Carbonic anhydrase VI in the mouse nasal gland.

Western blotting analysis of mouse nasal tissue using a specific anti-mouse secreted carbonic anhydrase (CA VI) antibody has shown that CA VI is present in this tissue. A single immunoreactive band of 42 kD was observed, as has been found previously for salivary tissues. RT-PCR analysis has shown that nasal mucosa expressed CA VI mRNA. By immunohistochemistry (IHC), CA VI was observed in acinar cells, in duct contents of the anterior gland of the nasal septum, and in the lateral nasal gland. The Bowman's gland, the posterior gland of the nasal septum, and the maxillary sinus gland were negative. Immunoreactivity was also observed in the mucus covering the respiratory and olfactory mucosa and in the lumen of the nasolacrimal duct. In contrast, an anti-rat CA II antibody (that crossreacts with the mouse enzyme) stained only known CA II-positive cells and an occasional olfactory receptor neuron. These results indicate that CA VI is produced by the nasal gland and is secreted over the nasal mucosa. By reversible hydration of CO(2), CA VI is presumed to play a role in mucosal functions such as CO(2) sensation and acid-base balance. It may also play a role in olfactory function as a growth factor in maturation of the olfactory epithelial cells.     

Carbonic anhydrase isozyme VI in rat lacrimal gland

Using monoclonal antibody specific to rat carbonic anhydrase isozyme VI (CA VI), the isozyme was localized in the lacrimal gland. A minority of acini (less than 10% of the total) contained a few immunoreactive acinar cells. Enzyme histochemistry indicated that the CA VI-positive cells were the only cells possessing CA in the lacrimal acini. In the acinar cells, the reaction product for CA VI was distributed in the secretory granules and cytosol between secretory granules. Except for mitochondrial enzyme (CA V) activity, the intracellular distribution of enzyme activity was similar to that of CA VI immunoreactivity, suggesting that rat lacrimal acinar cells contain only CA VI and CA V. CA VI in the secretory granules was discharged into the acinar lumen and is considered to carry out its function on the surface of the conjunctiva and cornea. The cytosolic CA VI may function in situ and be involved in electrolyte and water secretion by the acinar cells. Polyclonal antibody to rat erythrocyte CA (CA I and CA II) stained only the interlobular ducts. In contrast, all the ductal elements exhibited CA enzyme activity. This discrepancy between immunohistochemistry and enzyme histochemistry suggests the presence of CA isozyme(s) other than CA I, CA II and CA VI in the lacrimal duct.     

Redistribution of carbonic anhydrase VI expression from ducts to acini during development of ovine parotid and submandibular glands

 Carbonic anhydrase VI (CA VI) is a secreted enzyme produced predominantly by serous acinar cells of submandibular and parotid glands. We have investigated the developmental pattern of CA VI production by these glands in the sheep, from fetal life to adulthood, using immunohistochemistry. Also, a specific radioimmunoassay for CA VI was used to measure changes in enzyme expression in the parotid gland postnatally. CA VI is detectable by immunohistochemistry in parotid excretory ducts from 106 days gestation (term is 145 days), in striated ducts from 138 days and in acinar cells from 1 day postnatal. The duct cell content of CA VI declined as the acinar cell population increased, a feature also of CA VI immunoreactivity in the submandibular gland. Production of CA VI by submandibular duct cells was detectable initially at 125 days gestation, and acinar production was not seen before 29 days post-natal. Apart from the differing ontogeny of CA VI production in ducts and acini of parotid and submandibular glands, there was a parallel pattern of CA VI expression during the development of these major salivary glands.With the development of the acinar tissues in the postnatal lamb, there was a dramatic increase (about 600-fold) in the level of expression of CA VI in the parotid gland between days 7 and 59 as measured by radioimmunoassay. Accepted: 19 December 1996     

Secretion of carbonic anhydrase isoenzyme VI (CA VI) from human and rat lingual serous von Ebner's glands.

Salivary carbonic anhydrase VI (CA VI) appears to contribute to taste function by protecting taste receptor cells (TRCs) from apoptosis. The serous von Ebner's glands locating in the posterior tongue deliver their saliva into the bottom of the trenches surrounding the TRC-rich circumvallate and foliate papillae. Because these glands deliver their saliva directly into the immediate vicinity of TRCs, we investigated whether CA VI is secreted by the von Ebner's glands, using immunochemical techniques. The immunohistochemical results showed that CA VI is present in the serous acinar cells, ductal cells, and ductal content of von Ebner's glands and in the demilune and ductal cells plus ductal content of rat lingual mucous glands. More importantly, CA VI was also detected in taste buds and in the taste pores. Western blotting of saliva collected from the orifices of human von Ebner's glands and CAs purified from rat von Ebner's glands confirmed that CA VI is expressed in these glands and secreted to the bottom of the trenches surrounding the circumvallate and foliate papillae. These findings are consistent with the hypothesis that locally secreted CA VI is implicated in the paracrine modulation of taste function and TRC apoptosis. (J Histochem Cytochem 49:657-662, 2001)     

Immunohistochemistry of carbonic anhydrase isozymes VI and II during development of the rat salivary glands

 Secreted carbonic anhydrase (isozyme VI; CA VI) was localized by immunohistochemistry in the developing postnatal rat submandibular and parotid glands using a specific monoclonal antibody to the rat enzyme. CA VI immunostaining was not detectable in the glands before birth. In the submandibular gland, granular immunostaining for CA VI was detectable in several terminal tubule cells of 1-day-old rats. At 1 week, the CA VI-positive cells were located at the periphery of the terminal tubules and appeared to be budding off the tubules. These cellular buds gradually increased, and, by 4 weeks, formed acini. CA VI was also detected in the duct lumen from day 1. The immunostaining in the parotid gland was detected sporadically in the acinar cells at 2 or 3 weeks. By 4 weeks, when the gland was almost indistinguishable from the adult one, the number of positive acinar cells had increased. Their number, however, was far smaller than in the adult gland, and the enzyme could not be detected in the duct lumen. CA II was also localized using specific antibodies to the rat isozyme. CA II was detectable in the inter- and intralobular striated ducts at 2 weeks after birth in the submandibular gland and at 3 weeks in the parotid gland. These results suggset that CA VI is secreted into saliva from soon after birth and that CA II appears in parallel with the functional maturation of the ducts. In addition, CA II was transiently expressed by the cellular buds of the submandibular gland at 2 and 3 weeks. Accepted: 7 January 1998     

Distribution of epithelia and glands of the nasal septum mucosa in the rat.

A histotopographic study of the nasal septum mucosa in rats was made using semi-serial sections stained with PAS-hematoxylin, reconstructed in form of maps representing the structure in a sagittal plane. The stratified squamous, respiratory and olfactory epithelia and Masera's organ cover 14.8, 43.6, 41.6 and 1.8%, respectively, of the septal surface (117.1 mm2). In the vestibular region, only ducts of PAS-negative glands of the respiratory region are found, and below the septum there is the infraseptal gland with PAS-negative acini. In the respiratory region, PAS-negative acinous glands form two groups: the superior and the inferior one occupying 10.5 and 1.5%, respectively, of the septal area. PAS-positive acinous glands are in the inferior half of the respiratory region and in a small anteroinferior portion of the olfactory region. Besides goblet cells broadly distributed, the respiratory epithelium presents scattered intraepithelial PAS-positive glands which are concentrated in the anterior portion and close to the nasopharyngeal duct. In the olfactory region prevail Bowman's PAS-positive glands which are also present in the mucosa of Masera's organ, but are not seen in the olfactory mucosa of Jacobson's organ. In the latter, PAS-positive glands are found in the respiratory mucosa. Globular leukocytes, cells of connective tissue origin, are constantly infiltrating the superior regions of the respiratory and olfactory epithelia, being more numerous in female rats.     

Distribution of S-100 protein and its subunits in bovine exocrine glands

 The distribution of S-100 protein and its α- and β-subunits in bovine exocrine glands was studied by indirect immunohistochemistry. The entire spectrum of salivary glands, glands of the respiratory tract, intestinal glands, male and female genital glands, and skin glands was examined. S-100 and its β-subunit were identified in most serous secretory cells of mixed salivary glands, although secretory acini in some serous glands remained unreactive for these antigens. Mucous cells were constantly negative; mucoid cells were positive in the lacrimal and Harderian gland. The α-subunit of S-100 protein was identified in serous cells but the staining reaction was faint. Subunits of S-100 showed a characteristic distribution along the excretory duct systems of compound glands: S-100 and the β-subunit were present in intercalated duct epithelium, while striated duct epithelium stained for S100-α. Therefore, it is suggested that S100-α is related to resorption and secretion in striated ducts, while S100-β may govern acinar exocytosis and probably regulates proliferation and differentiation of glandular cells. Differing staining intensities for S-100 and its subunits in secretory cells of exocrine glands most probably indicate functional differences with regard to secretory activity and the cell cycle. Accepted: 11 February 1997     

Luminal leptin activates mucin-secreting goblet cells in the large bowel

Leptin has been suggested to be involved in tissue injury and/or mucosal defence mechanisms. Here, we studied the effects of leptin on colonic mucus secretion and rat mucin 2 (rMuc2) expression. Wistar rats and ob/ob mice were used. Secretion of mucus was followed in vivo in the rat perfused colon model. Mucus secretion was quantified by ELISA, and rMuc2 mRNA levels were quantified by real-time RT PCR. The effects of leptin alone or in association with protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) inhibitors on mucin secreted by human mucus-secreting HT29-MTX cells were determined. Leptin was detected in the rat colonic lumen at substantial levels. Luminal perfusion of leptin stimulates mucus-secreting goblet cells in a dose-dependent manner in vivo in the rat. Leptin (10 nmol/l) increased mucus secretion by a factor of 3.5 and doubled rMuc2 mRNA levels in the colonic mucosa. There was no damage to mucosa 24 h after leptin, but the number of stained mucus cells significantly increased. Leptin-deficient ob/ob mice have abnormally dense mucus-filled goblet cells. In human colonic goblet-like HT29-MTX cells expressing leptin receptors, leptin increased mucin secretion by activating PKC- and PI3K-dependent pathways. This is the first demonstration that leptin, acting from the luminal side, controls the function of mucus-secreting goblet cells. Because the gel layer formed by mucus at the surface of the intestinal epithelium has a barrier function, our data may be relevant physiologically in defence mechanisms of the gastrointestinal tract.     

Distribution of T-cell subsets and immunoglobulin-containing cells in nasal-associated lymphoid tissue (NALT) of chickens

The present study demonstrated the localization of the T-cell subsets (CD4+ and CD8+) and immunoglobulin (Ig)-containing cells (IgA, IgM, and IgG) in the nasal mucosa and its accessory structures. These lymphoid structures may be compared with nasal-associated lymphoid tissue (NALT) of rats and mice. In the chicken NALT, T-cell subsets were more widely distributed than Ig-containing cells, especially in large lymphoid accumulations restricted to the respiratory mucosa in the nasal cavity and the nasolacrimal duct. These lymphoid accumulations in the mucosa of the nasal cavity and nasolacrimal duct consisted of widely distributed CD8+ cells and deeply aggregated CD4+ cells adjacent to large germinal centers. In these lymphoid accumulations, IgG-containing cells were more frequently observed than IgM- and IgA-containing cells. T-cell subsets, predominantly CD8+ cells were more widely distributed in the duct epithelium of the lateral nasal glands than Ig-containing cells. Moreover, numerous CD8+ cells and a few Ig-containing cells were found in the chicken salivary glands, especially around the orifice of their ducts into the oral cavity. Therefore, it seems likely that the chicken NALT plays an important part in the upper respiratory tract, with a close relationship to the paraocular immune system.     

Acinar origin of CFTR-dependent airway submucosal gland fluid secretion

Cystic fibrosis (CF) airway disease arises from defective innate defenses, especially defective mucus clearance of microorganisms. Airway submucosal glands secrete most airway mucus, and CF airway glands do not secrete in response to VIP or forskolin. CFTR, the protein that is defective in CF, is expressed in glands, but immunocytochemistry finds the highest expression of CFTR in either the ciliated ducts or in the acini, depending on the antibodies used. CFTR is absolutely required for forskolin-mediated gland secretion; we used this finding to localize the origin of forskolin-stimulated, CFTR-dependent gland fluid secretion. We tested the hypothesis that secretion to forskolin might originate from the gland duct rather than or in addition to the acini. We ligated gland ducts at various points, stimulated the glands with forskolin, and monitored the regions of the glands that swelled. The results supported an acinar rather than ductal origin of secretion. We tracked particles in the mucus using Nomarski time-lapse imaging; particles originated in the acini and traveled toward the duct orifice. Estimated bulk flow accelerated in the acini and mucus tubules, consistent with fluid secretion in those regions, but was constant in the unbranched duct, consistent with a lack of fluid secretion or absorption by the ductal epithelium. We conclude that CFTR-dependent gland fluid secretion originates in the serous acini. The failure to observe either secretion or absorption from the CFTR and epithelial Na(+) channel (ENaC)-rich ciliated ducts is unexplained, but may indicate that this epithelium alters the composition rather than the volume of gland mucus.     

Histological and Histochemical Analysis of the Gastrointestinal Tract of the Common Pipistrelle Bat (Pipistrellus Pipistrellus)

Bats have a very high mass-specific energy demand due to small size and active flight. European bat species are mostly insectivorous and the morphology of the gastrointestinal (GI) tract should be adapted accordingly. This study investigated the general anatomy by histology and the function by analysing carbohydrate distribution in particular of the mucus of the GI tract of the insectivorous bat Pipistrellus pipistrellus. The GI tracts of three individuals were dissected, fixed in formaldehyde, and embedded in paraffin wax. The tissues and cells of the GI tract of P. pipistrellus were analysed by classical (acid alizarin blue, haematoxylin-eosin, and Masson Goldner Trichrome), histochemical (periodic acid-Schiff, Alcian blue at pH 2.5) and lectin histochemical (lectins WGA and HPA) staining procedures. The GI tract of P. pipistrellus is organised into the typical mammalian layers. The short, narrow, and thin-walled esophagus is simple with a folded stratified squamous epithelium without glands but mucous surface cells secreting neutral mucus. The stomach is globular shaped without specialisation. Mucous surface cells produced neutral mucus whereas neck and parietal cells secreted a mixture of neutral and acid mucus. Chief cell surface was positive for N-acetylglucosamine and the cytoplasm for N-acetylgalactosamine residues. The intestine lacked a caecum and appendix. The small intestine was divided into duodenum, jejunum-ileum and ileum-colon. The epithelium consisted of columnar enterocytes and goblet cells. The large intestine is short, only represented by the descending colon-rectum. It lacked villi and the mucosa had only crypts of Lieberkühn. Towards the colon-rectum, goblet cells produced mucus with N-acetylglucosamine residues increasing in acidity except in colon-rectum where acidity was highest in the base of crypts. Along the tube the surface of enterocytes was positive for N-acetylglucosamine and N-acetylgalactosamine. All over the mucus filling the lumen of the GI tract was positive for N-acetylglucosamine and increased in acidity in all parts except of the stomach.In conclusion, the simple GI tract showed an anatomical reduction of tissue enabling for a short retention time and a reduction of the load carried during flight: short GI tract, lack of lymphoid tissue, missing of glands in certain regions, and a distinct pattern of mucus distribution, indicating different physiological functions of these areas. The GI tract of P. pipistrellus was typical for an insectivorous species probably representing the ancestral condition.Key words: Chiroptera, esophagus, glycoconjugates, intestine, lectins, stomach     

In situ visualization of o-phthalate esters in gastrointestinal tract of the frog Rana esculenta

The regional distribution and relative occurrence of phthalates were studied immunohistochemically by confocal laser scanning microscopy in the alimentary tract of the green frog, Rana esculenta, using an antibody against o-phthalate esters. Many positive sites indicating the basal presence of phthalate esters were identified. The immunoreactive cells were located in the gastric glands of the stomach and in the intestinal epithelium regions with variable frequencies. The regional distribution of phathalate-accumulating cells resembled that of fish and demonstrated that these endocrine disruptors not only enter via the alimentary canal, but also bioaccumulate inside cells specialized in secretion as well as absorption functions.     

Occurrence of the mucinous differentiation antigen CA125 in genital tract and conductive airway epithelia of diverse mammalian species (rabbit, dog, monkey)

CA125 is a human tumor-associated antigen of coelomic epithelial origin. In the present study, immunohistochemical analysis of normal rabbit, dog, and monkey tissues using monoclonal antibody OC125, revealed that in these animals positive staining for CA125 is found in all tissues that produce this mucin-like glycoprotein in man, i.e., the peritoneal and pleural mesothelium, the different Müllerian-duct-derived epithelia of the female genital tract, and the epithelium of trachea, bronchi, bronchioli, and mucoserous respiratory glands; CA125 was also detected in some ductal and acinar cells of the dog mammary gland. Without trypsin treatment of sections, staining was predominantly localized on the apical cell surface of all mentioned cell types. After treatment, mucin droplets inside respiratory mucous cells were also positively stained. In all cases, staining was associated with material positive for periodic acid-Schiff (PAS) and Alcian blue. In rats, its presence could not be demonstrated. Our results show that the CA125 epitope is not restricted to man and that its expression throughout different animal species is associated with well-defined tissue compartments. The expression of the mucous differentiation antigen CA125 in several common laboratory animals provides new opportunities for the experimental study of its biological significance.     

Brunner's glands: a structural, histochemical and pathological profile

Brunner's glands are unique to mammalian species and in eutherians are confined primarily to the submucosa of the proximal duodenum. In the majority of species examined, they begin at the gastrointestinal junction and extend for variable distances distally in the wall of the proximal small intestine. Ducts of individual glands empty either directly into the intestinal lumen or unite with overlying intestinal glands (crypts of Lieberkühn) dependent on the species. Secretory units of Brunner's glands consist of epithelial tubules that show frequent distal branchings. The secretory units, with the exception of those found in rabbits and horses, consist primarily of a mucin producing cell type. However, other cell types normally associated with the overlying intestinal epithelium may be encountered scattered within the secretory units reflecting the developmental origin of these glands. Secretion from Brunner's glands contributes to a layer of mucus that forms a slippery, viscoelastic gel that lubricates the mucosal lining of the proximal intestinal tract. The unique capacity of this mucus layer to protect delicate underlying epithelial surfaces is due primarily to the gel-forming properties of its glycoprotein molecules. Mucin glycoproteins produced by Brunner's glands consist primarily but not exclusively of O-linked oligosaccharides attached to the central protein core of the glycoprotein molecule. Human Brunner's glands produce class III mucin glycoproteins and are thought to be the product of mucin gene MUC6 which is assigned to chromosome 11 (11p15-11p15.5 chromosome region). In addition to mucin glycoproteins and a limited amount of bicarbonate, numerous additional factors (epidermal growth factor, trefoil peptides, bactericidal factors, proteinase inhibitors, and surface-active lipids) have been identified within the secretory product of Brunner's glands. These factors, incorporated into the mucus layer, guard against the degradation of this protective barrier and underlying mucosa by gastric acid, pancreatic enzymes, and other surface active agents associated with this region. Yet other factors produced by Brunner's glands function to provide active and passive immunological defense mechanisms, promote cellular proliferation and differentiation, as well as contribute factors that elevate the pH of luminal contents of this region by promoting secretion of the intestinal mucosa, pancreatic secretion and gall bladder contraction. Additional insights concerning the role of Brunner's glands in the mammalian gastrointestinal tract as well as their possible evolution in this class of vertebrates have been gained from a basic understanding of their pathobiology.     

Mucopolysaccharides in bronchial secretion of children.

The diseases of respiratory system are nowadays one of the important medical, economical and social problems of modern civilization. A common symptom of these diseases regardless of their etiology, character, klinical manifestation and morphological findings is hypersecretion of bronchial sputum. Tracheobronchial mucus is produced by mucous bronchial glands and goblet cells. This mucus represents at physiological condition about 5 micrometer thick cover on mucous of nasopharynx, larynx, trachea, bronchi up to terminal bronchioles. Protective function of mucus cover resposes in mechanical and humoral barrier and also in removing the inhaled particles and their transport to the upper part of the respiratory system. In spite of the fact, that bronchial secretion has an important role in protective mechanism and in thermal and water exchange of respiratory tract, this secretion is not sufficiently scrutinized mainly of children yet.     

Cell-specific expression of CYP2A5 in the mouse respiratory tract: effects of olfactory toxicants.

We performed a detailed analysis of mouse cytochrome P450 2A5 (CYP2A5) expression by in situ hybridization (ISH) and immunohistochemistry (IHC) in the respiratory tissues of mice. The CYP2A5 mRNA and the corresponding protein co-localized at most sites and were predominantly detected in the olfactory region, with an expression in sustentacular cells, Bowman's gland, and duct cells. In the respiratory and transitional epithelium there was no or only weak expression. The nasolacrimal duct and the excretory ducts of nasal and salivary glands displayed expression, whereas no expression occurred in the acini. There was decreasing expression along the epithelial linings of the trachea and lower respiratory tract, whereas no expression occurred in the alveoli. The hepatic CYP2A5 inducers pyrazole and phenobarbital neither changed the CYP2A5 expression pattern nor damaged the olfactory mucosa. In contrast, the olfactory toxicants dichlobenil and methimazole induced characteristic changes. The damaged Bowman's glands displayed no expression, whereas the damaged epithelium expressed the enzyme. The CYP2A5 expression pattern is in accordance with previously reported localization of protein and DNA adducts and the toxicity of some CYP2A5 substrates. This suggests that CYP2A5 is an important determinant for the susceptibility of the nasal and respiratory epithelia to protoxicants and procarcinogens.     

Characterization of lacrimal gland carbonic anhydrase VI.

We have previously demonstrated by immunohistochemistry the presence of secreted carbonic anhydrase (CA VI) in the acinar cells of the rat lacrimal glands. In this study we purified the sheep lacrimal gland CA VI to homogeneity and demonstrated by Western analysis that it has the same apparent subunit molecular weight (45 kD) as the enzyme isolated from saliva. RT-PCR analysis showed that CA VI mRNA from the lacrimal gland was identical to that of the parotid gland CA VI mRNA. An RIA specific for sheep CA VI showed the lacrimal gland tissue concentration of the enzyme to be 4.20 +/- 2.60 ng/mg protein, or about 1/7000 of the level found in the parotid gland. Immunohistochemistry (IHC) and in situ hybridization (ISH) showed that lacrimal acinar cells expressed both immunoreactivity and mRNA for CA VI. Moreover, CA VI immunoreactivity was occasionally observed in the lumen of the ducts. Unlike the parotid gland, in which all acinar cells expressed CA VI immunoreactivity and mRNA, only some of the acinar cells of the lacrimal gland showed expression. These results indicate that the lacrimal gland synthesizes and secretes a very small amount of salivary CA VI. In tear fluid, CA VI is presumed to have a role in the maintenance of acid/base balance on the surface of the eye, akin to its role in the oral cavity.     

Immunocytochemistry of ion transport mediators in the genital tract of female rodents

With immunocytochemistry, we have determined distribution of sodium, potassium-adenosine triphosphatase (Na+, K+-ATPase) and of three isoenzymes of carbonic anhydrase (CA) and have shown absence of the chloride channel, Band 3 protein, in the genital tract of female rodents. Staining for Na+,K+-ATPase was strongest in the ampullary oviduct and uterine glands in the mouse. In the mouse and rat ovary, immunostaining evidenced CA I, II, and III in theca interna cells where the enzyme could affect the pH of follicular fluid. The zona pellucida of the ovary and cytoplasmic foci in follicular granulosa cells stained for content of only CA I in mouse ovary, suggesting synthesis of a zona pellucida component by granulosa cells. CA II in mouse oviductal epithelium increased from the negative infundibulum to the variably positive ampulla and isthmus to the uniformly positive interstitial segment. The content of CA III varied inversely to that of CA II. The prevalence of CA II-positive cells apparently corresponded with that of nonciliated cells, whereas abundance of CA III-positive cells concurred with that of ciliated cells in regions of the mouse oviduct. The rat oviduct lacked CA II but, like that of the mouse, showed CA III in the proximal region. The staining for CA II in surface epithelium exceeded the reactivity in glandular epithelium in the mouse uterus, except during estrus. In contrast, rat uterus evidenced CA II in glandular but not surface epithelium. These results testify to possible significance of various ion transport mechanisms for biologic activities of diverse cells in the female genital tract.     

Immunohistochemical localization of carbonic anhydrase isoenzymes in the human male reproductive tract

The distribution of human carbonic anhydrase (HCA) isoenzymes I, II and VI in the human male reproductive tract was studied using specific antisera against affinity purified isoenzymes in conjunction with the peroxidase-antiperoxidase complex method. HCA VI-specific staining could not be demonstrated in any of the tissues studied, and HCA I was observed only in red blood cells. Immunostaining denoted HCA II in the epithelia of the seminal vesicle, ampulla of the ductus deferens and distal ductus deferens. Some cells in the epithelium of the corpus and cauda epididymidis also stained for HCA II. The staining for HCA II in the epithelium of the reproductive tract declined from the strongly positive seminal vesicle to the proximal part of the ductus deferens, which stained negatively. There were also HCA II-positive particles derived from the apical protrusions of the epithelium in the lumina of the seminal vesicle, ampulla of the ductus deferens and ductus deferens. The physiological role of HCA II is linked to the secretion of bicarbonate into the seminal plasma and thereby to the regulation of sperm motility and pH in the seminal plasma.