Glucagon Diabetes mellitus Islet microcirculation

α-cells
Zinc
opened K ATP channels
inhibited glucose and pyruvate-stimulated
glucagon secretion
did not inhibit arginine-induced glucagon release
… when K ATP channel activity is bypassed, Zn is unable to
block hormone secretion
Pancreatic ß-cell K + -ATP sensitive channel: SUR1/Kir6.2
SUR1
Kir6.2
Transcripts encoding K ATP subunits were more
abundant in α- than ß-cells (FACS-isolated)
Zinc action probably results from direct activation of
α-cell K ATP channels rather than inhibition of
Ca 2+ channels
37
Site of Zn action may be located on the SUR1 subunit
38
Relative abundance of insulin receptor and GLP-1
receptor transcripts in FACS-isolated α- and ß-cells
and compared with liver
Data are presented relative to ß-cells , n =3, *P < 0.05, **P < 0.01
39 40
Analysis of islet hormone secretion
Analysis of islet hormone secretion
absence
Insulin antiserum
presence
absence
presence
“Zn-free”
exogenous insulin
absence
presence
exogenous insulin
mean ± SE **P < 0.01
41
means+SE **P < 0.01
42