Abstract-Cardiac sympathetic stimulation activates ␤-adrenergic (␤-AR) receptors and protein kinase A (PKA) phosphorylation of proteins involved in myocyte Ca regulation. The Na/K-ATPase (NKA) is essential in regulating intracellular [Na] ([Na] i ), which in turn affects [Ca] i via Na/Ca exchange. However, how PKA modifies NKA function is unknown. Phospholemman (PLM), a member of the FXYD family of proteins that interact with NKA in various tissues, is a major PKA substrate in heart. Here we tested the hypothesis that PLM phosphorylation is responsible for the PKA effects on cardiac NKA function using wild-type (WT) and PLM knockout (PLM-KO) mice. We measured NKA-mediated [Na] i decline and current (I Pump ) to assess ␤-AR effects on NKA function in isolated myocytes. In WT myocytes, 1 mol/L isoproterenol (ISO) increased PLM phosphorylation and stimulated NKA activity mainly by increasing its affinity for internal Na (K m decreased from 18.8Ϯ1.4 to 13.6Ϯ1.5 mmol/L), with no significant effect on the maximum pump rate. This led to a significant decrease in resting [Na] i (from 12.5Ϯ1.8 to 10.5Ϯ1.4 mmol/L). In PLM-KO mice under control conditions K m (14.2Ϯ1.5 mmol/L) was lower than in WT, but comparable to that for WT in the presence of ISO. Furthermore, ISO had no significant effect on NKA function in PLM-KO mice. ATPase activity in sarcolemmal vesicles also showed a lower K m (Na) in PLM-KO versus WT (12.9Ϯ0.9 versus 16.2Ϯ1.5). Thus, PLM inhibits NKA activity by decreasing its [Na] i affinity, and this inhibitory effect is relieved by PKA activation. We conclude that PLM modulates the NKA function in a manner similar to the way phospholamban affects the related SR Ca-ATPase (inhibition of transport substrate affinity, that is relieved by phosphorylation). Key Words: Na pump Ⅲ phospholemman Ⅲ signal transduction Ⅲ ion channels A ctivation of the sympathetic nervous system and cardiac ␤-adrenergic (␤-AR) receptors causes cAMP formation and activation of protein kinase A (PKA). In cardiac myocytes, PKA phosphorylates several targets with key roles in the control of excitation-contraction coupling (ECC), including L-type Ca 2ϩ channels, phospholamban (PLB) and troponin-I, as well as other sarcolemmal proteins such as voltage-gated Na and K channels and phospholemman (PLM).During sympathetic activation, the larger Ca influx via more frequent and larger Ca current must be balanced by enhanced Ca extrusion via the Na/Ca exchange (NCX) that is driven by larger Ca transients. This increases Na influx at each beat, along with more frequent and larger Na current, which increases intracellular [Na] ([Na] i ). To limit the rise in [Na] i , the greater Na influx must be compensated for by an enhanced Na extrusion via the Na/K pump (NKA). Indeed, many early studies indicated stimulation of the Na-pump by ␤-AR activation. 1-3 However, there is controversy at present because some recent studies in single myocytes using NKA pump current (I Pump ) found either stimulation, 4 -6 inhibition, 7,8 or no change 9 in I Pump on ␤-...

Remote ischemic preconditioning (IPC) reduces tissue injury caused by ischemia-reperfusion (IR) in distant organs. We tested the hypothesis that remote IPC (rIPC) modifies inflammatory gene transcription in humans. Using a microarray method, we demonstrated that a simple model of brief forearm ischemia suppresses proinflammatory gene expression in circulating leukocytes. Genes encoding key proteins involved in cytokine synthesis, leukocyte chemotaxis, adhesion and migration, exocytosis, innate immunity signaling pathways, and apoptosis were all suppressed within 15 min (early phase IPC) and more so after 24 h (second window IPC). Changes in leukocyte CD11b expression measured by flow cytometry mirrored this pattern, with there being a significant (P = 0.01) reduction at 24 h. The results of this study show that the rIPC stimulus modifies leukocyte inflammatory gene expression. This effect may contribute to the protective effect of IPC against IR injury and may have broader implications in other inflammatory processes. This is the first study of human gene expression following rIPC stimulus. rIPC stimulus suppressed proinflammatory gene transcription in human leukocytes.