Increases in Plasma Digitalis-Like Factor Activity during Insulin-Induced Hypoglycemia

Abstract

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 < 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 < 0.05; water: 18 ± 11 to 49 ± 15 digoxin Eq/ml, p < 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 < 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 < 0.01) after they received insulin. These results suggest that DLF may be involved in the acute stress response to insulin-induced hypoglycemia, and this response may be augmented by salt or fluid loading.

Is Carbohydrate Metabolism Altered among Women Who Have Undergone a Preeclamptic Pregnancy?

“…Sodium excretion is known to be impaired in preeclampsia, documented by studies of the renal excretory ability after acute saline infusion [19]. Finally, a modified cation flux resulting from insulinmediated inhibition of the ATPase-dependent Na + /K + pump leading to accumulation of intracellular Na + , thereby sensitizing the vasculature to pressor agents, cannot be excluded [20]. In fact, an enhanced ability of serum from preeclamptic patients to inhibit Na + /K + ATPase has been observed [21].…”