Estrogen ameliorates Nomega-nitro-L-arginine methyl ester-induced blood pressure increment in male spontaneously hypertensive rats: the role of cGMP.
Estrogen (17beta-estradiol, or E2) reduces systolic blood pressure (SBP) increment and increases aortic cyclic guanosine monophosphate (cGMP) in male spontaneously hypertensive rats (SHRs). It is unknown, however, whether the E2-enhanced aortic cGMP is essential for the BP-lowering effect or not. Nomega-nitro-L-arginine-methyl ester (L-NAME), an L-arginine analogue and nitric oxide (NO) synthase inhibitor, significantly increases SBP and decreases aortic cGMP in male SHRs. We thus treated male SHRs with vehicle (corn oil) or E2 (s.c, 2 mg/kg/week) with or without L-NAME (20 mg/dl in the drinking water). SBP was measured weekly. Plasma nitrate/nitrite (NOx) concentrations and aortic cGMP levels were all measured at the end of the study. We found that SBP increment was significantly higher in L-NAME group, compared with the controls, and that E2 treatment reduced this L-NAME effect. Plasma 4NOx concentrations were not significantly different among different groups. Basal and acetylcholine-induced aortic cGMP, but not sodium nitroprusside-induced cGMP, were significantly lower in L-NAME group, compared with the controls. E2 co-administration did not modify L-NAME-induced aortic cGMP decrease. These data indicate that E2-induced BP-lowering effect in L-NAME treated male SHRs is not closely associated with the enhancement of vascular cGMP.
Yen
Chia-Hung
CH
Department of Physiology and Pharmacology, Chang Gung University College of Medicine Taoyuan 333, Taiwan, ROC.
Wang
Yu-Ren
YR
Huang
Chiu-Feng
CF
Lau
Ying-Tung
YT
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects*; D006152:Cyclic GMP / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009566:Nitrates / Q000097:blood; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009573:Nitrites / Q000097:blood; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D014665:Vasodilator Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009566:Nitrates; D020030:Nitric Oxide Donors; D009573:Nitrites; D014665:Vasodilator Agents; D009599:Nitroprusside; D004958:Estradiol; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester