The effect of alpha-adrenergic blockade on responses of peripheral blood cells to acute insulin-induced hypoglycaemia in humans.

Acute hypoglycaemia provokes rapid changes in peripheral blood cell counts. To examine possible adrenergic mechanisms modulating these changes, counts of peripheral blood cells including lymphocytes, granulocytes and erythrocytes were measured in response to acute hypoglycaemia in a group of six normal subjects in control conditions (study 1), and during alpha-adrenergic blockade with phentolamine (study 2). In study 1 hypoglycaemia provoked a biphasic leucocyte response, with an early rise in lymphocyte count and a later rise in granulocyte count. The erythrocyte count increased modestly following hypoglycaemia. During alpha-adrenergic blockage, the rise in total leucocyte count was diminished, with the rise in the lymphocyte count being greatly obtunded. These findings suggest that the increments of peripheral lymphocyte and erythrocyte counts in response to acute insulin-induced hypoglycaemia are mediated via alpha-adrenoreceptors.