Morphological and functional characterization of beta TC-6 cells--an insulin-secreting cell line derived from transgenic mice.
Morphological analysis of hormone content and functional assessment of hormone secretion were conducted in beta TC-6 cells, an insulin-secreting cell line derived from transgenic mice expressing the large T-antigen of simian virus 40 (SV40) in pancreatic beta-cells. We observed by immunohistochemistry and confocal microscopy that beta TC-6 cells contain abundant insulin and small amounts of glucagon and somatostatin (SRIF). Glucagon usually co-localized with insulin, whereas cells containing SRIF did not contain insulin or glucagon. Static incubation and perifusion experiments demonstrated that beta TC-6 cells at passage 30-45 secrete insulin in response to glucose. In static incubations, maximal stimulation was achieved for glucose concentrations > 2.8 mmol/l glucose, and the half-maximal effect was observed at 0.5 mmol/l. Maximal stimulation was four times greater than HIT-T15 cells at passage 72-81, although HIT cells had a greater response over their basal levels. The magnitude of the insulin response to glucose in perifusion was 1,734 +/- 384 pmol.l-1. min and was 4.6-fold greater in the presence of 3-isobutyl-1-methylxanthine. Low amounts of glucagon were released in response to amino acids. Epinephrine (EPI), and to a lesser extent SRIF, inhibited phasic glucose-induced insulin secretion. A major portion of these inhibitory effects was mediated by pertussis toxin-sensitive substrates. Immunoblots detected the presence of the G-proteins Gi alpha 2, Gi alpha 3, and Go alpha 2. These results indicate that beta TC-6 cells are a glucose-responsive cell line in which insulin exocytosis is physiologically regulated by EPI and SRIF through Gi/Go-mediated mechanisms.
Poitout
V
V
Department of Medicine, University of Minnesota Medical School, Minneapolis.
Stout
L E
LE
Armstrong
M B
MB
Walseth
T F
TF
Sorenson
R L
RL
Robertson
R P
RP
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000096:biosynthesis; D002460:Cell Line; D004837:Epinephrine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D005934:Glucagon / Q000032:analysis* / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis* / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009243:NAD / Q000378:metabolism; D010477:Perfusion; D037342:Pertussis Toxin; D011863:Radioimmunoassay; D013539:Simian virus 40 / Q000235:genetics; D013004:Somatostatin / Q000032:analysis* / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000952:Antigens, Polyomavirus Transforming; D007328:Insulin; D010566:Virulence Factors, Bordetella; D009243:NAD; D013004:Somatostatin; D005934:Glucagon; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D005947:Glucose; D015056:1-Methyl-3-isobutylxanthine; D004837:Epinephrine