TY - JOUR
T1 - Ca2+ modulation of the cGMP‐gated channel of bullfrog retinal rod photoreceptors.
AU - Nakatani, K.
AU - Koutalos, Y.
AU - Yau, K. W.
PY - 1995/4/1
Y1 - 1995/4/1
N2 - 1. The outer segment of an isolated rod photoreceptor from the bullfrog retina was drawn into a pipette containing choline solution for recording membrane current. The rest of the cell was sheared off with a glass probe to allow internal dialysis of the outer segment with a bath potassium solution (‘truncated rod outer segment’ preparation). The potential between the inside and the outside of the pipette was held at 0 mV. 2. Application of bath cGMP, in the presence of 3‐isobutyl‐1‐methylxanthine (IBMX), gave rise to an outward membrane current. At saturating cGMP concentrations, this current was insensitive to intracellular Ca2+ at concentrations between 0 and 10 microM. At subsaturating cGMP concentrations, however, this current was inhibited by intracellular Ca2+. This sensitivity to Ca2+ declined after dialysis with a low‐Ca2+ solution, suggesting the involvement of a soluble factor. 3. At low (nominally 0) Ca2+, the half‐maximal activation constant and Hill coefficient for the activation of the cGMP‐gated current by cGMP were 27 microM and 2.0, respectively. At high (ca 10 microM) Ca2+, the corresponding values were 40 microM cGMP and 2.4. 4. The inhibition of the current by Ca2+ was characterized at 20 microM cGMP. Ca2+ inhibited the current by up to 60%, with half‐maximal inhibition at 48 nM Ca2+ and a Hill coefficient of 1.6.
AB - 1. The outer segment of an isolated rod photoreceptor from the bullfrog retina was drawn into a pipette containing choline solution for recording membrane current. The rest of the cell was sheared off with a glass probe to allow internal dialysis of the outer segment with a bath potassium solution (‘truncated rod outer segment’ preparation). The potential between the inside and the outside of the pipette was held at 0 mV. 2. Application of bath cGMP, in the presence of 3‐isobutyl‐1‐methylxanthine (IBMX), gave rise to an outward membrane current. At saturating cGMP concentrations, this current was insensitive to intracellular Ca2+ at concentrations between 0 and 10 microM. At subsaturating cGMP concentrations, however, this current was inhibited by intracellular Ca2+. This sensitivity to Ca2+ declined after dialysis with a low‐Ca2+ solution, suggesting the involvement of a soluble factor. 3. At low (nominally 0) Ca2+, the half‐maximal activation constant and Hill coefficient for the activation of the cGMP‐gated current by cGMP were 27 microM and 2.0, respectively. At high (ca 10 microM) Ca2+, the corresponding values were 40 microM cGMP and 2.4. 4. The inhibition of the current by Ca2+ was characterized at 20 microM cGMP. Ca2+ inhibited the current by up to 60%, with half‐maximal inhibition at 48 nM Ca2+ and a Hill coefficient of 1.6.
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U2 - 10.1113/jphysiol.1995.sp020648
DO - 10.1113/jphysiol.1995.sp020648
M3 - Article
C2 - 7541463
AN - SCOPUS:0028987906
SN - 0022-3751
VL - 484
SP - 69
EP - 76
JO - The Journal of physiology
JF - The Journal of physiology
IS - 1
ER -