SALT-REGULATING HORMONES IN YOUNG NORMOTENSIVE OBESE SUBJECTS - EFFECTS OF SALINE LOAD

To investigate whether the response of salt-regulating hormones to vol ume expansion is impaired in obese subjects, we assessed the effects o f saline load (0.25 mL/kg.min.120 min) in 9 young, increased more in l ean than obese subjects during saline load. Comparisons of percent cha nges in ANF, PRA, and PA after saline load showed that the responses o f lean and obese subjects were significantly different (P<.001 for ANF at both 60 and 120 minutes; P<.05 for PRA and PA at both 60 and 120 m inutes). In conclusion, the lack of ANF response and the reduced suppr ession of PRA and PA to saline load indicate a dysfunction of these sy stems in obese subjects. This alteration may be involved in the higher susceptibility of obese subjects to developing hypertension. healthy, normotensive obese subjects (body mass index, >30 kg/m(2)) and in 10 lean control subjects (body mass index, <25 kg/m(2)) matched for age, gender, height, and mean blood pressure. Hematocrit, plasma renin acti vity (PRA), plasma aldosterone (PA), atrial natriuretic factor (ANF), and urinary sodium excretion (UN,V) were evaluated. Saline load increa sed ANF levels significantly (P<.001) in lean subjects at both 60 and 120 minutes, whereas they decreased in obese subjects. Such decreases became significant (P<.01) at 120 minutes. Suppression of PRA and PA b y saline load were more marked in lean than obese subjects. Hematocrit decreased in both groups, and UN,V increased more in lean than obese subjects during saline load. Comparisons of percent changes in ANF, PR A, and PA after saline load showed that the responses of lean and obes e subjects were significantly different (P<.001 for ANF at both 60 and 120 minutes; P<.05 for PRA and PA at both 60 and 120 minutes). In con clusion, the lack of ANF response and the reduced suppression of PRA a nd PA to saline load indicate a dysfunction of these systems in obese subjects. This alteration may be involved in the higher susceptibility of obese subjects to developing hypertension.