Ca
++-activated adenosine triphosphatase (Ca
++-ATPase) activity in the epithelial cells of guinea pig ciliary body was demonstrated histo- and cytochemically with the use of a newly developed method (Ando
et al., 1981).
In nonpigment ciliary epithelial cells fixed for 60min in paraformaldehyde, intense reaction was observed on basolateral plasmalemma and mitochondria. In contrast, an intense reaction was localized only on mitochondria and gap junctions but not on the plasmalemma in the pigment epithelial cells. From the controls, this reaction was completely Ca
++- and ATP-dependent. The activity in fixed tissue with a mixture of paraformaldehyde and glutaraldehyde still remained moderately on the plasmalemma, but was completely abolished on mitochondria and gap junctions. The activity in the tissue after incubation in the medium with 2mM or 3mM Ca
++ concentration remained on the plasmalemma but almost disappeared from the mitochondria and gap junctions. Utilization of 1mM or lower Ca
++ concentration failed to show enzyme activity. When tissue was incubated in the medium containing both 5 or 10mM Ca
++ and Mg
++, the reaction products on the mitochondria were still intense. However, the activity on the plasmalemma was markedly weakened. When Mg
++ were used instead of Ca
++, a distinct reaction was also found on mitochondria, but not on the plasmalemma.
Our results clearly revealed that Ca
++-ATPase activity was localized on the plasmalemma, mitochondria and gap junctions in the ciliary epithelium. It is noteworthy that a much more intense reaction existed on the basolateral plasmalemma which has been suggested to play an important role for aqueous humour secretion facing the posterior chamber in the nonpigment epithelium.
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