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. 1994 Jan;111(1):325–331. doi: 10.1111/j.1476-5381.1994.tb14063.x

Effects of NG-nitro-L-arginine methyl ester on regional haemodynamic responses to MgSO4 in conscious rats.

P A Kemp 1, S M Gardiner 1, J E March 1, T Bennett 1, P C Rubin 1
PMCID: PMC1910029  PMID: 8012714

Abstract

1. We assessed regional haemodynamic responses to the vasodilator, MgSO4, in the absence and presence of the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), in conscious chronically instrumented Long Evans rats (n = 9). 2. MgSO4 (loading dose 220 mumol kg-1 min-1 for 7 min, maintenance dose 56 mumol kg-1 min-1 for 7 min), alone, caused slight bradycardia and hypotension accompanied by reductions in renal and mesenteric flows, but a marked hyperaemic vasodilatation in the hindquarters (flow, delta 54 +/- 6%, vascular conductance, delta 77 +/- 5%). 3. L-NAME (183 nmol kg-1 min-1) caused hypertension (29 +/- 2 mmHg) accompanied by bradycardia (-51 +/- 6 beats min-1) and reductions in flow and vascular conductance in the renal (-18 +/- 4% and -35 +/- 3%, respectively), mesenteric (-35 +/- 3% and -49 +/- 3%, respectively), and hindquarters (-26 +/- 3% and -42 +/- 3%, respectively) vascular beds. In the presence of L-NAME, the hypotensive and bradycardic effects of MgSO4 were still apparent, but its hindquarters hyperaemic vasodilator effect was significantly attenuated. 4. In order to determine if the inhibitory action of L-NAME on the hindquarters hyperaemic vasodilator action of MgSO4 was a non-specific effect, due to the change in baseline conditions caused by L-NAME, we also examined responses to MgSO4 in the presence of endothelin-1 (12.5 pmol kg-1 min-1) or angiotensin II (50 pmol kg-1 min-1). In the presence of either peptide, the overall effects of MgSO4 on hindquarters flow and vascular conductance were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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