Faculty Publications

Norepinephrine Stimulation of Sodium Transport in Necturus Urinary Bladder Epithelium

Document Type

Article

Keywords

(Necturus), Membrane voltage, Norepinephrine, Short-circuit current, Sodium ion transport, Urinary bladder

Journal/Book/Conference Title

BBA - Biomembranes

Volume

1022

Issue

1

First Page

79

Last Page

86

Abstract

Norepinephrine alters the transepithelial electrical properties of an open-circulated urinary bladder from the mud puppy, Necturus maculosus. When 10-5 M norepinephrine is superfused over the serosa of the epithelium, the transepithelial voltage (Vt) and short-circuit current (Isc increase s the (Rt decreases. The norepinephrine-mediated changes are reversed by the addition of amiloride (5 · 10-5 M) to the mucosal Ringer's solution. The serosal adrenoceptors mediating the Na+ transport are more sensitive to norepinephrine (EC50 = 1.2 · 10-6 M) than to epinephrine or isoproterenol. Since the Isc is blocked selectively by the antagonist, phenoxybenzamine, stimulation of active transepithelial Na+-flux by catecholamines is mediated by an α-adrenoceptor. The apical cell membrane voltage (Va) and fractional resistance (fRa) were recorded using conventional KCl-filled microelectrodes. Untreated tissues have Va close to 0 mV while the basolateral membrane voltage (Vb) is between -85 and -95 mV. About 90% of Rt is apical cell membrane resistance (fRa). When amiloride inhibits sodium transport, Va becomes negative, Vb hyperpolarizes slightly and fRa increases to 97%. On the other hand, if the bladders are treated with norepinephrine, fRa decreases to 79% as Va becomes positive and Vb depolarizes. When Rt changes, the resistance of the paracellular pathway (Rp) is unaltered. Changes in the electrical properties of the tissue appear to be mediated primarily by alterations in Ra. Since the Necturusbladder does not respond to antidiuretic hormone, this study implies that biogenic amines regulate Na+ transport in the epithelium. © 1990.

Department

Department of Biology

Original Publication Date

2-16-1990

DOI of published version

10.1016/0005-2736(90)90402-A

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