Unique Pharmacological Interactions of Taurine and Chelerythrine in the Retina

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Abstract
The effects of taurine and chelerythrine (CHT) on ATP-dependent calcium uptake and the phosphorylation of the ~20 kDa phosphoprotein in the retina were compared. In the absence of the CHT, taurine stimulated ATP-dependent calcium uptake and attenuated the phosphorylation of the ~20 kDa phosphoprotein. On the other hand, CHT produced the opposite results in the absence of taurine. When the two agents were used simultaneously, it was found that CHT non-competitively inhibited the action of taurine to stimulate calcium uptake, while taurine non-competitively inhibited the action of CHT to stimulate the phosphorylation of the ~20 kDa phosphoprotein. The data present an unusual pharmacological mechanism for controlling the signal transduction pathway involving the two distinct cellular processes being studied. Given the unique data, a control system is proposed in which the function of the ~20 kDa phosphoprotein is linked to the stimulation of ATP-dependent calcium uptake.