Inhibitory and stimulatory effects of structural and conformational analogues of taurine on ATP-dependent calcium ion uptake in the rat retina: deductions concerning the conformation of taurine.
A number of novel analogues of taurine were tested in a rat retinal preparation for their stimulatory or inhibitory activity in the ATP-dependent calcium ion uptake system at low calcium ion concentration. While the structural requirements for maintaining biological activity were quite limited, certain sulfone derivatives of taurine were observed to be more potent stimulators of calcium ion uptake than taurine. Utilization of multiple effectors in the uptake system was also analyzed. The effects of all combinations of taurine plus analogue that were tested were demonstrated to be mutually exclusive, that is, the compounds have similar modes of action. When two inhibitors, TAPS and THQS, were tested in combination, kinetic evaluation of the data suggested that both of these compounds also have a similar mode of action (mutually exclusive) with respect to each other. The inhibitors, TAPS and THQS, were also observed to be non-competitive with respect to taurine thus suggesting that they do not bind to the same site as taurine.
Lombardini
J B
JB
Department of Pharmacology, Texas Tech University Health Sciences Center, Lubbock 79430.
Liebowitz
S M
SM
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D008968:Molecular Conformation; D015394:Molecular Structure; D051381:Rats; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D013654:Taurine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology
D013654:Taurine; D000255:Adenosine Triphosphate; D002118:Calcium