Measurement of changes in cerebral blood volume in spontaneously hypertensive rats following L-arginine infusion using dynamic susceptibility contrast MRI.
To understand whether the NO-dependent vasodilator L-arginine was effective upon a chronically hypertensive cerebral capillary endothelium, dynamic susceptibility contrast MRI was used to measure the relative cerebral blood volume (rCBV) changes in nonischemic spontaneously hypertensive rats (SHRs). rCBV was measured in 11 rats at 4.7 T using fast gradient echo imaging with intravenous injection of Gd-DTPA. Images were acquired before, immediately after, and up to 90 min after the infusion of 300 mg/kg L-arginine (n = 7) or of an equivalent volume of saline (n = 4). L-arginine increased rCBV in cortex beginning 10 min after infusion and reached significance after 30 min (P < 0.01), reached a peak of 1.24 +/- 0.06 (mean +/- SEM) times pre-injection level after 50 min, and was sustained throughout the 90 min observation period. In contrast, the rCBV in the deeper gray matter (striatum) showed no statistically significant change over the 90 min observation period. While this is consistent with previous studies showing that L-arginine infusion can directly modulate vascular tone and cerebral hemodynamics, it demonstrates that the effect is present only in cortex, and that it can occur also in the setting of a disturbed capillary endothelium.
Caramia
F
F
MGH-NMR Center, Department of Radiology, Massachusetts General Hospital, Charlestown 02129, USA.
Yoshida
T
T
Hamberg
L M
LM
Huang
Z
Z
Hunter
G
G
Wanke
I
I
Zaharchuk
G
G
Moskowitz
M A
MA
Rosen
B R
BR
D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D001810:Blood Volume / Q000187:drug effects; D001921:Brain / Q000098:blood supply* / Q000187:drug effects*; D003287:Contrast Media; D004195:Disease Models, Animal; D019786:Gadolinium DTPA; D006439:Hemodynamics / Q000187:drug effects; D006974:Hypertension, Malignant / Q000188:drug therapy* / Q000503:physiopathology; D007262:Infusions, Intravenous; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009569:Nitric Oxide / Q000096:biosynthesis; D051381:Rats; D011918:Rats, Inbred SHR; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects; D013997:Time Factors
D003287:Contrast Media; D009569:Nitric Oxide; D001120:Arginine; D019786:Gadolinium DTPA