Mc. Ortiz et al., IMPORTANCE OF NITRIC-OXIDE AND PROSTAGLANDINS IN THE CONTROL OF RAT RENAL PAPILLARY BLOOD-FLOW, Hypertension, 27(3), 1996, pp. 377-381
The role of nitric oxide and prostaglandins in the control of rat rena
l papillary blood flow has been studied in anesthetized Munich-Wistar
rats by use of laser Doppler flowmeter. Acute administration of N-omeg
a-nitro-L-arginine methyl ester (L-NAME) 10 mg/kg IV (n=8) increased m
ean arterial pressure by 27.8+/-3.6%, decreased papillary blood flow b
y 39.4+/-3.8%, and decreased renal blood flow by 47.4+/-1.9%. The subs
equent administration of indomethacin (7.5 mg/kg IV) further decreased
papillary blood flow (35.2+/-2.5%) without significant changes in mea
n arterial pressure or renal blood flow. In a second group (n=6), admi
nistration of indomethacin before L-NAME decreased papillary blood flo
w by 39.6+/-2.1% without significantly altering mean arterial pressure
or renal blood Row. The subsequent injection of L-NAME further decrea
sed papillary blood flow (32.9+/-1.8%) and renal blood flow (49.8+/-6.
6%) while increasing mean arterial pressure to a level not significant
ly different from that found in the first group. Autoregulation studie
s showed that L-NAME but not indomethacin reduced the renal perfusion
pressure-renal blood flow relationship without altering autoregulation
. However, both nitric oxide and prostaglandins importantly affected t
he renal perfusion pressure-papillary blood flow relationship because
L-NAME and indomethacin significantly decreased this relationship in a
n additive fashion. Although both drugs reduced the sensitivity of the
pressure-papillary Row relationship, only L-NAME affected autoregulat
ion so that papillary blood flow was autoregulated at higher renal per
fusion pressures. Thus, the present results indicate that both nitric
oxide and prostaglandins control a similar percentage of rat renal pap
illary blood flow, but nitric oxide seems to be more important than pr
ostaglandins as a mediator of the pressure-blood flow relationship. In
contrast, only nitric oxide modifies the renal blood flow level, alth
ough it does not disturb whole-kidney blood flow autoregulation.