ATPase activities of human retina and pigment epithelium-choroid

The Mg2+-, the Na+-K+-, and the HCO3--stimulated ATPase activities have been measured in the retina and pigment epithelium of postmortem human donor eyes. Activities were measured between 24 and 72 hr after death, following storage of the eyes in moistened chambers kept in a refrigerator. There appeared to be no significant differences in the ATPase activities between the 24 and 72 hr tissues. The human retina demonstrated both Mg2+- and Na+-K+-stimulated ATPase activity, but no HCO3+-stimulated ATPase activity, but not HCO3+-stimulated ATPase activity. The Na+-K+ ATPase activity was 1.54 mumol Pi/hr/mg protein, which amounted to 37% of the total ATP hydrolysis of the retina. The pigment epithelium-choroid showed significant Mg2+-, Na+-K+-, and HCO3--stimulated ATPase activities, with the stimulation caused by HCO3- about 25% greater than the effect due to Na+-K+, 0.64 vs. 0.51 mumol Pi/hr/mg protein. These findings in human retina and pigment epithelium-choroid show that certain metabolic processes continue to operate for several days after death.