Astrocytes and lymphocytes are able to release significant amounts of
taurine during periods of hypotonicity to reduce the increase in cell
volume. To investigate this mechanism in the liver, we studied the rel
ease of free amino acids from isolated perfused rat liver during hypot
onicity. The osmolarity of the perfusion medium was reduced from 305 t
o 255 or 205 mosM by decreasing the NaCl concentration 25 or 50 mM, re
spectively. This induced an 6-8% increase in liver mass and was associ
ated with a specific 1.7-fold (-50 mosM) and 14-fold (-100 mosM) incre
ase of the taurine release. None of the other amino acids measured sho
wed a significant increase in their concentration in the effluent. The
increase in taurine release occurred within 30 s after exposure to hy
potonicity (maximal after 1-1.5 min) and followed closely the changes
in liver mass. The taurine release declined gradually during successiv
e exposures of the isolated liver to -100 mosM. This release was 29 an
d 17% of the original during the second and third exposure, respective
ly.