Effects of circulating norepinephrine on platelet, leukocyte and red blood cell counts by alpha₁-adrenergic stimulation

In the past, norepinephrine (NE) has generally been considered to serve more as a neurotransmitter than as a a hormone.¹ This notion has been based largely on studies of intermediary metabolism and glucose counterregulation. However, from the point of view of the cardiovascular system, the potential humoral role of NE may have been underestimated. We² and others³ have demonstrated that circulating NE is important in regulating renal renin release. We have also found a consistent increase in hematocrit during NE infusion,² and have reasoned that if circulating NE is a true "stress hormone," then stress-related increases in platelet and leukocyte counts could also be NE-dependent. The obvious implications for cardiovascular morbidity and mortality prompted these preliminary studies to investigate hormonal effects of NE on blood elements.