Effect of NG-nitro-L-arginine on pressor action of arginine vasopressin in normotensive (WKY) and spontaneously hypertensive (SHR) rats.
In order to find out whether the pressor effect of arginine vasopressin (AVP) is limited by release of nitric oxide (NO) and whether it is altered in hypertension, blood pressure (MAP) and heart rate (HR) responses to i.v. administration of AVP were compared in conscious normotensive Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats under control conditions and during blockade of NO synthesis induced by i.v. administration of NG-nitro-L-arginine (L-NOARG). In control experiments AVP elicited significant elevations of MAP in WKY and SHR. The maximum increases in WKY and SHR amounted 26 +/- 3 and 16 +/- 3 mmHg, respectively, and did not differ significantly from each other. In WKY increase of MAP was associated with significant bradycardia. Administration of AVP in this strain during blockade of NO synthesis resulted in significantly smaller increase of blood pressure (13 +/- 5 mmHg) than under control conditions (p < 0.001), and in nonsignificant changes of HR. In SHR AVP caused a progressive significant decrease of blood pressure associated with transient tachycardia. The results indicate that blockade of NO synthesis does not enhance but reduces increase of blood pressure in WKY and transforms the pressor action of this peptide into the hypotensive effect in SHR. This phenomenon is discussed in relevance to the possible unfavorable effects of AVP on coronary and/or cerebral circulation during blockade of NO formation.
Styś
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Department of Clinical and Applied Physiology, Medical Academy, Warsaw, Poland.
Szczepańska-Sadowska
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D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019335:Nitroarginine; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D001127:Arginine Vasopressin; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine