What effect would ingesting isotonic saline have on plasma ADH levels? Explain the physiological mechanisms involved

Question

Answer 1

To answer your question, one needs to understand that increased Plasma Osmolarity and decreased Blood Volume Stimulate ADH Release. High ADH increases the reabsorption of water and produces a low volume of highly concentrated urine.

The study conducted by Tanaka et al1 found that Plasma ADH levels were clearly affected by the small changes in blood volume, and a significantly negative correlation was found between plasma ADH levels and the percent changes in blood volume under isotonic circumstances. I hope this answers your question.

Reference

1. Tanaka S, Shimamoto K, Takada T, Nishitani T, Ando T, Iimura O. The effect of blood volume changes accompanying isotonic circumstances on plasma antidiuretic hormone levels in normal subjects. Japanese journal of medicine. 1985;24(1):30-33. doi:10.2169/internalmedicine1962.24.30