Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

Abstract

The nonciliated cells lining the ductuli efferentes presented three distinct cytoplasmic regions. The apical region contained, in addition to cisternae of endoplasmic reticulum and mitochondria, two distinct membranous elements. The tubulovesicular system consisted of dilated tubules connected to the apical plasma membrane and subjacent distended vesicular profiles. The apical tubules, not connected to the cell surface, consisted of numerous densely stained tubules of small size which contain a compact, finely granulated material. The supranuclear region, in addition to a Golgi apparatus and ER cisternae, contained dilated vacuoles, pale and dense multivesicular bodies, as well as numerous dense granules identified cytochemically as lysosomes. The basal region contained the nucleus and many lipid droplets. The endocytic activity of these cells was investigated using cationic ferritin (CF) and concanavalin-A-ferritin (Con-A-ferritin) as markers of adsorptive endocytosis; and native ferritin (NF), concanavalin-A-ferritin in the presence of alpha-methyl mannoside, and horseradish peroxidase or albumin bound to colloidal gold for demonstrating fluid-phase endocytosis. These tracers were injected separately into the rete testis, and animals were sacrificed at various time intervals after injection. At 1 min, CF or Con-A-ferritin were seen bound to the apical plasma membrane, to the membrane of microvilli, and to the membrane delimiting elements of the tubulovesicular system. Between 2 and 5 min, these tracers accumulated in the densely stained apical tubules and at 15 min in the dilated vacuoles. Between 30 min and 1 hr, the tracers appeared in multivesicular bodies of progressively increasing density, whereas at 2 hr and later time intervals, many dense lysosomal elements became labeled. The tracers for fluid-phase endocytosis showed a distribution similar to that for CF or Con-A-ferritin except that they did not bind to the apical plasma membrane, microvilli, or membrane delimiting the tubulovesicular system. At no time interval were any of the tracers observed in the abluminal spaces. Thus, the nonciliated epithelial cells of the ductuli efferentes are actively involved in fluid-phase and adsorptive endocytosis, both of which result in the sequestration of endocytosed material within the lysosomal apparatus of the cell.

Morphological analysis of endocytosis in efferent ductules of estrogen receptor‐α knockout male mouse

“…Endocytosis alone cannot account for the total capacity of reabsorption of this epithelium (Jones and Jurd, 1987). The presence of an elaborate morphological system for active movement of fluids from the lumen to internal compartments of the cell suggests, however, that endocytosis plays an important role in efferent ductule function (Hermo and Morales, 1984;Hermo et al, 1988Hermo et al, , 1991a. In the present study, we show that ER␣ presence is necessary for the maintenance of the morphological components of this endocytotic apparatus.…”

“…Actin filaments in microvilli apparently participate in the movement of membrane components into the endocytotic pits that form between microvilli (Gottlieb et al, 1993). Thus, with the loss of membrane associated with microvilli in the ␣ERKO epithelium, a decrease in the number of tubular coated pits, apical tubules, and other structures of the endocytotic apparatus (Hermo and Morales, 1984;Hermo et al, 1988Hermo et al, , 1994 would be expected.…”

“…Three major pathways have been reported for the epithelium to reabsorb the fluid. First, the nonciliated cells have a well-developed endocytotic apparatus in the apical cytoplasm such as invaginations of the apical membrane, vesicles, endosomes, multivesicular bodies and lysosomes (Hermo and Morales, 1984;Jones and Jurd, 1987;Hermo et al, 1988Hermo et al, , 1991bRobaire and Hermo, 1988). Studies using electron dense tracers confirmed that these organelles are involved in endocytosis (Hermo and Morales, 1984;Veeramachaneni and Amann, 1991;.…”

“…First, the nonciliated cells have a well-developed endocytotic apparatus in the apical cytoplasm such as invaginations of the apical membrane, vesicles, endosomes, multivesicular bodies and lysosomes (Hermo and Morales, 1984;Jones and Jurd, 1987;Hermo et al, 1988Hermo et al, , 1991bRobaire and Hermo, 1988). Studies using electron dense tracers confirmed that these organelles are involved in endocytosis (Hermo and Morales, 1984;Veeramachaneni and Amann, 1991;. Second, it is proposed that electrolytes and consequently water are reabsorbed across the epithelium by means of membrane-associated transporters and channels (Ilio and Hess, 1992;Clulow et al, 1998;Fisher et al, 1998).…”

Localização histoquímica de algumas hidrolases no epidídimo do gerbilo

“…Atualmente, se conhece que a função hidrolítica da FoAc está ligada aos processos de digestão autofágica e heterofágica dos lisossomos, os quais estão presentes principalmente no citoplasma apical de células epiteliais dos dúc-tulos eferentes 8 e do ducto epididimário 6,9 , justificando a sua atividade enzimática na parte apical do epitélio tubular destes ductos da via espermática 8 . A sugestão proposta de que o segmento inicial é a principal região epididimária associada à reabsorção de fluido seminal 6 fora antes sugerida 3,6,10 pelas reações distintas para adenosina trifosfatase (ATPase) e fosfatase alcalina na margem microvilosa do segmento inicial.…”