ABSTRACT
The epididymis is a single convoluted tubule lined by a pseudostratified epithelium. Specialized epididymal epithelial cells, the so-called principal, basal, narrow, and clear cells, establish a unique luminal environment for the maturation and storage of spermatozoa. The epididymis is functionally and structurally divided into several segments and sub-segments that create regionally distinct luminal environments. This organ is immature at birth, and epithelial cells acquire their fully differentiated phenotype during an extended postnatal period, but the factors involved in this complex process remain incompletely characterized. In the adult epididymis, the establishment of an acidic luminal pH and low bicarbonate concentration in the epididymis contributes to preventing premature activation of spermatozoa during their maturation and storage. Clear cells are proton-secreting cells throughout the epididymis, but principal cells have distinct acid/base transport properties, depending on their localization within the epididymis. Basal cells are located in all epididymal segments, but they have a distinct morphology depending on the segment and species examined. How this structural plasticity of basal cells is regulated is discussed here. Also, the role of luminal factors and androgens in the regulation of epithelial cells is reviewed in relation to their respective localization in the proximal versus distal regions of the epididymis. Finally, we describe a novel role for CFTR in tubulogenesis and epithelial cell differentiation.
ABSTRACT
The epithelial principal cells are the predominant cell type of the epididymis. These cells have been shown to be both secretory and endocytic cells. The apical region of the cytoplasm of principal cells in the mongrel dog are located close to the cell apex and tubular lumen, and shown microvilli at the luminal border and present a endocytic apparatus, that consists of coated pits and vesicles, endosomes of varying size, multivesicular bodies, and lysosomes. The endosomes, multivesicular bodies and lysosomes contained the electron-dense patches. These results suggest that principal cells of the epididymis in the dog as possess a highly developed endocytic apparatus play a role in endocytosis. These cells function are similarly to the related in other mammals, in performing endocytosis.
Las células epiteliales principales son el tipo de célula que predominan en el epidídimo. Estas células han demostrado ser secretoras y endocíticas. La región apical del citoplasma de las células principales en el perro Mongrel, se encuentran muy cerca del ápice celular y lumen tubular, mostrando microvellosidades en el límite luminal y un aparato endocítico, el que consiste en depresiones recubiertas y vesículas, endosomas de diversos tamaños, cuerpos multivesiculares y lisosomas. Los endosomas, cuerpos multivesiculares y lisosomas contienen gránulos electrodensos. Estos resultados sugieren que las células principales del epidídimo, en el perro, poseen un aparato endocítico altamente desarrollado que juega un importante rol en la endocitosis. Estas células funcionan de manera similar a la correspondiente en otros mamíferos, en el desempeño de endocitosis.
Subject(s)
Animals , Male , Dogs , Epididymis/ultrastructure , Dogs/anatomy & histology , Epididymis/cytologyABSTRACT
The maintenance of potassium balance depends primarily on excretion by the kidney. The regulated secretion of potassium normally accounts for most of urinary potassium excretion. Potassium transport along the nephron has two main features:the ubiquitous Na,K-ATPase defines basolateral membranes, whereas site-specific potassium transporters are responsible for the apical transport. Two different cell types mediate secretion and reabsorption of potassium. Principal cells secrete potassium, whereas intercalated cells, especially those belonging to the subfamily of beta-intercalated cells, reabsorb potassium. The factors that stimulate potassium secretion by the principal cells include (1) increased extracellular fluid potassium concentration (2) increased aldosterone and (3) increased tubular flow rate. One factor that decreases potassium secretion is increased hydrogen concentration (acidosis). In situations associated with severe potassium depletion, there is a cessation of potassium secretion and net reabsorption of potassium. It is believed that H,K-ATPase transport mechanism located in the luminal membrane of the cortical and outer medullary collecting duct cells reabsorb potassium in exchange for hydrogen secreted into the tubular lumen.
Subject(s)
Acidosis , Aldosterone , Extracellular Fluid , Hydrogen , Kidney , Membranes , Nephrons , Phenobarbital , PotassiumABSTRACT
The cisternae of the Golgi apparatus of dog epididymal principal cells were labeled by the zinc iodide-osmium tetroxide method (ZIO). These cisternae were observed in the supranuclear region of the cytoplasm of the epididymal principal cells. Abundant endoplasmic reticulum cisternae, multivesicular bodies, mitochondria, lysosomes and vesicular elements of variable size were also found in this region, all associated with the sacks of the well-developed Golgi apparatus. The use of the ZIO method facilitates the observation and identification of the cisternae of the Golgi apparatus, thus permitting a correlation between structure and function in the so-called Golgi area. These ultrastructural characteristics support the secretory role of epididymal principal cells in the dog.
La cisterna del aparato de Golgi de las células principales del epidídimo del perro, fueron tratados con el método de tetróxido de zinc iodide-osmium (ZIO). Estas cisternas fueron observadas en la región supranuclear del citoplasma de las células principales del epidídimo. Abundante cisternas del retículo endoplasmático, cuerpos multivesiculares, mitocondrias, lisosomas y elementos vesiculares de tamaño variable, fueron encontrados en esta región, todos asociados con los sacos del aparato de Golgi maduro. El uso del método de ZIO facilita la observación e identificación del aparato de Golgi, permitiendo efectuar una correlación entre estructura y función en el área de Golgi. Estas características estructurales suponen el rol secretorio de las células epididimarias principales en el perro.
ABSTRACT
It has been reported that new apical anion exchanger perndrin, encoded by the pendred syndrome (PDS/pds, Slc26A4) gene, was expressed in the AE1-negative intercalated cells of rat and mouse kidneys. The purpose of this study was performed that expression of pendrin in the subtypes of intercalated cells in human kidney. The normal human renal tissues obtained from nephrotomized kidneys for renal cell carcinoma were fixed in periodate-lysine-paraformalde-hyde, and processed for immunohistochemistry. Subtypes of intercalated cells were identified by using antibodies for H(+)-ATPase and AE1, and connecting tubule cells and principal cells of collecting duct were identified using antibodies for calbindin D28K and AQP2, respectively. In human kidney, pendrin was expressed in the apical domain of AE1-negative intercalated cells including type B cells with diffuse and/or basolateal H(+)-ATPase, non A-non B (non -A/B) type intercalated cells with apical H(+)-ATPase and bipolar type of intercalated cells with apical and basolateral H(+)-ATPase. The AQP2-positive principal cells of cortical collecting duct were also had apical pendrin immunoreactivity. However, there was no pendrin immunoreactivity in AE1-positive type A intercalated cells, calbindin D28K-positive connecting tubule cells, and AQP2-positive medullary collecting duct. These results suggest that pendrin is an apical anion exchanger not only in the AE1-negative intercalated cells (type B, non-A/B and bipolar cells) but also in the principal cells of cortical collecting duct, and has an essential role in HCO3-secretion in human kidney.