Similar properties of taurine release induced by potassium and hyposmolarity in the rat retina.
Increasing external K+ concentration to 56, 75 or 100 mM stimulated taurine release by 3-, 7- and 11-fold, respectively. The K(+)-evoked release of [3H]taurine was markedly delayed, sustained and Ca(2+)-independent, in clear contrast to the usual neurotransmitter release pattern. These high K+ concentrations caused a marked increase in retinal cell volume which was prevented by removal of Cl-, or in hyperosmotic solutions. In these conditions [3H]taurine release also was abolished, suggesting an association of taurine efflux and cell swelling. Taurine release was also markedly increased 10- and 20-fold upon reduction of external osmolarity by 25 and 50%, respectively. Both, K(+)- and hyposmolarity-induced release were markedly inhibited by DIDS and quinidine. Total inhibition of the K(+)-evoked release was observed at 200 microM DIDS or 1 mM quinidine, whereas the drugs inhibited the hyposmolarity-evoked release by 50 and 68% respectively, at these concentrations. It is suggested that swelling is the signal for the K(+)-induced taurine release from rat retina.
Departamento de Neurociencias, Universidad Nacional Autónoma de México, D.F.
J
J
Morán
S
S
Hurtado
H
H
Pasantes-Morales
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology*; D011802:Quinidine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013654:Taurine / Q000378:metabolism*; D013997:Time Factors
D002712:Chlorides; D013654:Taurine; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D011802:Quinidine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium