Secretion and degradation of glucagon by HIT cells

Diem, P; Walseth, TF; Zhang, HJ; Robertson, RP (1990). Secretion and degradation of glucagon by HIT cells. Endocrinology, 127(4), pp. 1609-12. Chevy Chase, Md.: Endocrine Society 10.1210/endo-127-4-1609

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HIT cells have been widely used to study synthesis and secretion of insulin. It has been assumed that this cell line secretes no other islet hormones. To ascertain whether HIT cells synthesize, secrete, and degrade glucagon, we examined cell extracts for this peptide and compared secretion and degradation of glucagon and insulin during stimulation of the cells by arginine. Glucagon levels in acid extracts of HIT cells were found to be 0.72 +/- 0.15 pmol/mg protein. Both glucagon and insulin were maximally stimulated in a glucagon/insulin molar ratio of 0.029 by arginine concentrations of 25-50 nM, and the concentration of arginine that provided half-maximum responses for both hormones was approximately 3 mM. Diminution of arginine-induced glucagon secretion was caused by somatostatin, a physiological inhibitor of pancreatic islet alpha-cell function. HPLC was used to authenticate the glucagon levels stimulated by arginine for 60 min and measured by RIA. Thirty-six percent of immunoreactive glucagon was found in the fractions representing authentic glucagon, whereas the remaining 64% eluted earlier. Experiments examining the fate of radiolabeled glucagon exposed to HIT cells revealed time-dependent degradation of the radioisotope to earlier eluting forms, which accounted for approximately 50% of the radioactivity by 60 min and was complete by 18 h, indicating that the early peak detected by RIA represented a metabolite of glucagon. Radioisotopic insulin was degraded more slowly with an apparent half-life of approximately 36 h. We conclude that HIT cells are not only able to synthesize, secrete, and degrade insulin, but also much smaller amounts of glucagon.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Gynaecology, Paediatrics and Endocrinology (DFKE) > Clinic of Endocrinology, Diabetology and Clinical Nutrition
UniBE Contributor:	Diem, Peter
ISSN:	0013-7227
ISBN:	1976091
Publisher:	Endocrine Society
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:56
Last Modified:	05 Dec 2022 14:17
Publisher DOI:	10.1210/endo-127-4-1609
PubMed ID:	1976091
Web of Science ID:	A1990EA64200009
URI:	https://boris.unibe.ch/id/eprint/23884 (FactScience: 44912)