Glucagon does not affect catecholamine release in primary cultures of bovine adrenal chromaffin cells.
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.


METHODS
Adrenomedullary cells were cultured in 24-well plates (10(6) 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.
Sharabi
Y
Y
Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1620, USA. sharabiy@ninds.nih.gov
Zimlichman
R
R
Alesci
S
S
Huynh
T
T
Mansouri
R
R
Chun
J
J
Perera
S
S
Pacak
K
K
Goldstein
D S
DS
D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002469:Cell Separation; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D004837:Epinephrine / Q000378:metabolism; D005934:Glucagon / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D018027:Receptors, Glucagon / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D002395:Catecholamines; D012333:RNA, Messenger; D018027:Receptors, Glucagon; D005934:Glucagon; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine