Biomedical subjects

W W Minuth

Publications and source records attributed to W W Minuth.

At least 55 records · Page 3Linked to original sources

PubMed1988

The expression of specific proteins in cultured renal collecting duct cells.

It is still uncertain whether cell cultures attain the functional maturity of corresponding in vivo cells. The degree of differentiation of cultured collecting-duct (CD) epithelium cells was therefore examined using immunohistochemical procedures. Three monoclonal antibodies (mabs CD1, CD2, and CD3) were raised against proteins (PCD) isolated from the renal papilla. At Western-blot analysis, each of these antibodies reacted with a specific protein that was distinguishable according to its molecular weight [PCD1, 190 kilodaltons (kDa); PCD2, 210 kDa; PCD3, 50 kDa]. Using immunofluorescence, these proteins were found to be localized exclusively in the renal CD system. Other renal structures, such as the proximal or distal tubular portions, the glomeruli and the interstitial network, were not reactive. The mabs, CD2 and CD3, labeled both the cortical and medullary CD in a uniform way, whereas mab CD1 produced heterogeneous immunolabeling along the length of the cortical, medullary, and papillary CD. As revealed by immunohistochemistry, the mabs revealed differences with respect to the expression of the specific renal proteins in cultured CD cells. In polar-differentiated epithelium cultured for 5 days on a specific renal support, mab CD1 was unreactive, whereas mabs CD2 and CD3 were positive. This demonstrated the biochemical immaturity of this cultured epithelium with respect to CD1 reactivity. In morphologically dedifferentiated CD monolayer cells grown on the bottom of a culture dish, only a weak reaction for mab CD3 was observed. The loss of epithelial polarization in CD monolayer cells obviously coincides with the absence of the renal proteins PCD1 and PCD2.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1988

Apico-basal osmotic gradient induces transcytosis in cultured renal collecting duct epithelium.

The present experiments report the existence of an apico-basal plasma membrane shuttle in cultured renal collecting duct principal cell epithelium. Apical and basal perfusion under isotonic conditions, 290 mosm phosphate-buffered saline (PBS), has no effect on the shape of the epithelium. In contrast, gradient perfusion of the epithelium with 75 mosm PBS on the apical side and 290 mosm PBS on the basal side for 10 min alters the morphology of the epithelium by causing the originally columnar epithelial cells to become lower, the intercellular spaces to dilate, and the intracellular vesicles to enlarge. Perfusion of the epithelium with isotonic PBS in the presence of electron-dense cellular markers such as gold-coupled GPCDI antibody, recognizing a glycoprotein in the plasma membrane of collecting duct cells (W.W. Minuth, G. Lauer, S. Bachman and W. Kriz, Histochemistry 80:171-182, 1984), cationized ferritin (CF), horseradish peroxidase (HRP) and native ferritin (NF) for 10 min reveals their binding at the apical plasma membrane. Little endocytosis is observable. However, after labeling the luminal side by the cellular markers and following exposure to apical hypotonicity, 75 mosm PBS for 10 min, endocytosis of all markers is enhanced to a high degree. Furthermore, the gold-coupled GPCDI antibody and cationized ferritin are transported within vesicles unidirectionally through the epithelium and are exocytosed at the basolateral aspect, indicating the retrieval and possible translocation of apical plasma membrane. In contrast, volume markers such as NF and HRP are also endocytosed under osmotic gradient exposure, but are not seen to be transcytosed. Therefore, the function of this membrane pathway seems not to be related to water reabsorption, but may be part of a cellular response as protection against the osmotic gradient.

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PubMed1988

Ionic conductances of cultured principal cell epithelium of renal collecting duct.

The ionic conductive properties were studied of epithelia of collecting duct principal cells which had been grown in primary tissue culture from renal cortex/capsule explants. When pretreated with aldosterone (10(-6) mol/l) and bathed on either surface with isotonic HCO3(-)-free Ringer's solution, the transepithelial voltage, Vte, varied between -21 and -72 mV (apical surface negative) while the transepithelial resistance, Rte, ranged from 0.4 to 1.5 k omega cm2. By 10:1 step-changes in Na+ concentration the apical cell membrane was shown to have a high conductivity for sodium, inhibitable by amiloride, 10(-6) mol/l. However, contrary to observations in natural collecting duct under control conditions, amiloride never reversed the polarity of Vte even at 10(-4) mol/l. Both the apical and the basolateral cell membranes were conductive for potassium and both conductivities were inhibitable by Ba2+ (5 mmol/l). 10:1 reduction of apical Cl- concentration strongly hyperpolarized Vte with a monophasic time course suggesting the presence of a paracellular shunt conductance for Cl-. In addition there may be a small Cl- conductance present in the apical cell membrane since apical application of the chloride channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPAB) at 10(-7) mol/l produced a minute but significant hyperpolarization. On the other hand, 10:1 reduction of basolateral Cl- concentration caused a biphasic change in Vte (initial depolarization, followed by repolarization) which indicates the presence of a large Cl- conductance in the basolateral cell membrane. The latter was not inhibitable by 10(-7) mol/l NPPAB. Higher concentrations of this and of an other Cl-channel blocker produced non-specific effects.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1988

Appearance of specific proteins in the apical plasma membrane of cultured renal collecting duct principal cell epithelium after chronic administration of aldosterone and arginine vasopressin.

Principal cell epithelium of renal collecting duct from neonatal rabbit kidney was cultured in the presence of aldosterone (1 x 10(-6) M) and arginine vasopressin (AVP; 1 x 10(-6) M) for 10 days to investigate, by immunohistochemical methods using specific monoclonal antibodies, whether the hormones influence the expression and insertion of plasma membrane proteins. The experiments demonstrated that aldosterone alone or aldosterone plus AVP significantly increased the number of epithelial cells reacting at the luminal and lateral plasma membrane with the antibodies CD 2 and 3, specific for renal collecting duct, as we have shown in the kidney. In cultures treated with aldosterone and aldosterone plus AVP, nearly all epithelial cells were labelled by the antibodies, while controls or AVP treatment showed 41% and 24% unreactive cells, respectively. These findings were complemented with electrophysiological experiments, in which epithelia pretreated by aldosterone or aldosterone plus AVP showed significantly hyperpolarized transepithelial voltage (Vte) and higher resistance (Rte) than controls or AVP-treated specimens. The experiments demonstrated that chronic administration of aldosterone or of aldosterone plus AVP to increase Na+-transport was paralleled by the appearance of collecting-duct-specific proteins in the epithelium. Consequently, this result indicates that aldosterone influences the functional maturity of the cultured epithelium.

Aldosterone↗

PubMed1988

Complex physiological and biochemical action of aldosterone in toad urinary bladder and mammalian renal collecting duct cells.

Since the discovery of the steroid hormone aldosterone nearly 35 years ago, our knowledge on the cellular actions of aldosterone is still incomplete. Most of the present physiological and biochemical knowledge about the antinatriuretic action was revealed by investigations on amphibian tight epithelia, in particular the toad urinary bladder. Less biochemical information was obtained from mammalian tissue such as microdissected renal tubules and cultured cells. In our opinion, it is questionable whether de novo synthesis of cell proteins-induced by aldosterone-can explain all of the hormonal effects to increase the Na+ transport. In the present paper we try to analyze the wide and contradictory field of biochemical data about the action of aldosterone on the increase in Na+ transport in renal cells in an attempt to incorporate this information into an extended working hypothesis. We suggest distinguishing principally between an early and a late biochemical response phase. We speculate that aldosterone may act by a two-step mechanism: the early and late aldosterone-induced proteins.

Aldosterone↗

PubMed1987

Microheterogeneity of the collecting duct system in rabbit kidney as revealed by monoclonal antibodies.

This report describes the immunolocalization of three monoclonal antibodies along the collecting duct system in rabbit kidney. The antibodies were raised against antigens derived from a membrane fraction of homogenized papillary tissue. Western Blot analysis demonstrated that each of the antibodies recognized a single band of about 190,000 (PCD1), 210,000 (PCD2) and 50,000 (PCD3) daltons. In renal tissue, the antibodies bound specifically to the epithelia of the connecting tubule (CNT), the collecting duct (CD) and the papillary surface epithelium. Differences in the binding patterns of the antisera were limited to the cortex. PCD1 labeled only a few scattered cells in the CNT, and exhibited a heterogeneous binding along the cortical collecting duct (CCD). PCD2 and PCD3 binding patterns were similar. In the CNT, these antibodies bound to the intercalated cells (IC-cells) but not to the CNT-cells proper. In the CCD, both IC-cells and principal cells were labeled. The binding to the medullary collecting duct by all three antisera was identical. The ureter was labeled only by PCD2 and PCD3, and none of the antisera bound to the bladder epithelium. The antibody binding patterns provide information concerning tubular axial heterogeneity and embryogenetic aspects of the CNT and the CCD. These antibodies may be used as differentiation markers in studies of the developing kidney and of renal tissue culture systems.

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PubMed1987

Electron-microscopic immunogold localization of a collecting-duct antigen (PCD2) in intercalated and principal cells of rabbit kidney.

A monoclonal antibody against an antigen (PCD2) derived from the rabbit renal papilla recognized principal and intercalated cells of the collecting duct system in the adult rabbit kidney. Intercalated cells were heterogeneous in the connecting tubule and the cortical collecting duct, where immunoreactive and unreactive cells were shown to coexist. In the outer medullary collecting duct, all intercalated cells exhibited PCD2-immunoreactivity. Connecting tubule cells proper were not recognized by the antibody, whereas all principal cells of the collecting duct revealed specific immunoreactivity. The immunocytochemical heterogeneity of the intercalated cells is discussed in terms of a functional heterogeneity. Cytologically, the immunogold labeling of principal and intercalated cells was shown to occur along the plasmalemma, in the intracellular membrane structures and along the Golgi transport route. This pattern suggests that the antigenic determinant, which is ubiquitous in both principal and reactive intercalated cells, belongs to a membrane protein.

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PubMed1987

High-conductance K+ channel in apical membranes of principal cells cultured from rabbit renal cortical collecting duct anlagen.

Using the patch clamp technique, one type of K+ channel was identified in the apical cell membrane of cultured principal cells of rabbit renal collecting ducts in the cell-attached or excised-patch configuration. The channel was highly selective for K+ over Na+ (typically 30-70-fold) and had a conductance of 180, SD +/- 39 pS (n = 6), referred to a situation of 140 mmolar K+-Ringer solution present on either surface of the patch membrane. Channel activity was completely blocked by Ba2+ (5 mmol/l) and partially inhibited by Na+. The latter was evidenced by a deviation from Goldman rectification at high cytoplasm-positive membrane potentials, which was observed when Na+ competed with K+ for channel entrance from the cytoplasmic surface. Channel open probability depended strongly on membrane voltage and cytoplasmic Ca2+ concentration. Open-close kinetics exhibited double exponential behaviour, with a strong voltage dependence of the slow open time constant. Infrequently also a substate conductance level was identified. The voltage and calcium dependence suggest that the channel plays a role in adjusting K+ secretion to Na+ absorption in the fine regulation of cation excretion in renal collecting ducts.

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PubMed1987

Expression of the alpha-subunit of Na/K-ATPase in renal collecting duct epithelium during development.

Aldosterone enhances synthesis and enzyme activity of Na/K-ATPase and has been found to stimulate sodium reabsorption by the renal cortical collecting duct. Moreover, chronic exposure to aldosterone is associated with a remarkable morphological-functional adaptation. This is seen as a magnification in basolateral membrane area of principal cells. In the present paper we investigated the acquistion of Na/K-ATPase alpha-subunit in renal tissue and examined whether aldosterone initiates functional and adaptive changes in cultured collecting duct cells similar to those observed in vivo. Using a monoclonal antibody, immunofluorescence microscopy demonstrated the acquisition of the alpha-subunit of Na/K-ATPase in the developing cortical collecting ducts of the kidney of neonatal rabbits. The mature collecting ducts in the medulla and papilla of the developing kidney were strongly labelled at the basolateral side, while in the cortical portion of the fetal collecting duct adjacent to the embryonic ampullae the immunolabel was found at the apical and the basolateral aspect of the epithelium. However, the embryonic collecting duct ampullae in the outer cortex did not show any reaction with the antibody. In the collecting duct cells cultured for 24 hours the alpha-subunit of Na/K-ATPase was found to be distributed at both the apical and basolateral aspect of the epithelium. After two to 16 days, the immunolabel was strictly found distributed at the basolateral side. Culturing collecting duct cells in the presence of aldosterone (10(-6) M), the hormone modulated the cellular shape of epithelia after five days by infolding the lateral plasma membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1987

Neonatal rabbit kidney cortex in culture as tool for the study of collecting duct formation and nephron differentiation.

By stripping off the capsula fibrosa of neonatal rabbit kidneys a consistently thin tissue layer consisting of collecting duct anlagen, S-shaped bodies and nephrogenic blastema is obtained. This thin layer seems to be an excellent object for investigation of epithelium formation and nephron differentiation. Three different tissue culture protocols are described: 1. A polarly differentiated collecting duct epithelium with 'tight' characteristics consisting only of principal cells, grown on specific renal support 2. A morphologically dedifferentiated collecting duct principal cell monolayer grown on the unspecific bottom of a plastic culture dish 3. An embryonic tissue layer with numerous S-shaped bodies which might be a suitable model for investigation of the development of maturing nephron structures in serum-free culture medium.

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PubMed1987

Methylation of cytosolic proteins may be a possible biochemical pathway of early aldosterone action in cultured renal collecting duct cells.

The common model of aldosterone-dependent sodium transport is that the hormone increases sodium transport during the "early" and "late" response phases by inducing specific proteins (AIPs). However, in actual biochemical studies, AIPs were mostly detected 6-24 h after aldosterone application. Regarding the physiological early response phase, this implies temporal dissociation of the physiological and biochemical events. The discrepancy raises the question as to whether other biochemical events, such as protein modifications, may be involved in addition to the novo protein synthesis. Labelling of cultured renal collecting duct epithelia for 1-5 h with a radioactive methylgroup donor, S-adenosyl methionine (SAM), following tissue fractionation, resulted in progressive methylations of specific cytosolic proteins. Aldosterone-dependent methylations increased consistently with time, and accounted for a 60% increase in total cytosolic protein content as compared to controls after 5 h labelling. The different methylated proteins showed a molecular weight of 220, 97 and 75 kd and comprised groups of proteins with an isoelectric point of 5.1-5.7 and 6.0-7.5. Methylation of identical proteins was obtained by incubation of the epithelia with unlabelled SAM instead of aldosterone. SAM-induced as well as aldosterone-induced methylation of proteins with an isoelectric point of 6.0-7.5 could be inhibited by the methylation inhibitor S-adenosylhomocysteine. The results indicate that aldosterone may influence the SAM cycle in cultured collecting-duct epithelia during increase of the Na+-transport.

Aldosterone↗

PubMed1986

Long-term culture of renin containing tissue.

Thin cortical tissue explants from kidneys of hydronephrotic mice were excised and incubated in different culture media containing growth and proliferation factors. Over a period of several months the content of renin in the explants and in the culture medium was repeatedly measured, to define the conditions necessary for the maintenance of renin production in a long-term culture. The best results were obtained when culturing the renal tissue in Dulbecco's medium (DMEM) with 10% fetal calf serum, 6 units/100 ml platelet-derived growth factor and 200 ng/ml glycylhistidyllysine. Renin was still present within the cells and in the culture medium after more than six months. Prevention of dedifferentiation, as evidenced in this case by the maintenance of renin production, seemed to be dependent on specific extracellular matrix proteins of renal origin. If the explants were dissociated from their matrix components by collagenase, a gradual loss of renin production was observed within 5 days. Complementation of the collagenase-digested cell suspension with different nonrenal extracellular matrix materials did not afford the stabilizing effect of the original pericellular matrix.

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PubMed1986

Electrical properties of renal collecting duct principal cell epithelium in tissue culture.

Whereas collecting duct epithelium in vivo is composed of principal and intercalated cells, we grew a pure principal cell epithelium using a new technique involving tissue culture. These principal cells were derived from collecting duct anlagen of newborn rabbits. We investigated the electrical properties of such epithelia in a newly designed lucite double-chamber with an inner opening of 0.08 cm2. Our observations were: mean transepithelial resistance Rte was 0.83 +/- 0.2 k omega cm2 at 37 degrees C and after preincubation in aldosterone; mean transepithelial potential difference Vte was low and variable under standard conditions and at room temperature but increased to -59.5 +/- 4.4 mV (sign referring to polarity of apical surface) after preincubation in 10(-6) mol/l aldosterone and at 37 degrees C; 10(-6) mol/l amiloride added to the apical perfusion fluid largely abolished this Vte while increasing Rte by 120%; experiments with 5 X 10(-3) mol/l BaCl2 in the apical perfusion fluid failed to change Rte and Vte significantly. This principal cell epithelium therefore has characteristics of a "tight" epithelium with active sodium transport; however, its electrical properties differ from those of the isolated perfused collecting duct segment.

Aldosterone↗

PubMed1986

Differentiation properties of renal collecting duct cells in culture.

In the present study, we were particularly interested in distinguishing specific patterns of structural and functional proteins in the collecting duct system of neonatal and adult kidneys and in cultured renal collecting duct epithelia in order to ascertain the degree of differentiation in the cultures. We studied the distribution of specific renal collecting duct cell markers using morphological, immunohistochemical and biochemical procedures. Cultured renal collecting duct epithelium undergoes maturation in vitro. Examples of morphological differentiation include the appearance of cilia and microvilli at the apical cell pole, and a basement membrane at the basal aspect of the epithelium. Tight junctions with five to seven strands separate the wide intercellular spaces from the apical cell surface. Physiological maturation from a 'leaky' to a 'tight' epithelium is evident from the acquisition of the alpha-subunit of Na/K-ATPase and the development of a high transepithelial potential difference and resistance. Biochemical differentiation is revealed by the expression of specific proteins. The simple-epithelium cytokeratins, PKK1 and PKK2, which are typical intracellular-matrix proteins of mature collecting duct epithelium, maintain the same distribution in cell culture as in neonatal and adult kidneys. An indicator of maturation in vitro is the expression of the collecting duct-specific proteins, PCD2 and PCD3. Newly developed monoclonal antibodies against these antigens reacted similarly with cultured cells and cells of the mature collecting duct system, but they did not label the embryonic ampullae in the cortex of neonatal rabbit kidneys. In contrast, a third collecting duct-specific protein, PCD1, is not expressed by the cultured cells, which indicates the retention of an embryonic characteristic in vitro. Embryonic collecting duct ampullae of the neonatal kidney in situ contain laminin during their development. Laminin is, however, absent in cultured collecting duct epithelium. Biochemical stimulation of the adenylate cyclase system by arginine vasopressin resulted in a twofold stimulation of the enzyme activity. This degree of stimulation is similar to that found in maturing kidneys of neonatal rabbits and indicates another embryonic feature of the cultures.

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PubMed1985

Selective ADH-induced hypertrophy of the medullary thick ascending limb in Brattleboro rats.

A morphometric study was undertaken to quantitate the morphologic changes induced by ADH availability in the rat kidney. Homozygous Brattleboro rats with hereditary diabetes insipidus (DI) (no ADH) were compared to heterozygous Brattleboro control rats (HZ) and to DI rats after 5 to 6 weeks of continuous ADH infusion by implantable Alzet osmotic minipumps (TDI). ADH resulted in a 37% increase in mass of kidney per unit body wt. All kidney zones and all nephron segments were not increased uniformly. The inner stripe was enlarged more than other renal zones. It represented 15.5 +/- 0.7% of the total kidney height along the cortico-papillary axis in DI and 22.2 +/- 1.5% in TDI (P less than 0.025). The volume of the inner stripe in DI and TDI amounted to 10.9 +/- 0.9 and 18.0 +/- 1.0% of the total kidney volume, respectively (P less than 0.001). Selective increases in tubular diameter and cell height, due mostly to an hypertrophy of pre-existing cells, were observed in the earliest part of the thick ascending limbs (TAL) in the inner stripe, resulting in a twofold increase in epithelial volume per unit tubular length (P less than 0.001). Volume density of mitochondria and surface density of basolateral membranes were unchanged but, due to the increase in cell volume and inner stripe thickness, the amount of mitochondria and the surface area of basolateral membrane in the TAL were more than tripled in the inner stripe of treated rats. These changes provide a much greater salt transport capacity in the TAL of treated rats. They probably represent an adaptation of the early TAL to an enhanced sodium chloride transport in response to a direct ADH stimulation and/or to an increased salt delivery to this segment in the concentrating kidney.

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PubMed1984

Immunohistochemical localization of a protein fraction derived from rabbit renal papilla.

Studies were carried out to define antigenic characteristics of the rabbit renal collecting duct. Renal papillae of adult rabbits were homogenized, centrifuged, and the 600 X g pellet was extracted with 0.5% Triton X-100 in the presence of 1 M NaCl. The crude extract was fractionated on an anion exchange column (DEAE cellulose). A fraction enriched in acidic proteins that co-purified with a radioactive 150 kd glycoprotein from cultured collecting duct cells (Minuth 1982), was used for immunization of guinea pigs. The antiserum shows the following characteristics as revealed by indirect immunofluorescence on the rabbit kidney: 1) Among all tubular epithelial cells only principal cells of the collecting duct and the connecting tubule cell show immunoreactivity. 2) The antiserum decorates the epithelial-interstitial interface of the whole collecting duct as well as of connecting tubule and thick ascending limb of Henle's loop. 3) There is immunoreactivity of interstitial fibers throughout the kidney. 4) Epithelial cells in a variety of other organs in rabbit did not react with the antiserum. Our data demonstrate an antigenic distinction of both, the connecting tubule cell and the principal cell, discriminating these cells from other tubular epithelial cells including the intercalated cells of the collecting duct system. Furthermore, our findings point to a heterogeneity along the distal nephron with respect to the constituents of the epithelial-interstitial interface.

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PubMed1984

Effects of glycoprotein and basement membrane synthesis inhibitors on the growth of cultured renal collecting duct epithelium.

The biochemical and morphological extent of glycoprotein synthesis inhibition of cellular and extracellular proteins was studied on cultured renal collecting duct (CD) epithelium. We found that tunicamycin (4 micrograms/ml) inhibits the glycosylation of a 150,000 d glycoprotein (gpCDI). A 85,000 d glycoprotein (gpCDII) was not affected. The inhibition by tunicamycin demonstrates that gpCDI has characteristics of a N-glycan, whereas gpCDII seems to be an O-glycan. 6-diazo-5-oxo-norleucine (4 X 10(-5) M) which was used as glutamine analogue, did not show a comparable inhibitory effect as seen with tunicamycin. The lack of effect of norleucine demonstrates that glutamine is not the locus of glycosylation in both proteins. However, because of the tunicamycin inhibition it points to asparagine as the site of glycosylation in the gpCDI. Long term cultures of the tissue up to 15 days in the presence of tunicamycin and norleucine and of substances usually used as basement membrane inhibitors, such as hydroxy-D-proline (1 mM), L-azetidine-2-carboxylic acid (1 mM) and o- and p-nitrophenyl-xylopyranoside 1 mM), revealed that it is possible to eliminate completely the fibroblasts beneath the cultured epithelium and within the degenerating corematerial. Experiments with hydroxy-D-proline showed the most striking effect. Experiments with L-azetidine-2-carboxylic acid and nitrophenyl-xylopyranoside resulted in the elimination of fibroblasts and dedifferentiation of the collecting duct epithelium.

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PubMed1984

Immunocytochemical localization of a renal glycoprotein (gpCDI) synthesized by cultured collecting duct cells.

A sulfated, proline-rich glycoprotein (gpCDI, apparent molecular weight 200,000 in column chromatography and 150,000 in SDS-PAGE) was isolated from cultured renal collecting duct epithelium by centrifugation. Triton X100 extraction and DEAE-cellulose ion exchange chromatography. A DEAE-cellulose ion exchange chromatography fraction with the enriched gpCDI was used for immunization of guinea pigs. The antiserum was prepared for antigen localization by indirect immunofluorescence in collecting duct cell cultures and in tissue sections of neonatal and adult rabbit kidneys. In the cultured collecting duct epithelium, antibody staining of the epithelium and structures of the extracellular matrix was age dependent. Cultures of dedifferentiated collecting duct monolayers revealed positive reaction in the cytoplasm. In neonatal and adult rabbit kidneys, the antibody was localized in the entire collecting duct system but not in the collecting duct ampullae of the newborn kidney. Staining of the cytoplasm was found only in medullary collecting ducts of the neonatal kidney; other portions revealed staining mostly at the basal circumference of the tubule and at the luminal cell borders. Apart from collecting ducts, no other tubular segments were reactive. The cortical and the medullary interstitium contained fluorescent fibres which were concentrated around vascular structures. A possible relation between gpCDI and collagenous compounds is discussed. Bowman's capsule reacted positively, whereas staining of the mesangial matrix was weak. The localization of the antigen, as revealed by indirect immunofluorescence, suggests that gpCDI occurs both in intracellular and extracellular (interstitial) location. Two main points are emphasized: Firstly gpCDI is considered an important constituent in different stages of collecting duct development, and secondly, the staining pattern of the antibody varies with the different portions of both young and adult kidney collecting ducts; this staining heterogeneity may correspond with the known regional differences of collecting duct functions.

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