CHANGES IN BLOOD-PRESSURE AND IN VASOACTIVE AND VOLUME REGULATORY HORMONES DURING SEMISTARVATION IN OBESE SUBJECTS

The mechanisms underlying the reduction in blood pressure that occurs with a severe energy-restricted diet were evaluated in 12 obese subjec ts during 8 days on a very-low-calorie diet (1.67 MJ/d) with a constan t intake of 17 mmol sodium per day. The relationship between changes i n blood pressure, sodium balance, plasma volume, renin-aldosterone and sympathetic nervous system activities, plasma C-terminus and N-termin us of the atrial natriuretic factor (ANF) prohormone, brain natriureti c peptide (BNP), and endothelin-1 (ET-1) concentrations was investigat ed. A negative sodium balance was present throughout the diet and was associated with a moderate reduction in plasma volume, a marked activa tion of the renin-aldosterone system, and a concomitant reduction in C -and N-terminal ANF prohormone levels. Moreover, the postural changes in N-terminal proANF and ANF secretion documented before the diet, dis appeared after 8 days of dieting, in contrast to a greater postural st imulation of aldosterone and renin. A negative correlation was found b etween the changes of C-and N-terminal ANF prohormone levels and those of aldosterone. Urinary catecholamine excretion, BNP, and ET-1 remain ed unchanged. These results indicate that the decrease in blood pressu re occurring during severe caloric restriction was essentially due to the reduction in the effective blood volume, as reflected by the stimu lation of the renin-aldosterone system and the decrease in ANF levels. The lack of any changes in catecholamine excretion and endothelin lev els suggests that peripheral vascular resistance did not change signif icantly in these circumstances. Copyright (C) 1998 by W.B. Saunders Co mpany.