Embryonic exposure to high taurine: a possible nutritional contribution to Friedreich's ataxia.

When fertilized eggs (50 g) are injected on day 1 with 100 mumol taurine (0.2 ml), 15-day-old embryos exhibit increased taurine content in heart and brain. Lethal toxicity was no higher than with equimolar injections of NaCl (50 mumol) or valine (100 mumol) of the same volume. That same dose of taurine injected either on embryonic day 1 or 7 produced in hatchlings a typical syndrome of ataxia, reduced muscle strength and motor incoordination. When injected on embryo day 15 (E15) most chicks appeared incapable of pecking out of the egg, and the resulting delay in hatching, if if did occur, precluded presuming that the poor condition of such chicks was exclusively due to the late taurine injections. In view of the tendency of Friedreich's ataxia patients to exhibit increased alimentary absorption of taurine, and to demonstrate an excessive accumulation of taurine in the cerebellum and heart tissue on autopsy, fetal exposure to high taurine levels or neonatal high taurine milk ingestion may, by analogy, contribute to the slowly progressing disease process.