 human pheochromocytomas and 26 normal adrenal glands. Pheochromocytomas contained significantly larger amounts of norepinephrine, dopamine, dihydroxyphenylalanine, tyrosine hydroxylase activity, metanephrine, normetanephrine and vanillylmandelic acid than did normal adrenal medullae. The content ratio of epinephrine/norepinephrine in normal adrenal medullae was significantly higher than that in pheochromocytomas but there were considerable individual variations in the metanephrine/normetanephrine and vanillylmandelic acid/3-methoxy-4-hydroxyphenylethylglycol ratios in pheochromocytomas. In normal adrenal medullae the tissue content of tyrosine hydroxylase activity correlated inversely with the tissue contents of epinephrine (r equals -0.78, p less than 0.001), norepinephrine (r equals -0.78, p less than 0.001) and total catecholamines (r equals -0.87, p less than 0.001), respectively but no significant relation was found between both parameters in pheochromocytomas. These results indicate the possible presence of a negative feedback mechanism of catecholamine via tyrosine hydroxylase in normal adrenal medullae but none in pheochromocytomas. In addition, the increased degradation catecholamine pathway in pheochromocytomas appears to be unstable compared to that in normal adrenal medullae.