Increases in plasma digitalis-like factor activity during insulin-induced hypoglycemia

Digitalis-like factor (DLF) appears to be widely distributed throughout the body, and has been specifically localized to the mammalian hypothalamus. In this study we monitored the DLF response to insulin-induced hypoglycemia in 11 normal males. Hypoglycemia was associated with a significant increase in serum DLF activity over basal values (40 +/- 5 pg digoxin Eq/ml, mean +/- SEM) at 60 min (83 +/- 8 pg digoxin Eq/ml) and 90 min (86 +/- 10 pg digoxin Eq/ml) following insulin administration (p less than 0.01). We measured the DLF response to insulin-induced hypoglycemia in other men after infusion of hypertonic saline (n = 8) or after oral water-loading (n = 8). Saline infusion (0.06 ml 5% saline/kg BW/min for 120 min prior to insulin infusion) or water loading (20 ml/kg BW over 60 min completed 30 min before insulin infusion) alone significantly increased serum DLF (saline: 21 +/- 5 to 60 +/- 18 pg digoxin Eq/ml, p less than 0.05; water: 18 +/- 11 to 49 +/- 15 digoxin Eq/ml, p less than 0.05). DLF activity was further significantly increased within each group 60 and 90 min after administration of insulin. In the group infused with hypertonic saline, insulin caused increases of serum DLF from 60 +/- 18 at time 0 to 170 +/- 17 pg digoxin Eq/ml at peak (p less than 0.01). Similarly, in the oral water-loaded group serum DLF increased from 49 +/- 15 at time 0 to 127 +/- 24 pg digoxin Eq/ml at peak (p less than 0.01) after they received insulin.2=