Taurine effect on neuritic growth from goldfish retinal explants.

Explants from retinas from which the optic nerve was previously crushed exhibited neuritic outgrowth after 4-5 days in culture, and up to 10 days in the presence of the same nutrient medium. Intact retinas did not exhibit vigorous outgrowth. Taurine added in the medium to post-crush explants accelerated the emission of neurites in 1-2 days, and increased the nerve growth index in a concentration-dependent manner up to 4 mM. Greater concentration did not produce any effect on the nerve growth index. The effect of taurine was produced between 0 and 5 days in culture; from day 5 to day 10 explants did not exhibit further growth in the presence of the amino acid. However, post-crush control explants exhibited growth between 5 and 10 days. Taurine effect is blocked in the absence of fetal calf serum, and is reduced in the presence of dialysed serum. Providing new medium on days 1 and 2, but not later, elevated the nerve growth index with respect to explants regenerating in the same medium since day 0. In addition, taurine supplied at various days after plating produced the same pattern of growth as that observed by adding fresh medium, but the nerve growth index was statistically greater in the presence of the amino acid. The mechanisms for these observations remain to be elucidated.