New insight into abnormal muscle vasodilatory responses in aged hypertensive rats by in vivo nuclear magnetic resonance imaging of perfusion.
OBJECTIVE
Increased peripheral arterial resistances and decreased maximum vasodilation are characteristic features of chronic hypertension. However, little data are available in the literature regarding the possible alterations in the temporal patterns of vasodilatory responses elicited by various stimuli.


METHODS
This question was addressed by measuring skeletal muscle perfusion using nuclear magnetic resonance imaging combined with arterial spin labeling.


METHODS
Ninety-week-old male spontaneously hypertensive (SHR; n = 7) and normotensive Wistar Kyoto (WKY; n = 8) rats were studied, and calf muscle perfusion was measured at rest and during reactive hyperemia following total ischemia of 5 and 30 min duration.


RESULTS
Reactive hyperemia profiles differed according to duration of ischemia. In WKY rats, 5 min of ischemia induced a short peak of hyperemia lasting no more than 63 s, while 30 min of ischemia were followed by a prolonged hyperemic response of 261 s. In SHRs, after 5 min of ischemia, peak muscle arterial conductance was decreased to 0.5 +/- 0.3 versus 0.9 +/- 0.3 ml.min(-1).100 g(-1).mm Hg(-1) in the WKY rats (p < 0.05), as expected. After 30 min of ischemia, there was, in addition, a shortening of the hyperemic response duration. Time to post-ischemic half normalization of arterial conductance was 38 +/- 24 s in the SHRs versus 149 +/- 58 s in the WKY rats (p < 0.001).


CONCLUSIONS
In vivo perfusion measurement not only confirmed the existence of a reduced maximum peripheral vasodilation in chronically hypertensive rats, it revealed a blunted hyperemic response after prolonged ischemia in the SHRs, which might be an important contributing factor to the increased sensitivity to ischemia in hypertension.
Bertoldi
Didier
D
NMR Laboratory, AFM-CEA, Institute of Myology, IFR 14, Pitié-Salpêtrière University Hospital, Paris, France.
Parzy
Elodie
E
Fromes
Yves
Y
Wary
Claire
C
Leroy-Willig
Anne
A
Carlier
Pierre G
PG
D000375:Aging; D000818:Animals; D006614:Hindlimb / Q000098:blood supply; D006940:Hyperemia / Q000503:physiopathology; D006973:Hypertension / Q000503:physiopathology*; D007511:Ischemia / Q000503:physiopathology; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D015427:Reperfusion Injury / Q000503:physiopathology; D013113:Spin Labels; D014664:Vasodilation / Q000502:physiology*
D013113:Spin Labels