ASSOCIATION OF THE PLASMA ARG/ADMA RATIO WITH THE SALT-SENSITIVITY: PP.9.370

Abstract

Objectives: Asymmetric dimethylarginine (ADMA) is the unique endogenous inhibitor of the NO synthases. As NO plays important roles both in the regulation of the systemic vascular tone and of salt excretion in the kidney, ADMA may be a key player in the regulation of salt-sensitivity. In this communication, we explored the relation of ADMA with the salt-sensitivity in Africans by a salt-loading experiment on volunteers. Design and Method: Thirthy-one Tanzanian male healthy volunteers without hypertension (25–35 years old) were recruited for the experiment. A salt-loading experiment was performed following the protocol designed previously (Hypertens Res 2002;25:809). Briefly, the participants ingested 140mEq/day NaCl additional to their normal diet (containing about 85mEq/day NaCl) in the first week and then took 25 mg/day hydrochlorthiazide (without the salt-loading) in the second week. Blood sampling and blood pressure (BP) measurement was performed at the entry, on the 4th and 7th days of the each week. L-arginine (Arg), ADMA and symmetric dimethylarginine (SDMA) were measured in plasma with HPLC. All the participants gave an informed consent. Results: The change in the mean BP (δMBP) between the salt-loading and the diuretic phase showed a biphasic distribution; the participants with a larger δMBP were defined as a salt-sensitive group (SS, δMBP = -7.3 ± 2.7mmHg, n = 8) while the others were as a salt-resistant group (SR, δMBP = 3.4 ± 4.2mmHg, n = 23). The basal level of ADMA was significantly greater in SS than in SR (SS:0.57 ± 0.09mmol/L, SR: 0.49 ± 0.06mmol/L, p = 0.006) although it was quite stable either in the salt-loading or in the diuretic phase. The increase in the Arg/ADMA ratio from the salt-loading to the diuretic phase (δArg/ADMA_diuret-salt) was significantly greater in SS than in SR (p = 0.04). δArg/ADMA_diuret-salt showed an clear inverse correlation with δMBP (r = -0.53, p = 0.002). The multiple regression analysis confirmed the independent effect of δArg/ADMA_diuret-salt with other factors of the basal ADMA level and the change in the serum Chloride level. Conclusions: The plasma Arg/ADMA ratio was found to be related to the salt-sensitivity in healthy African males.