Hypotaurine uptake by the retina.

A study of the transport of 3H-hypotaurine by rat retina has been carried out. The process is markedly sodium and temperature dependent. Kinetic analysis of the data revealed two values for the affinity constant (K) of 4.91 microM and 1,071.3 microM. Some related and unrelated amino acids were examined as competitive inhibitors of 3H-hypotaurine transport. Only GABA and beta-alanine exhibited appreciable inhibitory activity. Taurine, glycine, and guanidine ethane sulfonate were not inhibitors. 3H-hypotaurine uptake was similarly distributed in the retinal subcellular fractions P1 and P2. The active uptake of 3H-hypotaurine by retinas of the rat and other species including chick and frog was studied and compared to cerebral cortex slices. The chick retina was similar to the rat in its capacity to transport hypotaurine whereas frog exhibited fourfold less activity. Slices of cerebral cortex from rat and chick exhibited hypotaurine uptake but again the magnitude of the transport was three to fourfold less than in the comparative retinas.