Taurine analogues as modifiers of the accumulation of45calcium ions in a rat retinal membrane preparation

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Abstract
The effects of a series of taurine analogues on the accumulation of 45calcium ions in a crude rat retinal membrane preparation are reported. 45Calcium ion accumulation was measured at high (1.4 mM) calcium ion concentration in the presence and absence of ATP. In the absence of ATP, taurine and α-sulfo-β-ala-nine both inhibit 45calcium ion accumulation. α-Sulfo-β-alanine is the more potent of the two compounds (50% vs. 30% inhibition at 20 mM). The trans aminocycloalkanesulfonic acid analogues of taurine [(±)trans-2-aminocyclopen-tanesulfonic acid and (±)trans-2-aminocyclo-hexanesulfonic acid] are stimulators (3- to 4-fold) of 45calcium ion accumulation. In the presence of ATP (1.2 mM), taurine and the analogues of taurine had no effect. Structure-activity-relationships of these compounds pertinent to their effects on 45calcium ion accumulation at a high calcium ion concentration and in the absence of ATP are discussed. In addition, the inhibitory effects of taurine on 45calcium accumulation in subfractions of the retina (rod outer segments, synaptosomes, and mitochondria) and the effects of the divalent ionophore A23187 on 45calcium accumulation were also investigated.