This Article Free upon publication Full Text Full Text (PDF) All Versions of this Article: 49/6/1351    most recent HYPERTENSIONAHA.107.088732v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sonalker, P. A. Articles by Jackson, E. K. Search for Related Content PubMed PubMed Citation Articles by Sonalker, P. A. Articles by Jackson, E. K. Related Collections Other hypertension Other Treatment

(Hypertension. 2007;49:1351.)
© 2007 American Heart Association, Inc.

Original Articles

Norepinephrine, via ß-Adrenoceptors, Regulates Bumetanide-Sensitive Cotransporter Type 1 Expression in Thick Ascending Limb Cells

From the Departments of Pharmacology and Medicine, Center for Clinical Pharmacology, University of Pittsburgh, School of Medicine, Pa.

Correspondence to Edwin K. Jackson, Center for Clinical Pharmacology, University of Pittsburgh School of Medicine, 100 Technology Dr, Suite 450, Pittsburgh, PA 15219. E-mail edj{at}pitt.edu

The sympathetic nervous system, via norepinephrine, regulates renal sodium transport, and chronic sympathetic activation causes sustained increases in blood pressure by reducing sodium excretion. Our previous studies show that chronic norepinephrine infusion increases the abundance of the bumetanide-sensitive cotransporter type 1, the apical sodium transporter of the thick ascending limb of Henle’s loop. The present study was initiated to elucidate the mechanisms by which norepinephrine regulates the protein levels of this transporter in an immortalized thick ascending limb epithelial cell line. Treatment with norepinephrine, either alone or in the presence of actinomycin D or cycloheximide, had no effect on cotransporter mRNA levels. Treatment with norepinephrine, however, increased bumetanide-sensitive cotransporter type 1 protein levels (70% increase versus control; P=0.012), and pretreatment with cycloheximide blocked the effect of norepinephrine on bumetanide-sensitive cotransporter type 1 protein levels. To further elucidate the mechanism, thick ascending limb cells were treated with norepinephrine in the presence of phentolamine (-adrenoceptor blocker), propranolol (ß-adrenoceptor blocker), SQ22536 (adenylyl cyclase inhibitor), PD098059 (mitogen-activated protein kinase pathway inhibitor), H-89 (protein kinase A inhibitor), or staurosporine (protein kinase C inhibitor). Treatment with propranolol, SQ22536, and H-89 abolished the effects of norepinephrine on bumetanide-sensitive cotransporter type 1 protein levels, whereas staurosporine had no effect. Treatment with PD098059 partially inhibited the effects of norepinephrine (40% decrease versus norepinephrine; P=0.03), and treatment with phentolamine potentiated the effects of norepinephrine (30% increase versus norepinephrine; P=0.02) on bumetanide-sensitive cotransporter type 1 protein levels. We conclude that regulation of bumetanide-sensitive cotransporter type 1 by norepinephrine proceeds via the ß-adrenoceptor receptor–cAMP–protein kinase A pathway that involves in part mitogen-activated protein kinases and that -adrenoceptor activation negatively regulates bumetanide-sensitive cotransporter type 1 protein levels.

Key Words: BSC-1/NKCC2 • thick ascending limb • norepinephrine • -adrenoceptor • ß-adrenoceptor • cAMP • protein kinase A • cAMP