GALT deficiency causes UDP-hexose deficit in human galactosemic cells

Previously we reported that stable transfection of human UDP-glucose pyrophosphorylase (hUGP2) rescued galac-tose-1-phosphate uridyltransferase (GALT)-deficient yeast from ``galactose toxicity.' ' Here we test in human cell lines the hypothesis that galactose toxicity was caused by excess accumulation of galactose-1-phosphate (Gal-1-P), inhibition of hUGP2, and UDP-hexose deficiency. We found that SV40-transformed fibroblasts derived from a galactosemic patient accumulated Gal-1-P from 1.2 0.4 to 5.2 0.5 mM and stopped growing when transferred from 0.1 % glucose to 0.1 % galactose. Control fibroblasts accumulated little Gal-1-P and continued to grow. The GALT-deficient cells had 157 10 mmoles UDP-glucose/100 g protein and 25 5 mmoles UDP-galactose/100 g protein when grown in 0.1% glucose. The control cells had 236 25 mmoles UDP