Implications of the immunohistochemical localization of the carbonic anhydrase isozymes for their function in normal and pathologic cells

Carbonic anhydrase II does not regulate nitrite-dependent nitric oxide formation and vasodilation

BACKGROUND AND PURPOSE

Although it has been reported that bovine carbonic anhydrase CAII is capable of generating NO from nitrite, the function and mechanism of CAII in nitrite-dependent NO formation and vascular responses remain controversial. We tested the hypothesis that CAII catalyses NO formation from nitrite and contributes to nitrite-dependent inhibition of platelet activation and vasodilation.

EXPERIMENT APPROACH

The role of CAII in enzymatic NO generation was investigated by measuring NO formation from the reaction of isolated human and bovine CAII with nitrite using NO photolysis-chemiluminescence. A CAII-deficient mouse model was used to determine the role of CAII in red blood cell mediated nitrite reduction and vasodilation.

KEY RESULTS

We found that the commercially available purified bovine CAII exhibited limited and non-enzymatic NO-generating reactivity in the presence of nitrite with or without addition of the CA inhibitor dorzolamide; the NO formation was eliminated with purification of the enzyme. There was no significant detectable NO production from the reaction of nitrite with recombinant human CAII. Using a CAII-deficient mouse model, there were no measurable changes in nitrite-dependent vasodilation in isolated aorta rings and in vivo in CAII^-/- , CAII^+/- , and wild-type mice. Moreover, deletion of the CAII gene in mice did not block nitrite reduction by red blood cells and the nitrite-NO-dependent inhibition of platelet activation.

CONCLUSION AND IMPLICATIONS

These studies suggest that human, bovine and mouse CAII are not responsible for nitrite-dependent NO formation in red blood cells, aorta, or the systemic circulation.

Immunohistolocalization and gene expression of secretory carbonic anhydrase isoenzyme CA-VI in canine nasal cavity

Immunolocalization of the secretory form of carbonic anhydrase isoenzyme, CA-VI were studied using a specific canine CA-VI antiserum, and CA-VI mRNA signals were also investigated using the reverse-transcriptase polymerase chain reaction (RT-PCR) in canine nasal mucosal epithelia and glands. Immunoreactivity to CA-VI was positive throughout the mucosal epithelial cells and in the cytoplasm of serous acinar and ductal epithelial cells of the nasal mucosa and glands, including the vestibule of the nose, but the mucous acinar cells of the glands were immunonegative. We detected CA-VI gene transcripts in the same regions as the CA-VI immunoreactivity. The physiological roles of CA-VI in the nasal mucosal epithelium and glands might maintain bicarbonate levels in nasal secretions and protect the mucosa against acid.

Antibodies to carbonic anhydrase in patients with connective tissue diseases: relationship with lung involvement

The aim of this study is to evaluate the presence of antibodies to carbonic anhydrase I and/or II (ACAI and ACAII) in patients affected by connective tissue diseases (CTD) and to investigate their association with lung involvement evaluated by High resolution CT scan (HRCT). Ninety-six patients affected by CTD were studied, i.e. 33 rheumatoid arthritis (RA), 8 psoriatic arthritis (PA), 8 ankylosing spondilitis (AS), 23 Systemic Lupus Erythematosus (SLE), 10 Sjogren Syndrome (SS), and 14 Systemic Sclerosis (SSc). ACA were detected by ELISA. The lung involvement was evaluated by means of a previously described HRCT score. According to a receiver operator characteristic curve, patients were divided into those with HRCT score > or = 10 and those with HRCT score < 10, where HRCT score > or = 10 was predictive of interstitial lung disease. ACAI and/or ACAII were detected in 30/96 patients (31.2%) (P < 0.0001 in comparison with controls). In particular, the prevalence of ACAI and/or ACAII was significantly higher in patients with RA (P = 0.002), PA (P < 0.0001), SLE (P = 0.0003) and SSc (P < 0.0001). A positive correlation was found between HRCT scores and CRP or ACAI levels (P = < 0.0001 and P = 0.004, respectively). Thirty-nine of 96 patients (40.6%) showed a HRCT score > or = 10 and both their CRP and ACAI levels were significantly higher when compared with patients showing a HRCT score less than 10 (P < 0.0006 and P = 0.0009, respectively). Moreover, C3 and C4 complement fractions inversely correlated with HRCT scores (P = 0.0004 and P < 0.0001, respectively) and lower values of C3 and C4 complement fractions were found in patients with HRCT score > or = 10 than in those with HRCT score less than 10 (P = 0.014 and P = 0.007, respectively). Due to the lower levels of complement fractions detected in patients with HRCT score > or = 10, a possible immune-complex-mediated pathogenic mechanism of lung involvement could be suggested.

Deficiencies of physiologic calcification inhibitors and low-grade inflammation in arterial calcification: lessons for cartilage calcification

Apart from clinical parallels, similarities in the pathogenesis of arterial and articular cartilage calcification have come to light in recent years. These include the roles of aging, of chronic low-grade inflammation and of genetic and acquired dysregulation of inorganic pyrophosphate (PP(i)) metabolism. This review focuses on recent developments in understanding the pathogenesis of artery calcification pertinent to interpretation of the mechanistic basis for articular cartilage calcification in aging and osteoarthritis.

Parallels between arterial and cartilage calcification: what understanding artery calcification can teach us about chondrocalcinosis

The pathogenesis of arterial calcification and chondrocalcinosis has become concurrently illuminated in recent years. For example, both processes occur in chronic inflammation-mediated degenerative diseases associated with aging (including atherosclerosis and osteoarthritis). Both processes are also modulated by altered gene expression by resident cells and by the release of mineralization-competent cell fragments (matrix vesicles and apoptotic bodies). Among the variety of genetic diseases associated with artery calcification are disorders that also promote cartilage calcification and/or dysregulated bone formation. Our discussion highlights that pathologic arterial and articular cartilage calcification both can be owing to genetic deficiencies of calcification inhibitors such as the inorganic pyrophosphate-generating ectoenzyme PC-1/nucleotide pyrophosphatase phosphodiesterase 1. Conversely, pathologic arterial and articular cartilage calcification also can primarily arise as a consequence of active processes driven by inflammatory cytokines and by disordered calcium and inorganic phosphate homeostasis. As discussed in this review, recent developments in the pathogenesis of arterial calcification provide valuable information pertinent to potential future advances in controlling chondrocalcinosis.

Cell biology of laryngeal epithelial defenses in health and disease: preliminary studies

Esophageal epithelium has intrinsic antireflux defenses, including carbonic anhydrases (CAs I to IV) that appear to be protective against gastric reflux. This study aimed to investigate the expression and distribution of CA isoenzymes in laryngeal epithelium. Laryngeal biopsy specimens collected from the vocal fold and interarytenoid regions were analyzed by Western blotting and immunofluorescence. Carbonic anhydrases I and II were expressed by the majority of samples analyzed. In contrast, CA III was differentially expressed in the interarytenoid samples and was not detected in any vocal fold samples. The expression of CA III was increased in esophagitis as compared to normal esophageal tissue. Carbonic anhydrase I and III isoenzymes were distributed cytoplasmically in the basal and lower prickle cell layers. The laryngeal epithelium expresses some CA isoenzymes and has the potential to protect itself against laryngopharyngeal reflux. Laryngeal tissue may be more sensitive to injury due to reflux damage than the esophageal mucosa because of different responses of CA isoenzymes.

Potassium recycling pathways in the human cochlea

OBJECTIVES/HYPOTHESIS

Potential pathways for recycling potassium (K+) used in the maintenance of inner ear electrochemical gradients have been elucidated in animal models. However, little is known about K+ transport in the human cochlea. This study was designed to characterize putative K+ recycling pathways in the human ear and to determine whether observations from animal models can be extrapolated to humans.

STUDY DESIGN

A prospective laboratory study using an immunohistochemical approach to analyze the distribution of key ion transport mediators in the human cochlea.

METHODS

Human temporal bones were fixed in situ within 1 to 6 hours of death and subsequently harvested at autopsy. Decalcification was accomplished with the aid of microwaving. Immunohistochemical staining was then performed to define the presence and cell type-specific distribution of Na,K-ATPase, sodium-potassium-chloride cotransporter (NKCC), and carbonic anhydrase (CA) in the inner ear.

RESULTS

Staining patterns visualized in the human cochlea closely paralleled those seen in other species. Anti-Na,K-ATPase stained strongly the basolateral plasma membrane of strial marginal cells and nerve endings underlying hair cells. This antibody also localized Na,K-ATPase to type II, type IV, and type V fibrocytes in the spiral ligament and in limbal fibrocytes. NKCC was present in the basolateral membrane of strial marginal cells as well as in type II, type V, and limbal fibrocytes. Immunoreactive carbonic anhydrase was present in type I and type III fibrocytes and in epithelial cells lining Reissner's membrane and the spiral prominence.

CONCLUSIONS

The distribution of several major ion transport proteins in the human cochlea is similar but not identical to that described in various rodent models. These results support the presence of a complex system for recycling and regulating K+ homeostasis in the human cochlea, similar to that described in other mammalian species.

Immunohistochemical localization of carbonic anhydrases I, II, and VI in the developing rat sublingual and submandibular glands

Carbonic anhydrase has been localized to the acini and ducts of mature rat salivary glands. This enzyme has been associated with ion transport, a prominent function of striated and excretory ducts in salivary glands, suggesting that it might be used as a marker of ductal differentiation. The purpose of this study was to immunohistochemically document developmental changes in carbonic anhydrase in the ducts of the rat sublingual and submandibular glands. Immunohistochemistry was performed with antibodies to human carbonic anhydrase isoenzymes I, II and VI on sections of sublingual and submandibular glands from rats at representative postnatal developmental ages. Reactions were weak in the ducts of both glands at 1 day, then progressively increased. By 42 days, reactions had the adult pattern of virtually none in the mucous or seromucous acini, moderate to strong in the striated and excretory ducts, and none to weak in the intercalated ducts. Weak to moderate reactions were observed in the granular convoluted tubules of the submandibular gland as they became recognizable at age 42 days. Reactions to carbonic anhydrase I and II antibodies also increased from none (1 day) to modest (42 days) in the demilunes of the sublingual gland. The order of reaction intensity of the antibodies was II > I > VI. When localized via these anti-human antibodies, carbonic anhydrase is a useful marker of the functional differentiation of the striated and excretory ducts of the developing rat sublingual and submandibular glands.

Localization of carbonic anhydrase in guinea pig Bowman's glands

We examined the histochemical localization of carbonic anhydrase (CA) in Bowman's glands by light and electron microscopy. Neither CAI nor CAII was detected immunohistochemically in the duct cells. However, by enzyme histochemistry the duct cells revealed electron-dense precipitates demonstrative of CA in the microvilli and intercellular digitations. The reaction product was also noted in small vesicles in the cytoplasm of duct cells. In cells of the acini, the well-developed short microvilli, basolateral cell membrane, and mitochondria along the basolateral membrane showed strong deposits indicating CA activity. Dense reaction product of CA was also detected in a small core within the electron-lucent granules of the secretory cells, although CAI and CAII were not detected by immunostaining in the secretory granules. Although the functional significance of CA in Bowman's glands is obscure, the enzyme may play a role in regulation of pH and ion balance in the mucous layer covering the olfactory epithelium. The presence of CA activity in the ducts suggests that these structures are not simple tubes serving as a conduit for secretory substances but participate in modifying the luminal content by secreting CA. (J Histochem Cytochem 47:1525-1531, 1999)

Enzyme histochemical and immunohistochemical localization of carbonic anhydrase as a marker of ductal differentiation in the developing rat parotid gland

BACKGROUND

Carbonic anhydrase has been localized to the acini and ducts of mature rat parotid glands. This enzyme has been associated with ion transport, a prominent function of striated and excretory ducts in salivary glands, suggesting that it might be used as a marker of ductal differentiation. The purpose of this study was histochemically to document developmental changes in carbonic anhydrase in the ducts of the rat parotid gland.

METHODS

Parotid glands were excised from rats at representative developmental ages. Enzyme histochemistry was done on frozen sections fixed in acetone, and immunohistochemistry was performed with antibodies to human carbonic anhydrase isoenzymes I, II, and VI on paraffin sections of glands fixed in Helly's fluid.

RESULTS

Carbonic anhydrase activity was weak until age 21 days after birth, when it had increased slightly in the acini and intercalated ducts and moderately in striated and excretory ducts. The adult pattern was attained by 28 days, in which reactions were moderate to strong in the striated and excretory ducts and modest in the acini and intercalated ducts. Immunohistochemical reactions were weak until 14 days, then increased rapidly, and by 28 days approached the adult pattern of virtually none in the acini and modest to moderately strong in the striated and excretory ducts. The order of reaction intensity of the antibodies was II > I > VI.

CONCLUSIONS

Carbonic anhydrase is a useful marker of the functional differentiation of the striated and excretory ducts of the developing rat parotid gland.

CD4-positive T-lymphocytes infiltrate the bronchial mucosa of patients with Sjögren's syndrome

To investigate the degree and the type of inflammation in the bronchial mucosa in patients with Sjögren's syndrome, we examined lobar bronchial biopsies obtained from 10 patients with Sjögren's syndrome (six with primary and four with secondary) and eight control subjects. Histochemistry with hematoxylin-eosin was performed both to identify the number of mononuclear cells and eosinophils and to measure the thickness of the basement membrane. Immunohistochemistry was performed to identify neutrophils (neutrophil-elastase), macrophages (CD68), and T-lymphocyte subpopulations (CD4 and CD8) in the submucosa. Subjects with Sjögren's syndrome presented a greater number of CD4-positive T-lymphocytes than did the normal control subjects (p = 0.0129). Instead, eosinophils, neutrophils, macrophages, CD8 positive T-lymphocytes, and basement membrane thickness were similar in the two groups. There were no differences in cell counts between patients with primary and those with secondary Sjögren's syndrome and between symptomatic and asymptomatic patients. No correlation was found between cell counts, symptoms, lung volumes, and disease duration. This study has shown that patients with Sjögren's syndrome have an increased number of CD4 positive T-lymphocytes in the bronchial mucosa outside of the bronchial glands, supporting the concept that, in the airways. Sjögren's syndrome involves also extraglandular tissues.

Antibodies to carbonic anhydrase in patients with immune cholangiopathies

BACKGROUND/AIMS

Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have been described in autoimmune disorders. Serum from patients with immune-mediated liver diseases was studied to determine whether antibodies to carbonic anhydrase II and/or pyruvate dehydrogenase could distinguish autoimmune cholangitis as immunologically distinct from primary biliary cirrhosis.

METHODS

Antibody assays to carbonic anhydrase II (Western blot) and pyruvate dehydrogenase (flow cytometry) were performed on the sera of patients with autoimmune cholangitis (6), primary biliary cirrhosis (12), primary sclerosing cholangitis (12), autoimmune hepatitis (12), and control (Gilbert syndrome; 8).

RESULTS

Reactivity to carbonic anhydrase II was detected in 5 of 6 patients with autoimmune cholangitis, 1 of 12 patients with primary biliary cirrhosis, 1 of 12 patients with autoimmune hepatitis, and no other patients. Individuals with autoimmune cholangitis were more likely than the other patients to be reactive to carbonic anhydrase II (P < 0.001). Patients with primary biliary cirrhosis were more reactive to pyruvate dehydrogenase compared with all other groups (P < 0.001).

CONCLUSIONS

An antibody to human carbonic anhydrase II is frequently detected in the sera of patients with autoimmune cholangitis and is uncommon or not present in other cholangiopathies. These data provide evidence that autoimmune cholangitis and primary biliary cirrhosis represent distinct entities with unique patterns of immunoreactivity.

Carbonic anhydrase type II in regenerating retinal pigment epithelium. A histochemical study in the rabbit

Type II carbonic anhydrase (CAII) in the cytoplasm of the retinal pigment epithelium (RPE) may contribute to the transport of water and solutes across the RPE. The activity of this enzyme in RPE during its response to damage, e.g., during regeneration, is therefore of interest in understanding retinal disease. Immuno-histochemistry was used to compare CAII activity of normal RPE and RPE experimentally induced to regenerate. In normal rabbits, the RPE stained intensely with a peroxidase-linked antibody specific for human CAII. Regenerating RPE stained less intensely. Within the regenerating epithelium, staining appeared more intense in mature cells than in immature ones, suggesting that CAII activity gradually returns during RPE regeneration.

The significance of carbonic anhydrase expression in human colorectal cancer

BACKGROUND

Carbonic anhydrase isoenzymes I and II are present in normal colorectal mucosa. This study aimed to determine if carbonic anhydrase is present in colorectal cancer and what is its potential clinical significance.

METHODS

The messenger RNA (mRNA) and protein expression of carbonic anhydrase isoenzyme I were analyzed in fresh specimens of colorectal adenocarcinoma by Northern and Western blots, respectively. The immunohistochemical expression was subsequently studied in a larger number of formalin-fixed surgical specimens.

RESULTS

All of 30 normal colon samples had a strong RNA hybridization signal. Only 4 of 39 paired colorectal cancer and none of 9 normal liver samples had detectable levels of carbonic anhydrase mRNA. Isoenzyme I protein expression showed similar results. In a separate group of patients, immunohistochemical studies showed that 16 of 96 colorectal tumors had positive staining cells. All positive tumors were well or moderately differentiated carcinomas (P < 0.05). When analyzed retrospectively, immunoreactive cases were more likely to be in a group with a good outcome (P < 0.01) and to lack vascular invasion (P < 0.01) than negative cases.

CONCLUSIONS

The majority of colorectal cancers do not express carbonic anhydrase isoenzyme I. The presence of any isoenzyme I-positive immunoreactive cancer cells may be associated with a more favorable outcome in colorectal cancer.

Comparative immunohistolocalization of carbonic anhydrase isozymes I, II and III in the equine and bovine digestive tract

Immunohistochemical localizations of carbonic anhydrase isozymes (CA-I, CA-II and CA-III) in equine and bovine digestive tracts were studied. In the horse, epithelial cells in both the oesophagus and non-glandular part of the stomach lacked all three isozymes. In contrast, surface epithelial and parietal cells in the glandular region of the stomach showed reactivity for CA-II. In the small intestine, absorptive columnar cells covering the villi in the duodenum were positive for CA-II. The epithelium of the jejunum and ileum lacked all three isozymes. In the large intestine, CA-II was detected in the columnar cells in the upper part of the crypt. In cattle, epithelial cells of the oesophagus showed reactions for CA-I and CA-III but not for CA-II. Although the absorptive epithelial cells of the small intestine lacked CA-I, CA-II and CA-III, those of the upper part of large intestine crypts were heavily stained for all three isozymes.

Differentiation of inner ear fibrocytes according to their ion transport related activity

Fibrocytes in the lateral wall and limbus of the gerbil cochlea evidenced a capacity for ion transport activity by immunostaining for transport mediating enzymes including Na,K-ATPase, carbonic anhydrase (CA) and creatine kinase (CK). Fibrocytes of the spiral ligament unlike those in the suprastrial region and limbus decreased in abundance from base to apex. Spiral ligament fibrocytes at a given position along the cochlea varied in content of transport related enzymes, and on the basis of immunostaining, location and orientation, were classified into four types. Type I fibrocytes under the stria vascularis stained for CA isozymes II and III and CK isozyme BB. Type II fibrocytes under the outer sulcus and spiral prominence epithelium were found to contain only Na,K-ATPase. Type III fibrocytes lying adjacent to bone in the inferior region of the spiral ligament contained CA II and III and CK isozymes BB and MM. Type IV fibrocytes located more superficially in the inferior part of the spiral ligament stained variably for all the enzymes. Superficial fibrocytes in the suprastrial area disclosed Na,K-ATPase whereas the underlying fibrocytes stained for CA and CK. Limbal fibrocytes reacted with antisera to all the enzymes except CA III. Most fibrocytes in stromal plates beneath the vestibular system's neurosensory epithelium contained Na,K-ATPase and CA II but not CA III. These findings point to cooperativity in fluid and ion transport between epithelial cells and neighboring fibrocytes and demonstrate functional diversity of fibrocytes of the inner ear providing a basis for classifying those in the spiral ligament.

Ultrastructural study of cytochemical localization of carbonic anhydrase in the inner ear

Vibratome sections were stained for cytochemical localization of carbonic anhydrase (CA) activity in vestibular neuro-epithelium, spiral ligament and spiral limbus. The new finding is the localization of reaction products in the interdental cells of the spiral limbus, Claudius' cells, mesothelial cells of the lower border of spiral ligament, vestibular sensory cells and perilymphatic cells, which have not earlier been proved to have CA activity. The interdental cells showed the products only on the basolateral infoldings. Claudius' cells showed prominent products in the microvilli. In the vestibular sensory cells, the products were present only in the stereocilia and cuticular areas. The perilymphatic fibrocytes under the vestibular sensory epithelium, like the fibrocytes of the spiral ligament, revealed diffuse products throughout the whole cell. In the vestibular supporting cells and transitional cells, the reaction products were localized diffusely in the cytosol, but not in the secretory granules. In the long cell projections of the transitional cells, type II fibrocytes at spiral prominence, mesothelial cells at the uppermost region of the spiral ligament and Borghesan's zone, the localization of the reaction products was the same as that of the basolateral infoldings of the vestibular dark cells and marginal cells of stria vascularis shown previously.

Carbonic anhydrase III in the salivary glands and kidney of the Japanese monkey (Macaca fuscata)

Carbonic anhydrase III (CA-III) was found in muscles of the Japanese monkey by the double immunodiffusion test and western blotting using antiserum raised against equine CA-III. Immunocytochemical localization of CA-III in the salivary glands and kidney of the monkey was studied using an avidin-biotinylated glucose oxidase complex. CA-III was found mainly in the striated duct and interlobular duct cells of the parotid glands. In the submandibular glands, striated duct, interlobular duct, and excretory duct cells were strongly stained for CA-III. In the kidney of the monkey, CA-III was localized mainly in the dark cells of the collecting duct at the medulla and in the epithelial cells of thick limb of Henle's loop.

Comparative distribution of carbonic anhydrase isozymes III and II in rodent tissues

Carbonic anhydrase (CA) III was demonstrated immunocytochemically in epithelium in some regions of salivary gland ducts, colon, bronchi, and male genital tract and in adipocytes, in addition to skeletal muscle and liver where the isozyme was previously localized. Basal cells beneath the submandibular gland's excretory ducts in guinea pig stained for CA III. Carbonic anhydrase III occurred alone in some and with CA II in other sites but was often absent from CA-II-containing types of cells. This was exemplified by CA III's abundance in CA-II-positive proximal colon and its sparsity in the CA-II-rich distal colon of the mouse. Striated ducts in guinea pig, but not mouse salivary glands, stained darker for CA and appeared accordingly to function more actively in ion transport compared with excretory ducts. Carbonic anhydrase content varied among genera in liver and pancreas and between mouse species and strains in salivary glands and kidney. Newly observed murine sites of CA II activity included Auerbach's plexus and a population of leukocytes infiltrating the lamina propria in small intestine, and several types of cells in the male genital tract. In immunoblot tests, antisera to CA III showed no cross reactivity with antisera to CA II, but those to CA II disclosed weak cross reactivity with CA III.

Immunolocalization of Na+,K(+)-ATPase and carbonic anhydrase in the gerbil's vestibular system

The distribution of two ion transport enzymes in the vestibular system was investigated immunocytochemically. Immunostaining demonstrated abundant Na+,K(+)-ATPase in the basolateral plasmalemma of all dark cells and of cuboidal (transitional) cells bordering maculae and planum semilunatum cells bordering cristae. Na+,K(+)-ATPase was also present in nerve terminals impinging on vestibular hair cells and around nerve fibers and ganglion cells. Na+,K(+)-ATPase containing cells with fine intertwining processes were found within the perilymphatic stroma beneath maculae and cristae. These cells and interspersed nerves form a distinct, highly cellular plate that lies under neurosensory epithelium selectively. The catalytic alpha subunit of Na+,K(+)-ATPase in vestibular epithelia differs antigenically from the alpha subunit in nerves and from the alpha subunit in salivary gland and renal epithelium. Carbonic anhydrase (CA) isozyme II was localized in the apex of all supporting cells in neurosensory epithelia. In contrast, CA II immunostaining varied in vestibular dark cells showing heterogeneity in ion transport activity among these cells. Immunostaining evidenced CA II also in perilymphatic stromal cells which were presumably fibroblastic in nature and which correspond in location with the Na+,K(+)-ATPase positive cells under the vestibular neurosensory epithelium.

Ultrastructural localization of carbonic anhydrase in the vestibular end organs of the guinea pig

Carbonic anhydrase activity was demonstrated cytochemically on an ultrastructural level in the vestibular end organs of the guinea pig. Reaction product was found in the dark cells, transitional cells, cells of the planum semilunatum and supporting cells. In the dark cells, reaction product was observed in the cytoplasm as well as in the basal infoldings. Reaction product was also observed in the basal infoldings of the transitional cells and the cells of the planum semilunatum. The globular structures inside the supporting cells, transitional cells and the cells of the planum semilunatum were also surrounded by the reaction product. These findings suggest that carbonic anhydrase may have different functions, such as water and ion transport, respiration, nutrition and calcium carbonate deposition in the vestibular end organs.

Selenium-induced autometallographic demonstration of endogenous zinc in organs of the rainbow trout, Salmo gairdneri

Autometallographic (AMG) silver enhancement of endogenous zinc was studied in seven organs of the rainbow trout Salmo gairdneri. Groups of trout were injected intraperitoneally with sodium selenite in doses ranging from 0.08 to 25 ppm, administered 1 h before being killed. The concentration of selenium obtained by each organ was determined by gamma-spectrometry, and compared with the autometallographic deposition of silver grains. The relative accumulation of selenium in the organs was: liver greater than spleen greater than kidney greater than intestine greater than gills greater than brain greater than muscle. In the fish labelled with 10 and 25 ppm Se, AMG-deposits were found (1) within lysosomes of liver cells, (2) within the granules and on the nuclear membrane of melanophores in the spleen, (3) on the microvilli and in the apical cytoplasm of renal proximal tubular cells, (4) within the granules and along the plasma membrane of intestinal eosinophilic granule cells, and in the apical portion of the intestinal epithelium, and (5) in the gills, within granule cells and on the surface of the ionocytes. In the trouts injected with 5 ppm Se, silver grains were still observed in the liver, the intestine, and the gills, whereas, no such grains were found in preparations from fish having received 1 ppm Se. The use of selenium for the histochemical demonstration of endogenous zinc versus exogenous metals is discussed. Also, consideration is given to the question of which part of the total tissue zinc that is histochemically reactive.

Heterogeneity of apical glycoconjugates in kidney collecting ducts: further studies using simultaneous detection of lectin binding sites and immunocytochemical detection of key transport enzymes

In the search for a functional role for the polarized glycoconjugates of rat collecting duct epithelial cells, the relation between binding of various lectins and expression of cellular transport enzyme profile of the cells was studied. For this purpose, principal and intercalated cells of rat kidney collecting duct were identified by morphological criteria and by their immunocytochemically determined content of (Na+ + K+)-ATPase and carbonic anhydrase (CA II), respectively. Various N-acetylgalactosamine-specific lectins such as those from Helix pomatia and Maclura pomifera revealed heterogeneity among both principal and intercalated cells, whereas alpha-N-acetylgalactosamine-specific lectin from Dolichos biflorus and Vicia villosa bound preferentially to principal cells. Still another lectin from Arachis hypogaea reacted with most collecting duct cells in the cortex and outer medulla, but only with a subpopulation of cells in the inner medulla. Interestingly, some lectins reacted exclusively with the apical aspect of the collecting duct epithelial cells, whereas others revealed both an apical and basolateral distribution of lectin reactive glycoconjugates. The results thus show subtle differences in the glycocalyx structure of principal and intercalated cells and differences in the intracellular polarization of glycoconjugates of these cells. Thus, lectins may be useful tools in the study of the molecular mechanisms which establish and maintain the polarized functions of principal and intercalated cells.

Ultrastructural and immunohistochemical characterization of submandibular duct cells in culture and modification of outgrowth differentiation by manipulation of calcium ion concentration

The recognized need for epithelial cell culture models for cystic fibrosis (CF) research has resulted in ongoing efforts to improve normal and CF submandibular duct cell culture capabilities. The duct is most likely the site of the CF defect in this and other exocrine glands. In a previous report conditions required for the successful primary explant culture of normal and CF submandibular glands were outlined; however, terminal keratinization and involution of these cultures were recognized as severe limiting factors to their utilization in CF research. This report explores the effects of calcium concentrations in the medium, growth factor supplements, and matrix components on growth and differentiation of these cultures. Results of the study further confirm the ductal origin of cells in the outgrowth and demonstrate that progressive keratinization is initiated only after cells proliferate beyond the environment of the explant fragment. Keratinization with subsequent multilayering, desmosome formation, and involution in the cell outgrowth are governed in degree by the calcium concentration of the growth medium. Upon reduction of medium calcium to 0.1 mM concentration, the cells proliferate as a monolayer and subculture through 8 to 9 passages and retain the capacity to undergo ductlike differentiation.

Lectin binding on carbohydrate compounds of the flask cells in the claw-frog kidney

The carbohydrate compounds of the mucus of flask cells in the kidney of claw-frogs (Xenopus laevis) were analysed through lectin binding studies. After removing epoxy resin semithin sections were incubated with 7 lectins (WGA, RCA I, PNA, LCH, UEA, LPA) marked by horseradish peroxidase and 2 unmarked lectins (VAA, Con A). The glycosaminoglycans in the canalicular lumen of flask cells showed a strong reaction with WGA and RCA, whereas the binding of PHA, Con A, and LCH was weaker. No reaction was observed with PNA, UEA, LPA, and VAA. The mucus of the flask cells seems to be rich in N-acetyl-glycosamine and -galactosamine. It contains also mannose, glucose, and galactose, but seems to have no fucose or N-acetyl-sialic acid residues.

Omeprazole, a specific inhibitor of H+-K+-ATPase, inhibits bone resorption in vitro

Omeprazole has been previously shown to block gastric acid secretion by specific inhibition of gastric parietal cell membrane H+-K+-ATPase. It is now demonstrated that similar concentrations of omeprazole will inhibit PGE2- and PTH-stimulated 45Ca++ release from prelabelled neonatal mouse calvariae without affecting the viability of cultured calvaria explants.

Heterogeneous distribution of glycoconjugates in human kidney tubules

Paraffin sections of normal human kidney were stained with a battery of ten lectin-horseradish peroxidase conjugates. Staining of proximal tubules revealed a relatively uniform distribution of glycoconjugates having bi- and/or triantennary N-linked sugar chains as well as terminal beta-galactose and alpha-fucose in all cells. In contrast, terminal alpha- and beta-galactose and alpha-fucose were localized in only some cells of the thin limbs, whereas N-linked sugar chains and terminal alpha-N-acetylgalactosamine occurred in all cells. In the ascending thick limbs, terminal alpha-N-acetylgalactosamine was found in some cells and N-linked sugar chains and terminal beta-galactose were present in all cells. The distal convoluted tubules contained N-linked oligosaccharides and terminal beta-galactose in all cells. Terminal alpha-N-acetylgalactosamine was found in some but not all profiles of distal convoluted tubules in a few kidneys. In the initial (connecting) segment of cortical collecting ducts, cells varied in their content of glycogen and glycoconjugates with terminal alpha- and beta-galactose, alpha-fucose and alpha-N-acetylgalactosamine, but cells in this segment evidenced uniform localization of N-linked sugar chains. A similar distribution of sugars occurred in the medullary ray segment of cortical collecting ducts, except for terminal beta-galactose which was present in all cells. In the medullary collecting ducts, there was also considerable cell-to-cell variation in the content and distribution of glycogen and glycoconjugates having N-linked sugar chains, terminal alpha-galactose, alpha-fucose, alpha-N-acetylgalactosamine, and the disaccharide galactose-(beta 1----3)-N-acetylgalactosamine. The content and distribution of glycoconjugates in the nephron varied only slightly between kidneys from different individuals, but individual variability was extensive in the collecting ducts. The reasons for these individual differences have not been determined, however. Cellular heterogeneity of glycosubstances within the different regions of the human kidney correlates with similar findings in other mammals and implies diverse functional roles for the various types of complex carbohydrates in the kidney.

The value of inherited deficiencies of human carbonic anhydrase isozymes in understanding their cellular roles

Very little light has been shed on the role of the low-activity CA I isozyme in humans by studies on CA I-deficient individuals. On the other hand, CA II-deficient individuals exhibit abnormalities of bone, kidney and brain, implicating a functional role for the high-activity CA II isozyme in cells from these tissues and organs. It also appears that the CA II-deficient red cell is capable of normal respiratory function under unstressed conditions. In addition, there is some preliminary evidence that those organs such as the eye which primarily contain the CA II isozyme, may be able to function effectively in the absence of CA II.