Permissive effect of nitric oxide in arachidonic acid induced dilation in isolated rat arterioles

• Published in: Cardiovascular research 1998-06, Vol.38 (3), p.782-787
• Main Authors: BAKKER, E. N. T. P, SIPKEMA, P
• Format: Article
• Language: English
• Subjects: Animals; Arachidonic Acid - metabolism; Arachidonic Acid - pharmacology; Arterioles; Biological and medical sciences; Blood vessels and receptors; Cyclic GMP - analogs & derivatives; Cyclic GMP - pharmacology; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Male; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - metabolism; Myography; Nitric Oxide - physiology; Nitric Oxide Synthase - antagonists & inhibitors; Nitroarginine - pharmacology; Nitroprusside - pharmacology; Penicillamine - analogs & derivatives; Penicillamine - pharmacology; Rats; Rats, Wistar; S-Nitroso-N-Acetylpenicillamine; Vasodilator Agents - pharmacology; Vertebrates: cardiovascular system
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1016/S0008-6363(98)00046-7

Prostaglandins and nitric oxide play an important role in the regulation of arteriolar tone. L-Arginine analogues inhibit nitric oxide formation, but may also inhibit arachidonic-acid induced dilation. Nitric oxide was found to stimulate cyclooxygenase activity in cultured endothelial cells. Therefore, we hypothesized that the non-specific inhibition of prostaglandin-related dilation by L-arginine analogues is a consequence of the absence of nitric oxide. To test this hypothesis, arteriolar segments from rat cremaster muscle were studied in a pressure myograph at 75 mmHg. Segments developed spontaneous tone, the diameter reduced from 179 +/- 3 to 98 +/- 3 microns (n = 41). In this condition, responses to exogenous arachidonic acid (1 microM) were recorded and compared with responses after addition of L-NNA, and addition of either SNAP, nitroprusside or 8-Br-cGMP in the presence of L-NNA. Inhibition of basal nitric oxide production with L-NNA (0.1 mM) reduced arachidonic acid-induced dilation (from 52 +/- 9 to 31 +/- 6 microns). In the presence of L-NNA, responses to arachidonic acid were augmented when exogenous nitric oxide was also present (SNAP, 31 +/- 6 microns vs. 75 +/- 5 microns; nitroprusside, 31 +/- 8 microns vs. 42 +/- 7 microns). Responses were not augmented with the second messenger of nitric oxide-mediated dilation 8-Br-cGMP (37 +/- 9 microns vs. 32 +/- 9 microns). These results indicate that nitric oxide directly increases arachidonic acid-induced dilation. Thus, the non-specific effect of L-arginine analogues can be explained by a permissive effect of nitric oxide on endothelial arachidonic acid metabolism.