Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor

Coles, J. A. and Brown, J. E. (1976) Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor. Biochimica et Biophysica Acta: Biomembranes, 436(1), pp. 140-153. (doi: 10.1016/0005-2736(76)90226-1)

Abstract

Aspects of a possible involvement of hydrogen ions in the electrophysiological responses to light of Limulus ventral photoreceptors were investigated. A I M solution of either a zwitter-ionic pH buffer or a weakly-buffering control substance was pressure injected through a micropipette into a ventral photoreceptor cell. To estimate the amount injected, 35SO4 was included in the solution. Membrane currents induced by light flashes were measured by a voltage-clamp technique. The buffer-filled micropipette passed current and a 3 M KCl filled micropipette monitored membrane voltage. The sensitivity (peak light-induced current/stimulus energy) was measured, after dark adaptation, before and after injection. Injections of buffers, pH 6.3–7.2, to intracellular concentrations of at least 40–200 mM produced only a small mean decrease in sensitivity, approximately equal to that caused by injections of control substances. Excitation, therefore, apparently is not mediated by a change in intracellular pH. Buffers with pH values 5.4–8.4 were also injected. The time to peak of the response depended on pH, being shortened by up to 20% at pH values below 7.7 and lengthened at higher pH values. The time to peak of the response appeared to be shortened by an increase in intracellular pH-buffering capacity even when there was no change in intracellular pH.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Coles, Dr Jonathan
• Authors: Coles, J. A., and Brown, J. E.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Biochimica et Biophysica Acta: Biomembranes
• Publisher: Elsevier
• ISSN: 0005-2736
• ISSN (Online): 1879-2642