TAURINE RELEASE ASSOCIATED TO VOLUME REGULATION IN RABBIT LYMPHOCYTES

Rabbit lymphocytes exposed to hyposmotic media first swell and then recover their initial volume within 6 min. During volume recovery, free amino acids (FAA) decrease from 451.1 to 208 nmoles/mg protein. Taurine was the dominating FAA, accounting for 70% of the FAA pool. The time course of H-3-taurine release induced by hyposmolarity followed that of volume recovery. Efflux of H-3-taurine in an 8 min period was 17.8% (of total labeled taurine accumulated during loading) in an isosmotic medium. Reducing osmolarity ot 0.87, 0.75, 0.62, and 0.5 increased this release to 24.8%, 38.1%, 56.4% and 70.9%, respectively. The volume-sensitive release of H-3-taurine was unaffected by omission of external Na+ or Ca++ and was reduced by 23% in the absence of Cl-. It was unaffected by agents disrupting the cytoskeleton or by tetraethylammonium, barium, quinidine, and gadolinium, but was 26% reduced by DIDS. Taurine release was inhibited at 4-degrees-C, but was unchanged at 15-degrees-C or 25-degrees-C. An involvement of FAA, particularly taurine, in lymphocyte volume regulation is suggested.