Responses of cremasteric arterioles of spontaneously hypertensive rats to changes in extracellular K+ concentration.
OBJECTIVE
The goal of this study was to determine the effect of changes in extracellular K+ concentration ([K+]o) on active tone in cremasteric arterioles of spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto (WKY) and Wistar controls.


METHODS
Diameters of third- and fourth-order arterioles were measured in the cremaster muscle of hypertensive and normotensive rats during abrupt changes in superfusate K+ concentration from 4.7 mM to 0 mM to 15 mM K+.


RESULTS
Arterioles constricted in response to superfusion with 0 mM K+ and exhibited a large, transient dilation in response to an abrupt change from 0 mM to 15 mM [K+]o. Arteriolar dilation in response to 15 mM K+ was significantly larger in 12-15-week-old SHR than in WKY or Wistar controls. Arteriolar responses to 15 mM K+ were not significantly different in 4-6-week-old SHR and WKY. Dilator responses to 15 mM K+ were generally inhibited by 1 mM ouabain, although ouabain was less effective in inhibiting 15 mM K(+)-induced dilation in arterioles of SHR and WKY than in Wistar rats.


CONCLUSIONS
Dilation of cremasteric arterioles in response to 15 mM [K+]o is mediated, at least in part, via stimulation of the electrogenic Na+/K+ pump, although Na+/K(+)-pump-independent components may also contribute to the response. Arterioles of SHR with established hypertension exhibit an altered response to elevated [K+]o which is not present in SHR in the early stage of hypertension.
Lombard
J H
JH
Department of Physiology, Medical College of Wisconsin Milwaukee, USA.
Stekiel
W J
WJ
D000818:Animals; D001160:Arterioles / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000098:blood supply*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D014666:Vasomotor System / Q000187:drug effects*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium