Ultracytochemical localization of Ca++-ATPase activity in the paraphyseal epithelial cells of the frog, Rana esculenta

Abstract

Ca++-ATPase activity was studied ultracytochemically (cf. Ando et al. 1981) in the paraphysis cerebri of the frog. An intense reaction was demonstrated on the plasmalemma of the microvilli at the apical pole of paraphyseal cells; in contrast, the basolateral plasmalemma showed only a slight staining. In addition, mitochondria, gap junctions, cilia, and cytoplasmic elements (e.g., microfilaments) displayed Ca++-ATPase activity. Variation of the Ca++-concentration in the incubation medium from 0.1 mM to 100 mM altered the Ca++-ATPase activity of the cell organelles. The substitution of Ca- by Mg-ions resulted in a conspicuous decrease in the enzyme activity, especially on the apical plasmalemma. Ca++-ATPase activity is claimed to be involved in a number of extra- and intracellular functions. In comparison to the epithelium of the adjacent choroid plexus the paraphyseal epithelial cell is thought to be a principal Ca-ion regulator of the cerebrospinal fluid in frogs.

Calcium-activated adenosine triphosphatase and gap junctions in rat epidermis.

“…Ca++-ATPase activity, an energy dependent calcium extrusion pump, is well accepted to reflect intracellular calcium level. Some cytochemical investigations of the Ca++-ATPase in several organs have been reported with a new one-step method by Ando et al (1,2,9,10,23,28). In our present study with the use of this method the enzyme activity in the rat epidermis was detected.…”

Ultracytochemical localization of Ca++-ATPase activity in the epithelial cells of guinea pig ciliary body.

“…By cytochemical means, the mitochondrial localization of Ca++-ATPase activity has been also reported to hold true for other tissues, e.g., heart muscle (1, 11), gastroliths (19), retinal photoreceptors (38,40), and paraphyseal epithelium (39), that is, tissues which were thought to transport Ca++ actively. Hence, in the ciliary epithelium, the role of mitochondria for Ca++ regulator could not be ignored and both the plasmalemma-bound Ca++-ATPase and the mitochondrial ATPase may contribute significantly to the transport of Ca++ as mentioned before.…”

“…In contrast, the optimal concentration of Mg++ for the activation of mitochondrial ATPase varied among the following tissues : 0.1 mM in heart muscle (11) and fish gastroliths (19) but 10 mM in the inner segments of retinal photoreceptors (40) . No activation occurs in the mitochondria of the paraphyseal epithelium of the frog (39) . In our study, the mitochondrial ATPase in ciliary epithelium was activated by 10 mM Mg++.…”

“…Ca++-ATPase activity investigated in various organs has been classified into two different types; 1) ATPase activated by Ca++ in the presence of Mg++ (14), and 2) ATPase activated only by Ca++ and inhibited in the presence of Mg++ (15,27,39). Our results show that the plasmalemma-bound Ca++_ ATPase activity of the nonpigment epithelium resembles the ATPase of the latter type, since this enzyme was activated by Ca++ in the absence of Mg++, but its activity was reduced in the presence of Mg++ with or without Ca++.…”

Ultrastructure and Ca++-ATPase activity of gap junctions under cryo-electron microscopic observation.

“…On the other hand, from the viewpoint of enzyme cytochemistry, three enzymes (Ca+ + -ATPase, adenylate cyclase and guanylate cyclase) activities have been demonstrated in the gap junction of various tissues (8,9,20,31,34). Interestingly, Fujimoto, et al (7) detected a different localization of reaction products of adenylate cyclase on isolated heart gap junctions between fixed and unfixed samples, implying that the localization of enzyme activity may alter under sample conditions.…”