Advertisement

Amino Acids

, Volume 15, Issue 1–2, pp 99–108 | Cite as

Pharmacological characterization of the effects of taurine on calcium uptake in the rat retina

  • J. D. Militante
  • J. B. Lombardini
Full Papers

Summary

Taurine is known to increase ATP-dependent calcium ion (Ca2+) uptake in retinal membrane preparations and in isolated rod outer segments (ROS) under low calcium conditions (10μM) (Pasantes-Morales and Ordóñez, 1982; Lombardini, 1991). In this report, ATP-dependent Ca2+ uptake in retinal membrane preparations was found to be inhibited by 5μM cadmium (Cd2+), suggesting the involvement of cation channel activation. The activation of cGMP-gated cation channels, which are found in the ROS, is a crucial step in the phototransduction process. An inhibitor of cGMP-gated channels, LY83583, was found to inhibit taurine-stimulated ATP-dependent Ca2+ uptake but had no effect on ATP-dependent Ca2+ uptake in the absence of taurine, indicating that taurine may be increasing ATP-dependent Ca2+ uptake through a mechanism of action involving the opening of cGMP-gated channels. The activation of cGMP-gated channels with dibutyryl-cGMP and with phosphodiesterase inhibition using zaprinast caused an increase in ATP-dependent Ca2+ uptake in isolated ROS, but not in taurine-stimulated ATP-dependent Ca2+ uptake. LY83583 had the same effects in isolated ROS as in retinal membrane preparations. Another inhibitor of cGMP-gated channels, Rp-8-Br-PET-cGMPS, produced the same pattern of inhibition in isolated ROS as LY83583. Thus, there appears to be a causal link between taurine and the activation of the cGMP-gated channels in the ROS under conditions of low calcium concentration, a connection that suggests an important role for taurine in the visual signalling function of the retina.

Keywords

Amino acids Calcium uptake Taurine Rod outer segments cGMP-gated channels 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Baylor D (1996) How photons start vision. Proc Natl Acad Sci USA 93: 560–565Google Scholar
  2. Bean BP (1989) Classes of calcium channels in vertebrate cells. Annu Rev Physiol 51: 367–384Google Scholar
  3. Carbone E, Swandulla D (1989) Neuronal calcium channels: kinetics, blockade and modulation. Prog Biophys Mol Biol 54: 31–58Google Scholar
  4. Cote RH, Brunnock MA (1993) Intracellular cGMP concentration in rod photoreceptors is regulated by binding to high and moderate affinity cGMP binding sites. J Biol Chem 268: 17190–17198Google Scholar
  5. Finn JT, Grunwald ME, Yau K-W (1996) Cyclic nucleotide-gated ion channels: an extended family with diverse functions. Annu Rev Physiol 58: 395–426Google Scholar
  6. Gillespie PG, Beavo JA (1989) Inhibition and stimulation of photoreceptor phosphodiesterases by dipyridamole and M&B 22,948. Mol Pharmacol 36: 773–781Google Scholar
  7. Kuo C-H, Miki N (1980) Stimulatory effect of taurine on Ca-uptake by disc membranes. Biochem Biophys Res Commun 94: 646–651Google Scholar
  8. Leinders-Zufall T, Zufall F (1995) Block of cyclic nucleotide-gated channels in salamander olfactory receptor neurons by the guanylyl cyclase inhibitor LY 83583. J Neurophysiol 74: 2759–2762Google Scholar
  9. Liebowitz SM, Lombardini JB, Allen C (1989) Sulfone analogues of taurine as modifiers of calcium uptake and protein phosphorylation in rat retina. Biochem Pharmacol 38: 399–406Google Scholar
  10. Lombardini JB (1983) Effects of ATP and taurine on calcium uptake by membrane preparations of the rat retina. J Neurochem 40: 402–406Google Scholar
  11. Lombardini JB (1991) Taurine: retinal function. Brain Res Rev 16: 151–169Google Scholar
  12. López-Colomé AM, Pasantes-Morales H (1981) Effect of taurine on 45 Ca transport in frog retinal rod outer segments. Exp Eye Res 32: 771–780Google Scholar
  13. Militante JD, Lombardini JB (1998) The effect of chelerythrine inhibition of calcium uptake and ATPase activity in the rat retina. Biochem Pharmacol 55: 557–565Google Scholar
  14. Pasantes-Morales H, Ordóñez A (1982) Taurine activation of a bicarbonate-dependent, ATP-supported calcium uptake in frog rod outer segments. Neurochem Res 7: 317–328Google Scholar
  15. Pugh EN Jr, Lamb TD (1990) Cyclic GMP and calcium: the internal messengers of excitation and adaptation in vertebrate photoreceptors. Vision Res 30: 1923–1948Google Scholar
  16. Wei J-Y, Cohen ED, Tan Y-Y, Genieser H-G, Barnstable CJ (1996) Identification of competitive antagonists of the rod photoreceptor cGMP-gated cation channel:β-phenyl-1, N2-etheno-substituted cGMP analogues as probes of the cGMP-binding site. Biochem 35: 16815–16823Google Scholar

Copyright information

© Springer-Verlag 1998

Authors and Affiliations

  • J. D. Militante
    • 2
  • J. B. Lombardini
    • 2
    • 1
  1. 1.Ophthalmology & Visual SciencesTexas Tech University Health Sciences CenterLubbockUSA
  2. 2.Department of PharmacologyTexas Tech University Health Sciences CenterLubbockUSA

Personalised recommendations