Effect of HEPES on the Na+,Cl-dependent uptake of taurine and beta-alanine by cultured glial cells. Modulation by composition and osmolarity of medium.

The effect of HEPES on the Na+,Cl-dependent uptake of taurine and beta-alanine by cultured glial cells was investigated. Whatever the culture medium used, a similar inhibition of the uptake of taurine by HEPES was found. In a previous paper it was shown that this buffer was able to inhibit the uptake of taurine through a slow and a fast "mechanism", when present in the culture or in the incubation medium, respectively. Comparison of the effect of HEPES on the uptake of taurine and beta-alanine suggested that only the slow "mechanism" was common to the uptake of the beta-aminoacid. Therefore, the uptake of the beta-aminoacid might be affected by HEPES. On the other hand, a small increase of the osmolarity of the media altered the uptake of taurine, suggesting that caution is needed when interpreting pharmacological experiments.