The role of nitric oxide in the peripheral vasoconstriction caused by human placental lactogen in anaesthetized pigs
Regional intra-arterial infusion of human placental lactogen in anaesthetized pigs has been shown to cause coronary, renal and iliac vasoconstriction by antagonizing the vasodilatory effects of β 2 -adrenergic receptors. Since nitric oxide is known to modulate or mediate β 2 -adrenergic effects, t...
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Veröffentlicht in: | Experimental physiology 2006-05, Vol.91 (3), p.603-610 |
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Zusammenfassung: | Regional intra-arterial infusion of human placental lactogen in anaesthetized pigs has been shown to cause coronary, renal
and iliac vasoconstriction by antagonizing the vasodilatory effects of β 2 -adrenergic receptors. Since nitric oxide is known to modulate or mediate β 2 -adrenergic effects, the present study was planned in the same experimental model to determine the role of nitric oxide in
the above vascular responses to human placental lactogen. In eight pigs anaesthetized with sodium pentobarbitone, changes
in anterior descending coronary, left renal and left internal iliac blood flow caused by intra-arterial infusion of human
placental lactogen at constant heart rate and arterial blood pressure were assessed using electromagnetic flowmeters. Intra-arterial
infusion of the human placental lactogen caused decreases in coronary, renal and iliac blood flow which, respectively, averaged
16.7, 8.1 and 12.2% of the baseline values. The role of nitric oxide in this response was studied in the same pigs by repeating
the experiments, after measured blood flows had returned to baseline values, following intra-arterial administration of N Ï -nitro- l -arginine methyl ester ( l -NAME). The subsequent intra-arterial infusion of human placental lactogen did not cause any significant changes in measured
blood flows, even when performed after reversing the increase in arterial blood pressure and coronary, renal and iliac resistance
caused by l -NAME with continuous intravenous infusion of papaverine. These results indicate that the coronary, renal and iliac vasoconstriction
caused by human placental lactogen, known to involve antagonism of β 2 -adrenergic vasodilatory effects, was mediated by inhibition of nitric oxide release. |
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ISSN: | 0958-0670 1469-445X |
DOI: | 10.1113/expphysiol.2005.032755 |