Temporal variation in endotoxin‐induced vascular hyporeactivity in a rat mesenteric artery organ culture model

• Published in: British journal of pharmacology 2001-06, Vol.133 (3), p.351-360
• Main Authors: O'Brien, A J, Wilson, A J, Sibbald, R, Singer, M, Clapp, L H
• Format: Article
• Language: English
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Animals; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cyclooxygenase 2; Dose-Response Relationship, Drug; Drug Synergism; endothelium; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; endotoxin; Guanosine Monophosphate - metabolism; Guanylate Cyclase - antagonists & inhibitors; guanylyl cyclase inhibition; Isoenzymes - antagonists & inhibitors; Lipopolysaccharides - pharmacology; Male; Medical sciences; Mesenteric Arteries - drug effects; Mesenteric Arteries - physiology; Miscellaneous; Models, Animal; nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Donors - pharmacology; Nitric Oxide Synthase - antagonists & inhibitors; Nitrobenzenes - pharmacology; NOS inhibitors; organ culture; Organ Culture Techniques; Penicillamine - analogs & derivatives; Penicillamine - pharmacology; phenylephrine; Phenylephrine - pharmacology; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Sprague-Dawley; Sulfonamides - pharmacology; thromboxane A2; Time Factors; vascular hyperactivity; Vascular hyporeactivity; Vasoconstriction - drug effects; Vasoconstrictor Agents - pharmacology
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704079

Endotoxin‐induced vascular hyporeactivity to phenylephrine (PE) is well described in rodent aorta, but has not been investigated in smaller vessels in vitro. Segments of rat superior mesenteric artery were incubated in culture medium with or without foetal bovine serum (10%) for 6, 20 or 46 h in the presence or absence of bacterial lipopolysaccharide (LPS; 1 – 100 μg ml−1). Contractions to PE were measured with or without nitric oxide synthase (NOS) inhibitors: L‐NAME (300 μM), aminoguanidine (AMG; 400 μM) 1400W (10 μM) and GW273629 (10 μM); the guanylyl cyclase inhibitor, ODQ (3 μM); the COX‐2 inhibitor, NS‐398 (10 μM). Contractile responses to the thromboxane A2 mimetic, U46619 were also assessed. In the presence of serum, LPS induced hyporeactivity at all time points. In its absence, hyporeactivity only occurred at 6 and 20 h. L‐NAME and AMG fully reversed hyporeactivity at 6 h, whereas they were only partially effective at 20 h and not at all at 46 h. In contrast partial reversal of peak contraction was observed with 1400W (62% at 46 h), GW273629 (57% at 46 h) and ODQ (75% at 46 h). COX‐2 inhibition produced no reversal. In contrast to PE, contractions to U46619 were substantially less affected by LPS. We describe a well‐characterized reproducible model of LPS‐induced hyporeactivity, which is largely mediated by the NO‐cyclic GMP‐dependent pathway. Importantly, long‐term (2‐day) production of NO via iNOS is demonstrated. Moreover, conventional doses of L‐NAME and AMG became increasingly ineffective over time. Thus, the choice of inhibitor merits careful consideration in long‐term models. British Journal of Pharmacology (2001) 133, 351–360; doi:10.1038/sj.bjp.0704079