The experiments described in this paper show that the isolated rod outer segment recorded in whole-cell is an ideal preparation to study in situ the guanosine 3':5'-cyclic monophosphate (cGMP) gated channels, the enzymes involved in phototransduction and the Na+-Ca2+,K+ exchanger. In particular, the role on phototransduction of intracellular Ca2+, Ca2+i, and the existence of possible modulation of Ca2+ movements across the plasma membrane were analyzed. It was found that the reduction of [Ca2+]i stimulates the GC without affecting the basal PDE activity: this regulation plays a key role in shaping the photoresponse kinetics and the low frequency noise of dark current. The Ca2+i homeostasis is entirely controlled by the exchangers, which Ca2+ extrusion rate was found to be driven exclusively by the electrochemical gradients of the cotransported ions, and by the Ca2+ entry through the cGMP gated channels, which were found to be modulated by nucleotide triphosphates.
cGMP channel, exchanger and phototransduction in isolated rod outer segments.
RISPOLI, Giorgio;
1997
Abstract
The experiments described in this paper show that the isolated rod outer segment recorded in whole-cell is an ideal preparation to study in situ the guanosine 3':5'-cyclic monophosphate (cGMP) gated channels, the enzymes involved in phototransduction and the Na+-Ca2+,K+ exchanger. In particular, the role on phototransduction of intracellular Ca2+, Ca2+i, and the existence of possible modulation of Ca2+ movements across the plasma membrane were analyzed. It was found that the reduction of [Ca2+]i stimulates the GC without affecting the basal PDE activity: this regulation plays a key role in shaping the photoresponse kinetics and the low frequency noise of dark current. The Ca2+i homeostasis is entirely controlled by the exchangers, which Ca2+ extrusion rate was found to be driven exclusively by the electrochemical gradients of the cotransported ions, and by the Ca2+ entry through the cGMP gated channels, which were found to be modulated by nucleotide triphosphates.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
