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Plasma dopamine-beta-hydroxylase activity in phaeochromocytoma
Clinical Endocrinology
|March 1, 1976
Summary
Plasma dopamine-beta-hydroxylase (DbetaH) activity in phaeochromocytoma patients was similar to healthy subjects, suggesting diffusion, not exocytosis, is the main catecholamine release mechanism. Postoperative changes hint at tumor heterogeneity.
Area of Science:
- Biochemistry
- Endocrinology
- Oncology
Background:
- Plasma dopamine-beta-hydroxylase (DbetaH) activity is a marker for catecholamine secretion via exocytosis.
- Phaeochromocytoma is a tumor of the adrenal medulla that secretes excess catecholamines.
Purpose of the Study:
- To investigate the mechanism of catecholamine release in patients with phaeochromocytoma.
- To compare plasma DbetaH activity in phaeochromocytoma patients with healthy subjects.
Main Methods:
- Preoperative plasma DbetaH activity was measured in eight phaeochromocytoma patients.
- Urinary catecholamine concentrations were also determined.
- Plasma DbetaH activity was reassessed seven days after surgical tumor removal in one patient.
Main Results:
- Mean preoperative plasma DbetaH activity in phaeochromocytoma patients was not significantly different from healthy subjects, despite elevated urinary catecholamines.
- One patient showed a 60% decrease in plasma DbetaH activity seven days after surgery.
Conclusions:
- Catecholamine release from phaeochromocytomas predominantly occurs via diffusion across plasma membranes, not exocytosis.
- Tumor heterogeneity may exist, with exocytosis potentially contributing to catecholamine release in some patients.