Effect of arginine on cyclosporine-induced systemic hypertension after cardiac transplantation in the young

Endothelial dysfunction and circadian blood pressure rhythmicity in young heart transplant recipients

Blood pressure variability correlates with circadian rhythmicity in endothelium-derived nitric oxide (NO) production in adults. Young, hypertensive orthotopic heart transplant (OHT) patients have functional abnormalities in NO-dependent signaling pathways that lead to reduced NO bioavailability and endothelial dysfunction. Following acute intravenous infusion of L: -arginine, the amino acid substrate for NO, OHT patients normalize blood pressure (BP) and endothelial function. However, the effects of chronic L: -arginine infusion on circadian BP rhythmicity and endothelial function in OHT patients have not been described. Six OHT patients (9-29 years old), and seven healthy control subjects (19-28 years old) were admitted for 48 hours. Systolic, diastolic, and mean blood pressures (MBP) were recorded hourly. Urine samples were obtained to measure nitrates/nitrites (NO(X)). Brachial artery flow-mediated vasodilatation (FMD; an index of endothelial function) and left ventricular ejection fraction (LVEF) were measured 0, 23, and 48 hours after admission. Intravenous L: -arginine HC1 was infused continuously beginning 24 hours after admission in all subjects. The incidence (50%) and degree (12.0 +/- 9.2%) of nocturnal MBP dipping was significantly less in OHT patients than control subjects. Furthermore, FMD was significantly reduced in OHT patients compared to controls (3.2 +/- 1.1 vs 7.2 +/- 3.1%, p = 0.01). L: -Arginine infusion had no significant effect on 24-hour MBP, LVEF, or nocturnal dipping status in any subject; however, L: -arginine normalized FMD in OHT patients (7.4 +/- 1.8%). Circadian BP variability and endothelial function are impaired in young cardiac transplant patients with medically controlled hypertension, and L: -arginine administration reverses endothelial dysfunction.

Long-term dietary L-arginine supplementation attenuates proteinuria and focal glomerulosclerosis in experimental chronic renal transplant failure

Glomerular endothelial nitric oxide synthase expression is decreased in humans during acute rejection and chronic renal transplant failure (CRTF). This may contribute to vascular damage through changes in the renal hemodynamics and enhanced endothelial adhesion of leukocytes and platelets. Dietary supplementation of L-arginine may increase endothelial NO production, thereby protecting the vascular wall and improving renal hemodynamics. We tested the hypothesis that long-term L-arginine supplementation attenuates the development of CRTF in an experimental model for renal transplantation. In the Fisher 344 to Lewis rat model for renal transplantation, renal function and histology of untreated rats was compared with rats receiving L-arginine in the drinking water (10g/L), starting 2 days before transplantation. Every 4 weeks systolic blood pressure was measured and serum and urine were collected for measurement of nitrite and nitrate (NO(x)), creatinine, and proteinuria. At 34 weeks the histological renal damage was assessed by scoring focal glomerulosclerosis and measurement of alpha-smooth muscle actin (alpha-SMA) expression. Urinary NO(x) was significantly increased in treated animals. Proteinuria was significantly lower in L-arginine-treated animals from week 24 onward (p<0.05). Plasma creatinine and creatinine clearance did not differ between the groups. The focal and segmental glomerulosclerosis (FGS) score (max 400) at week 34 was also significantly lower in treated rats arbitrary U (20+/-21 vs 61+/-67 arbitrary U; p<0.05). The expression of alpha-SMA was lower in L-arginine-treated rats than in untreated rats (1.93+/-0.8% area surface vs 3.64+/-2.5% area surface). In conclusion, in this experimental model for CRTF, L-arginine administration significantly reduced FGS and proteinuria, without affecting renal function. Our data suggest that dietary L-arginine supplementation attenuates progression of CRTF and may therefore be an additional therapeutic option in human renal allograft recipients.

Drug treatment of clinical problems related to cardiac transplantation

In recent years, several new immunosuppressive agents have become available for the treatment of cardiac transplant recipients. Use of these agents and their potential side effects are reviewed.