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Transmission electron microscopy and ultracytochemistry were employed in an attempt to localize the enzyme calcium adenosine triphosphatase (Ca-ATPase) in the rod outer segments (ROS) of the toad retina. Utilizing a one-step incubation procedure, Ca-ATPase was identified as an electron-dense precipitate in the intradiskal spaces of the rod disks (vesicles) of the ROS. Analytical microscopy identified the reaction product as lead phosphate. The formation of the reaction product was dependent on the presence of ATP (the substrate) and calcium ions. However, calcium ions could be substituted for by magnesium ions. In addition, the reaction was vanadate sensitive. The latter is known to inhibit Ca-ATPase activity. Such data appear to indicate the presence of a Ca-Mg-ATPase in association with the rod disks. Since cyclic guanosine monophosphate (cyclic GMP), rather than calcium ions, is currently believed to be the primary intracellular messenger associated with phototransduction, the presence of an ROS Ca-ATPase may indicate other functions for this cation in the physiology and biochemistry of the visual process. Ca-ATPase might play a role in directional calcium fluxes between intracellular compartments.
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
January 1987,
The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
July 1978,
Biochemistry,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
January 1970,
Zeitschrift fur Zellforschung und mikroskopische Anatomie (Vienna, Austria : 1948),
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
November 1981,
Biochimica et biophysica acta,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
January 1986,
Comparative biochemistry and physiology. A, Comparative physiology,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
June 1987,
Experimental eye research,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
August 1967,
General and comparative endocrinology,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
October 1975,
Brain research,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
July 1966,
The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society,
W L Davis, and
H K Hagler, and
G R Farmer, and
J H Martin, and
G Bridges
February 1998,
Vision research,
