Abstract
Objective: Human pheochromocytoma tumor cells express glucagon receptors, and bolus i. v. glucagon
injection rapidly increases plasma epinephrine levels, suggesting that glucagon can
directly stimulate adrenomedullary secretion. In this study, we tested whether the
catecholamine secretory response to glucagon was present in bovine chromaffin cells
or exclusive to the tumor cells. Design and Methods: Adrenomedullary cells were cultured in 24-well plates (106 cells per well). After 48 - 72 hours, wells were incubated for 1 - 20 minutes with
(1) incubation medium (control), (2) catecholamine secretagogues (nicotine or potassium
ion), or (3) glucagon (10 - 8 to 10 - 5 M). After incubation, catecholamine contents in medium and cells were assayed by
high-pressure liquid chromatography with electrochemical detection. Fractional release
rates of epinephrine, norepinephrine, and dopamine were calculated and compared to
controls. Reverse-transcriptase PCR was performed to compare expression of mRNA of
the glucagon receptor in chromaffin cells and pheochromocytoma cells. Results: Nicotine and potassium evoked time-dependent release of epinephrine, norepinephrine,
and dopamine. Glucagon did not affect catecholamine secretion at any concentration.
Reverse-transcriptase PCR failed to detect mRNA for glucagon receptor in bovine adrenomedullary
cells, but did detect it in human pheochromocytoma cells. Conclusions: In contrast to pheochromocytoma tumor cells, bovine adrenomedullary chromaffin cells
do not express the glucagon receptor, and therefore do not secrete catecholamines
in response to glucagon.
Key words
Adrenal medulla - Glucagon - Catecholamines - Chromaffin cell - Pheochromocytoma
References
2+ influx, intracellular Ca2+ levels and secretion of catecholamines in cultured adrenal chromaffin cells.
Neurochem Int.
1996;
28
325-334
sharabiy@ninds.nih.gov
