Potassium‐stimulated release of taurine from cultured cerebellar granule neurons is associated with cell swelling

Abstract

Effects of increased concentrations of potassium and of hyposmolar conditions on release of taurine were investigated in cerebellar granule neurons cultured from mice. It was found that increases in the external potassium concentration as well as decreases in osmolarity dose‐dependently increased release of exogenously supplied [³H]‐taurine and endogenous taurine from the neurons. The release of endogenous taurine elicited by a reduction of the osmolarity of the incubation media to 70% or 50% was much more pronounced than that of other amino acids, particularly glutamine, the release of which was not affected at all. The potassium‐stimulated release of [³H]‐taurine was strictly chloride dependent and it was inhibited by an increase of the osmolarity of the media as well as by 4,4′‐diisothyocyanostilbene‐2,2′‐disulfonate (DIDS) (100 μM). Moreover, a similar increase in the potassium concentration led to an increase in intracellular volume (swelling), a process which was also chloride dependent. It is concluded that potassium‐stimulated taurine release from cerebellar granule neurons is associated with cell volume changes and that taurine is likely to play a role as an osmotically active substance in these neurons.