Ultrastructural localization of carbonic anhydrase activity in the rat choroid plexus epithelial cell

Abstract

Localization of carbonic anhydrase activity was studied electron microscopically on cells of the rat choroid plexus epithelium. For the ultracytochemical detection of these activities, Yokota's technique (1969), which is the modification of Hansson's method (1967) was employed. Numerous electron dense reaction products were observed in the microvilli of the choroidal epithelial cell. The reaction deposits were also remarkably present in the infoldings of the basal plasmalemma but to a lesser extent than in the microvilli. The localization sites were mainly on the plasma membrane, but some reaction products were also observed in the cytoplasm near the plasma membrane. Hardly any reaction product was found in the intracellular organelles except for the mitochondria in which reaction products were occasionally observed on the cristae. These activities were completely inhibited by acetazolamide. As the carbonic anhydrase activity was histochemically seen in the microvilli and the basal infoldings, it is likely that carbonic anhydrase is related to an active transport process in the secretion of cerebrospinal fluid as is Na+, K+ -ATPase (Masuzawa et al. 1980).

Histochemistry and immunocytochemistry of the developing ependyma and choroid plexus

“…The adenosine precursor of ATP also is synthesized in the interstitium of the choroid plexus, although not in the epithelial cells (Braun et al, 1994). These enzymatic activities are thought to be important for the production and secretion of CSF; another enzyme believed to be essential in this regard, carbonic anhidrase, also is strongly demonstrated histochemically in choroid plexus epithelium (Becker and Sutton, 1975;Masuzawa et al, 1981;Masuzawa and Sato, 1983). These activities are shown in both fetal and mature cells of the choroid plexus.…”

“…Lysosomal enzymes such as acid and alkaline phosphatases are histochemically demonstrated in both fetal and adult choroid plexus epithelial cells (Becker and Sutton, 1975;Masuzawa et al, 1981;Masuzawa and Sato, 1983;Ziegels, 1975).…”

Carbonic Anhydrase and 2′3′ Cyclic Nucleotide 3′ Phosphohydrolase Activity in Perfused Rat Brain and Rat Brain Primary Culturesa

“…In the human retina, CA I1 is found in the Muller cells, which show some but not all of the characteristics of a s t r o c y t e~.~ CA I1 activity has also been detected in primary cultures from neonatal rodent brains.6 Immunocytochemistry of such cultures has shown intense staining of either onIy the presumptive oligodendrocytes that can occur in such cultures,' or an additional weaker staining of the predominant (GFAP+) astrocytes in these cultures. 8 In the present study we have correlated the occurrence of CA activity with 2'3' cyclic nucleotide 3' phosphohydrolase (2'3' CNP) activity, an oligodendrocyte and myelin marker:JO in both predominantly primary astrocyte cultures from neonatal rat cerebral hemispheres at varying times in culture and in the brains from perfused rats. All results are the averages of two separate determinations on same sample.…”