[Plasma level of atrial natriuretic peptide following oral glycerol administration]

Atrial natriuretic peptide (ANP) is a cardiac hormone known to mediate increased capillary permeability, vasodilation, and natriuresis. In 1988 the authors' experimental results indicated the presence of ANP receptors in the inner ear. From this they hypothesized that ANP might be involved in the regulation of inner ear fluids and therefore investigated the effects of orally administered glycerol on ANP and cGMP plasma levels. As regards the initial values, there was no apparent significant difference between the 14 subjects with Ménière's disease and the 34 subjects without. During the first hour after glycerol administration there was a significant hormonal effect: ANP, cGMP (second messenger), and serum osmolality increased, while total serum protein and plasma renin decreased. In addition to this, the hearing ability of ten subjects was positively affected. After the first hour the hormonal levels reapproached their original homeostatic states. But the positive effects on hearing ability continued to increase for another hour before decreasing again. The authors believe that this delayed effect is caused by the blood-perilymph barrier. Further research is required to establish whether glycerol affects hearing improvement directly or by mobilizing ANP.