Hypertension, Vol 1, 572-582, Copyright © 1979 by American Heart Association
SM Friedman
Transmembrane Na+ and K+ gradients in the rat tail artery were dissipated
by overnight incubation in K-free PSS at 10 degrees C and then allowed to
recover in normal physiologic salt solution (PSS) at 37 degrees C. The
active extrusion of Na+ and uptake of K+ during the recovery period was
monitored with Na+ and K+ selective glass electrodes. Passive exchanges
were differentiated by re-admitting K+ at 3 degrees C, or in the presence
of 1 mM ouabain at both 3 degrees C and 37 degrees C. Active exchange was
switched on by an abrupt transfer of the tissue from 3 degrees C to 37
degrees C. Active exchange, measured in perfused, superfused, or
sequentially incubated arteries, was distinctly enhanced in young (16-, 20-
and 26-week-old) spontaneously hypertensive rats (SHR) of the Okamoto
strain compared with age-matched Wistar-Kyoto normotensive (WKY) controls.
No such difference was observed in rats with hypertension of 7 or 12 weeks'
duration and equal severity induced by unilateral constriction of the renal
artery. Steady- state Nai and Ki were measured after washing the tissues
for 45 minutes at 3 degrees C in lithium-substituted medium to exchange
extracellular sodium with lithium. Cell sodium in these tissues was further
partitioned into a free component proportional to [Na]0 and an independent,
constrained component. Cell potassium was found to be distinctly elevated
in 2- and 4-month-old SHR, while free cell sodium remained normal, despite
increased cell permeability demonstrable in a significant exchange of
lithium for cell potassium and sodium even at 3 degrees C.
ARTICLES
Evidence for enhanced sodium transport in the tail artery of the spontaneously hypertensive rat
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