Norepinephrine Stimulation of Lymphocyte ATPase by an Alpha Adrenergic Receptor Mechanism

Abstract

The effects of norepinephrine in interaction with adrenergic blocking compounds were studied on membrane adenosine triphosphatase (ATPase) activities of human lymphocytes and lymphoblasts. Sodium-potassium ion exchange pump activity was assayed by ⁸⁶Rb uptake and ATPase activity of membrane fractions was assayed by ADP and inorganic phosphate generation. The results of these studies indicate that norepinephrine acts by an alpha adrenergic mechanism to enhance membrane sodium-potassium ion exhange pump activity and ATPase activity. The pharmacologic and ionic dissection of the adrenergic sensitivity of ATPase activity indicates that this alpha adrenergic mechanism is related to membrane ATPase activities in addition to that associated with the ion exchange pump. Analysis of fractions obtained by sucrose gradients indicates that the action of norepinephrine is localized in the plasma membrane. Beta adrenergic stimulation was observed to inhibit ATPase activity. The complexity of adrenergic effects on membrane ATPase suggests interactions of hormone modulation of membrane nucleotide cyclases and transport-related ATPase enzymes.