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J Am Coll Cardiol. 1997 May;29(6):1332-8.

Myocardial contractile effects of L-arginine in the human allograft.

Author information

1
Cardiovascular Center, O.L.V. Ziekenhuis, Aalst, Belgium.

Abstract

OBJECTIVES:

In the present study, we investigated, in transplant recipients, whether L-arginine (L-arg) potentiates the myocardial contractile effects of receptor-mediated coronary endothelial stimulation. Moreover, because inducible nitric oxide synthase (iNOS) is frequently expressed in transplanted myocardium, we also performed intracoronary infusion of L-arg in the absence of receptor-mediated coronary endothelial stimulation to investigate whether similar left ventricular (LV) contractile effects could be induced by providing more substrate for iNOS.

BACKGROUND:

Nitric oxide (NO), released from coronary endothelium after receptor-mediated stimulation by substance P (SP), affects vascular smooth muscle tone and modulates LV contractile performance. L-arg augments receptor-mediated endothelium-dependent coronary vasodilation in transplant recipients by increasing substrate availability for endothelial NO production.

METHODS:

Sixteen transplant recipients were studied at the time of annual coronary angiography. In eight transplant recipients, microtip LV pressures were recorded before and during intracoronary (IC) SP (20 pmol/min) and after the addition of IC L-arg (160 mumol/min) to IC SP. In eight transplant recipients, microtip LV pressures were recorded before and during IC L-arg (160 mumol/min) alone, and in six of these patients, endomyocardial biopsy samples were obtained to detect the expression of iNOS gene by reverse transcription-polymerase chain reaction.

RESULTS:

Addition of IC L-arg to IC SP induced a fall (mean +/- SEM) in LV peak systolic pressure (-16 +/- 4 mm Hg), which was larger (p < 0.01) than that observed during IC SP (-7 +/- 2 mm Hg). During IC L-arg alone, there was no change in LV peak systolic pressure despite the presence of iNOS mRNA in five of the six biopsy samples.

CONCLUSIONS:

In transplant recipients, L-arg potentiates the paracrine myocardial contractile effects of receptor-mediated coronary endothelial stimulation, probably by providing more substrate for endothelial NO production. Despite the myocardial expression of iNOS gene, L-arg alone fails to elicit similar contractile effects.

PMID:
9137232
DOI:
10.1016/s0735-1097(97)00056-9
[Indexed for MEDLINE]
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