Recent experiments showed that in a one-bottle test conducted 16h after sc injection of
polyethylene glycol (PEG)
solution,
hypovolemic rats consumed
water or 0.30 M
NaCl in an initial drinking episode but did not empty the
ingested fluid from the
stomach or absorb it from the
small intestine very rapidly, certainly not as rapidly as when 0.15M
NaCl was consumed (Smith et al., Am J Physiol 292: R2089-R2099, 2007). The present experiments examined the patterns of
water and 0.30 M
NaCl ingestion and the movement of consumed fluid through the
gastrointestinal tract when PEG-treated rats were given a two-bottle delayed-access test. We found that both fluids always were consumed in the first drinking episode, that the fluid mixture
ingested was equivalent to 0.10-0.15M
NaCl, and that
gastric emptying rate and net fluid absorption from the
small intestine usually were much faster than when PEG-treated rats drank either
water or
hypertonic saline alone. Thus,
ingestion of
water and 0.30 M
NaCl by
hypovolemic rats in the same episode adaptively facilitated the movement into the circulation of a near-isotonic fluid that is ideal for restoring plasma volume deficits.
