Arginine (ARG) supplementation (5% arginine in chow) restores plasma ARG levels in S+S-Antilles mice to that found in C57BL mice and is associated with a reduction in Ca++ activated K+ channel (Gardos channel) activity, MCHC and high density red cells (Romero, Blood 99(4):2002). However the mechanisms for these effects are not entirely clear. Endothelin-1 (ET) is a potent vasoconstrictor that has been shown to activate Gardos channel activity and reduce MCHC. We hypothesized that reduced ET could account for the decrease in Gardos channel activity. We report here that arginine diet reduced ET levels in mouse plasma from 137 ± 10 to 89 ± 17 pmol/ml using a modified HPLC technique originally proposed by Kumarathasan (

Anal Biochem 299:37, 2001
). We measured Gardos channel activity in ex vivo red cells as the influx of 86Rb in the presence or absence 10μM clotrimazole. Consistent with our previous report, we observed that ARG supplementation was associated with a decrease in Gardos Channel activity. In addition, incubation of red cells with 500 nmol/L of ET for 15 min at 37°C stimulated an increase in Gardos channel activity in cells from both ARG supplemented vs non-supplemented mice that was sensitive to 1 mmol/L of the specific ET receptor B antagonist, BQ788 (9.4 ± 2.5 vs 14.6 ± 3.8 mmol/L cell x h, respectively). However, the maximal response of the Gardos channel activity to ET was significantly blunted in ARG supplemented vs non-supplemented mice (15.7 ± 2.8 vs 22.1 ± 2.2 mmol/L cell x h, p<0.03, n=5). We also performed QT-RT PCR using Taqman assays on aortas from these mice and observed that mRNA expression of both ET and ET receptor A levels were significantly decreased in ARG supplemented vs non-supplemented mice (p<0.05, n=5) while ET receptor B levels were not significantly affected (n=5). Thus, our results suggest that reduced ET is in part responsible for the blunted Gardos channel activity in arginine supplemented mice and raises the possibility that ET metabolism is modulated by arginine supplementation. We conclude that arginine supplementation of sickle cell patients may have multiple benefits including reduced polymer formation, reduced vasoconstriction, and reduced inflammatory response.

Topics:
arginine, diet, endothelins, mice, transgenic, mean corpuscular hemoglobin concentration determination, antagonists, clotrimazole, endothelin-1, high pressure liquid chromatography procedure, polymerase chain reaction

Author notes

Disclosure: No relevant conflicts of interest to declare.

2007, The American Society of Hematology
2007
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