A fall in portal vein insulin does not cause the alpha-cell response to mild, non-insulin-induced hypoglycemia in conscious dogs.
The aim of the present study was to determine whether a decrease in the portal vein insulin level during non-insulin-induced hypoglycemia is sensed and is responsible for the normal increase in glucagon release from the alpha cell. To address this aim, a glycogen phosphorylase inhibitor was used to create mild, non-insulin-induced hypoglycemia in 2 groups of 18-hour fasted conscious dogs. Arterial insulin was clamped at a basal level in both groups, but in one group (PE) the portal vein insulin level was permitted to fall by approximately 65% while in the other group (POR) it was clamped at a basal level. In both groups glucose was infused at a variable rate to clamp the plasma glucose level at approximately 70 mg/dL. Plasma glucagon (pg/mL) rose to indistinguishable maxima in both groups (56 +/- 3 in PE and 67 +/- 9 in POR). Likewise, glucagon secretion (pg/kg/min) increased similarly (189 +/- 32 to 455 +/- 203 in PE and 192 +/- 50 to 686 +/- 237 in POR). Thus, the increase in glucagon release was not inhibited when the portal vein insulin level was prevented from decreasing (POR group). Clearly, a fall in the portal vein insulin level is not required for a normal alpha-cell response to mild, non-insulin-induced hypoglycemia.
Gustavson
Stephanie M
SM
Department of Molecular Physiology, Diabetes Research and Training Center, Vanderbilt University Medical Center, Nashville, TN 37232-6303, USA.
Nishizawa
Makoto
M
Farmer
Ben
B
Neal
Doss
D
Brissova
Marcela
M
Powers
Alvin C
AC
Cherrington
Alan D
AD
D000818:Animals; D015374:Biosensing Techniques; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood; D004285:Dogs; D005260:Female; D005934:Glucagon / Q000097:blood / Q000378:metabolism; D024981:Glycogen Phosphorylase / Q000378:metabolism; D007003:Hypoglycemia / Q000378:metabolism*; D007328:Insulin / Q000097:blood*; D007515:Islets of Langerhans / Q000502:physiology*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011169:Portal Vein / Q000378:metabolism*
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D005934:Glucagon; D024981:Glycogen Phosphorylase; D009638:Norepinephrine