Platelet taurine in Down's syndrome.

Endogenous platelet taurine and uptake of radioactively labelled taurine by platelets was measured in normal, non-mongoloid and mentally retarded mongoloid trisomy 21 subjects. Endogenous taurine was normal in all groups, while taurine transport kinetic experiments showed normal Km but reduced Vmax in mongoloid trisomy 21 and mentally retarded patients. The latter difference may be due to decreased metabolism following decreased enzyme protein synthesis.