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H Renneberg

Publications and source records attributed to H Renneberg.

At least 19 recordsLinked to original sources
PubMed2002

Effects of dexamethasone on proliferation of and fibronectin synthesis by human primary prostatic stromal cells in vitro.

Glucocorticoids are anti inflammatory stress hormones and have been suggested to be involved in a large number of pathological processes. To test the effects of glucocorticoids on stromal prostatic cell growth and proliferation in vitro, the influence of a synthetic glucocorticoid (dexamethasone, dex) on recently established human primary cells from prostatic stroma (hPCPs) was analysed. The localization and distribution of the glucocorticoid receptor (GR) was investigated by immunohistochemistry. In addition, expression of the active isoform of the receptor (alpha-GR) was examined by reverse transcription PCR, and the effect of different doses of dex on proliferation of the stromal cells evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and amido black assays. alpha-GR mRNA was expressed by the hPCPs, and the GR protein was detected in the cytoplasm and nucleus of these cells. Incubating the cells with dex resulted in an enhanced cell proliferation that was mainly restricted to the fibroblasts. Moreover, fibronectin (FN) gene expression and secretion of the protein was increased by high doses of dex (> or = 10(-8) M), whereas low doses of dex (10(-10)M) showed no effect. Human prostatic stromal cells show sensitivity to dex in vitro, resulting in an increase in cell proliferation and FN synthesis. The authors assume that locally accumulating glucocorticoids can also influence the regulation of cell growth and extracellular matrix synthesis in the human prostate in vivo and may play a role in the pathologically altered prostate.

Cell Division↗
PubMed2002

Detection of thyroid peroxidase mRNA in peripheral blood of patients with malignant and benign thyroid diseases.

The aim of this study was to evaluate thyroid peroxidase (TPO) mRNA expression in peripheral blood of patients with benign and malignant thyroid disease. Included were 120 thyroid cancer patients, 85 patients with goitre or Graves' disease (GD) and 54 healthy volunteers. TPO mRNA expression was analysed in peripheral blood by nested RT-PCR. In cancer patients, RT-PCR results were compared with staging, grading and serum thyroglobulin (TG) measurement. TPO transcripts were detected in 7/10 (70%) patients with known metastases of thyroid cancer and in 39 of 110 (36%) patients without metastases (P<0.05), in 15/44 (34%) patients with goitre, in 17/41 (41%) cases with GD and in 4/54 (7.4%) subjects in the control group (P<0.05, controls vs all patients with thyroid disease). Among cancer patients without metastatic disease, RT-PCR results correlated positively with lymph node status (P=0.05), grading (P=0.01) and elevated serum thyroglobulin levels (P=0.03). This is the largest study investigating the use of the TPO-RT-PCR assay. Positivity in TPO-RT-PCR correlates significantly with metastatic disease in cancer patients and with the presence of thyroid disease in general. To date, TPO-RT-PCR cannot substitute for standard techniques in the diagnosis of local recurrence or metastatic spread in thyroid cancer patients. However, as results of TPO-RT-PCR correlate significantly with lymph node status, grading and serum TG measurements in patients with non-metastatic disease, TPO seems to be an interesting molecular marker to look at in follow-up studies.

Adult↗
PubMed2001

Identification and characterization of neutral endopeptidase (EC 3. 4. 24. 11) from human prostasomes--localization in prostatic tissue and cell lines.

BACKGROUND: An antibody directed against a 100 kDa protein was immunoselected from a polyvalent antiserum against human prostasomes. The antibody as well as biochemical characteristics of the respective antigen were used to study the structural relationship of the latter with prostate membrane specific antigen (PMSA), another 100 kDa membrane protein of the prostate. METHODS: The isolated purified 100 kDa protein was characterized by tryptic degradation, aminoacid-sequencing and mass spectroscopy peptide-fingerprinting as well as mono-saccharide analysis and lectin binding and identified as a prostasomal neutral endopeptidase (NEP, EC 3.4.24.11). Immunohistochemistry, immunoelectron microscopy, in situ hybridization, and RT-PCR were performed to analyze the expression and distribution of the protein in normal and malignant human prostatic tissues and cell lines. RESULTS: Prostatic NEP, which has no relationship with PMSA, is a glycosylated, integral membrane protein type II. The prevalent glycosyl residues are NeuNAc, GlcNAc, GalNAc, Gal, Man, Fuc. NEP-mRNA is expressed in human prostatic epithelial and some stromal cells. NEP-immunoreactivity is strong in normal prostatic epithelium and confined to the apical plasma membrane. During apocrine secretion, the enzyme is released from the secretory cells, contributing to the formation of prostasomes. In prostate cancer specimens, immunoreactivity of apical plasma membranes is lost, while generalized cytoplasmic immunoreactivity develops. CONCLUSIONS: Prostatic secretory cells contain a membrane-bound, highly glycosylated neutral endopeptidase which is restricted to the apical plasma membrane. The enzyme is released from the cells in an apocrine fashion and contributes to the formation of prostasomes. In prostate cancer cells a preferential cytoplasmic localization is observed, pointing to alterations in intracellular targeting.

Amino Acid Sequence↗
PubMed2001

Semiquantitative morphology of human prostatic development and regional distribution of prostatic neuroendocrine cells.

BACKGROUND: The neuroendocrine cells of the human prostate have been related to proliferative disorders such as prostatic cancer. Their origin, distribution, and development have therefore been studied and discussed in terms of current stem cell concepts in the prostate. METHODS: Prostatic tissue specimens (n = 20) from human fetuses (n = 8), prepubertal and pubertal children (n = 8) and mature men (n = 4) were studied immunohistochemically using antibodies directed against neuroendocrine, epithelial as well as secretory markers. Semiquantitative computer-assisted evaluation of different epithelial and stromal components based on stereological principles was performed on azan-stained sections representative of all developmental stages. RESULTS: By the end of gestational Week 9, neuroendocrine (NE) cells appear in the epithelium of the urogenital sinus and are subsequently closely associated with the formation of urethral prostatic buds. The fetal and postnatal distribution pattern of NE cells within the gland is characterized by a relatively constant number of cells per gland similar to prostatic smooth muscle cells. Likewise, a density gradient exists with the highest density in the large collicular ducts and almost no NE cells in subcapsular peripheral acini. In peripheral ducts, the distribution is random. Maturation of the NE cells precedes that of the secretory cells by about 10-16 years. CONCLUSIONS: A second prostatic stem cell lineage, different from the urogenital sinus (UGS)-lineage is hypothesized originating from immature neuroendocrine cells. Being morphologically indistinguishable from the UGS-derived prostatic secretory cell lineage, it gives rise to neuroendocrine cells. Their presence is apparently important for proliferation regulation of the UGS-derived lineage of the prostate.

Adolescent↗
PubMed2001

Assessment of fibronectin as a potential new clinical tool in andrology.

In this prospective clinical study, 892 patients with normal and impaired semen were examined in order to investigate the correlation between the concentration of fibronectin in seminal plasma and the motility of spermatozoa. The fibronectin concentration in seminal plasma, total sperm motility and linear sperm motility were measured. We report here a significant negative correlation between the fibronectin concentration in seminal plasma and total sperm motility (r=-0.3474). There was no link between varicocele and vasectomy, or between varicocele and variation in the concentration of fibronectin. It is concluded that higher concentrations of the acute-phase protein fibronectin may be a cause of severe reduction in sperm motility. The investigation of fibronectin concentrations in seminal fluid could be a new and helpful clinical tool in the assessment of male fertility.

Adolescent↗
PubMed2001

Purification and characterization of macrophage migration inhibitory factor as a secretory protein from rat epididymis: evidences for alternative release and transfer to spermatozoa.

BACKGROUND: The cytokine macrophage migration inhibitory factor (MIF), originally described as a T cell product, has recently been identified to mediate cellular interactions in several endocrine organs. Western blots analysis of rat epididymal homogenates using an anti-MIF antibody indicated the presence of substantial amounts of an immunoreactive protein with the apparent Mr of 12 kDa. Our study aimed to characterize the molecular nature of this immunoreactive factor. MATERIALS AND METHODS: The purified 12 kDa protein and a cloned cDNA fragment were characterized by sequence analysis. Furthermore, expression pattern and localization of the 12 kDa protein were investigated using in situ hybridization, immunohistochemistry, immunoelectron microscopy, and western blots experiments on epididymal sections, isolated epididymal vesicles, and outer dense fibers from spermatozoa. RESULTS: The N-terminal amino acid sequence analysis over 10 amino acids revealed a 100% homology of the 12 kDa protein to the N-terminus of the cytokine MIF. These data were confirmed by sequence analysis of a reverse transcription polymerase chain reaction (RT-PCR) amplified cDNA fragment from rat epididymis, which also showed complete homology to the MIF cDNA sequence. MIF protein and mRNA were localized in the epithelial cells of the epididymis in a regional distribution manner, with the expression maximal in the caput. Immune cells were not labeled. MIF is the first classical cytokine identified to be expressed by the epididymal epithelial cells. Immunoelectron microscopy detected MIF immunoreactivity in the cytoplasm, with no reaction visible in the Golgi complex and the cisternae of the endoplasmic reticulum. At the apical cell surface, MIF accumulated in stereocilia and vesicles that were pinched off from the plasma membrane. MIF detection in vesicles isolated from epididymal secretion together with the lack of a N-terminal signal sequence for translocation in the endoplasmic reticulum strongly suggested a nonclassical secretion mode. Furthermore, MIF was identified as a new component of the outer dense fibers (ODF), a cytoskeletal element of the mid- and principal piece of the sperm tail. CONCLUSION: The cytokine MIF was identified in substantial amounts in the epithelial cells of rat epididymis and in the outer dense fibers of rat epididymal spermatozoa. Our results indicate a nonclassical secretion mode for MIF and suggest a cell-to-cell transfer of MIF via vesicles to the sperm cells.

Animals↗
PubMed2000

Cell lineage characteristics of human prostatic stromal cells cultured in vitro.

BACKGROUND: An in vitro model of prostatic stromal cells suitable for experimental studies of the pathogenesis of BPH is still lacking. We therefore standardized the isolation, cultivation, and characterization of human prostatic stromal cell lineages. METHODS: Stromal cells were isolated from a surgical specimen of BPH. Using antibodies specific for either epithelial or stromal cells of the human prostate, the isolated cells were morphologically and immunohistochemically characterized. Viability and functional activity were assessed by proliferation assays and stimulation experiments. Gene expression was monitored by RT-PCR. RESULTS: In early passages (P8), cells showed a high purity (>/=98%) for stromal markers; about 60% displayed the characteristics of fibroblasts, and the remaining 40% were classified as smooth muscle cells. In late passages (P20), the proportion of muscle cells declined to 10%. Stimulation experiments including basic fibroblast growth factor (bFGF) resulted in enhanced proliferation, whereas dihydrotestosterone (DHT), estrogen, and flutamide did not influence proliferation. Gene expression studies demonstrated a positive signal for androgen receptor and keratinocyte growth factor (KGF). CONCLUSIONS: Prostatic stromal cells can be propagated several times and show karyotypic stability for up to 18 subculture experiments. The ratio of myoid and fibroblastic cells can be used for standardization of cell cultures with stable characteristics.

Cell Division↗
PubMed2000

The significance of serum levels of insulin-like growth factor-1 in patients with prostate cancer.

OBJECTIVES: To compare the serum levels of insulin-like growth factor-1 (IGF-1) in patients with prostate cancer and in control patients with no malignancy, and to evaluate any possible influence of testicular androgen withdrawal on the level of IGF-1 in patients with prostate cancer. PATIENTS AND METHODS: IGF-1 was measured in serum samples from 238 patients using both a chemiluminescence method and a radio-immunoassay. From a subgroup of 19 patients presenting with newly diagnosed carcinoma of the prostate, IGF-1 and testosterone values were measured before and during the course of testicular androgen withdrawal, achieved by the administration of luteinizing hormone-releasing hormone (LHRH) analogues combined with anti-androgens. RESULTS: There were no significant differences in the mean serum levels of IGF-1 patients with and without prostate cancer (158.6 and 159.1 ng/mL, respectively). There were no significant differences in mean IGF-1 levels before and after antiandrogen therapy; the mean (median, SD, range) levels of testosterone (microg/L) and IGF-1 (ng/mL) before androgen withdrawal were 4.81 (4.84, 1.26, 3.11-6.93) and 157.1 (152.5, 26.7, 122.8-195. 1). After androgen withdrawal the corresponding values were 0.303 (0. 218, 0.24, 0.13-0.81) and 169.7 (31.7, 168.6, 124.9-227.6). A linear regression analysis (P = 0.76) and Spearman rank order correlation test (correlation coefficient -0.0613, P = 0.64) showed no association between levels of testosterone and IGF-1. Freeze and thaw cycles applied to the samples had no effect on the IGF-1 values measured. CONCLUSIONS: There was no significant association between IGF-1 serum levels and prostate cancer. Short-term androgen withdrawal using LHRH analogues combined with anti-androgens had no effect on the levels of IGF-1.

Aged↗
PubMed2000

Molecular detection of thyroglobulin mRNA transcripts in peripheral blood of patients with thyroid disease by RT-PCR.

The sensitive detection of circulating tumour cells in patients with differentiated thyroid cancer may precede the detection of relapse by other diagnostic studies--such as serum thyroglobulin-and thus may have important therapeutic and prognostic implications. We performed reverse transcription-polymerase chain reaction (RT-PCR) on blood samples from patients diagnosed with thyroid disease using two different RT-PCR sensitivities. Additionally, tissue specificity of TG mRNA-expression was determined using RNA extracts from 27 different human tissues. The lower limit of detection was 50-100 TG mRNA producing cells/ml blood using a 'normal' RT-PCR sensitivity and 10-20 cells/ml blood using a 'high' sensitivity. With the normal sensitivity TG mRNA was detected in 9/13 patients with thyroid cancer and metastasis, 63/137 patients with a history of thyroid cancer and no metastasis, 21/85 with non-malignant thyroid disease and 9/50 controls. With the high sensitivity TG mRNA was detected in 11/13 patients with thyroid cancer and metastasis, 111/137 patients with a history of thyroid cancer and no metastasis, 61/85 with non-malignant thyroid disease and 41/50 controls. Interestingly, using the normal RT-PCR sensitivity TG mRNA transcripts are specific for thyroid tissue and detectable in the peripheral blood of controls and patients with thyroid disease, which correlates with a diagnosis of metastasized thyroid cancer. However, with a high RT-PCR sensitivity, TG mRNA expression was found not to be specific for thyroid tissue and was not correlated with a diagnosis of thyroid cancer in patients. As a consequence, to date TG mRNA detected by RT-PCR in the peripheral blood cannot be recommended as a tumour marker superior to TG serum-level.

Case-Control Studies↗
PubMed2000

Mesenchymal entactin-1 (nidogen-1) is required for adhesion of peritubular cells of the rat testis in vitro.

Epithelial-like Sertoli cells isolated from immature rat testis aggregate to form tubule-like structures when cultured on a monolayer of mesenchyme-derived peritubular cells. At the end of this morphogenetic process both cell types are separated by a basement membrane. In this study the gene expression of monocultures and direct cocultures of peritubular cells and Sertoli cells was examined using DD-RT-PCR. One of the isolated cDNA clones showed high homology to the cDNA encoding the basement membrane component entactin-1 (nidogen-1). Even though the entactin-1 (nidogen-1) gene is transcribed in peritubular cells, Sertoli cells, and in direct cocultures, the mRNA is translated only by the peritubular cells. No entactin-1 (nidogen-1) was detected in the Sertoli cells by Western blotting. Moreover, peritubular cell monocultures and cocultures showed the presence of one single band at 152 kDa in the supernatant, whereas in cell lysates two bands were detectable at 152 kDa and 150 kDa. Perturbation experiments using monoclonal antibodies directed against entactin-1 (nidogen-1) were performed with peritubular cells and Sertoli cells, respectively, and demonstrated loss of cell adhesion of the peritubular cells, while the Sertoli cells remained adherent. From these data we conclude that entactin-1 is exclusively produced and secreted by mesenchymal peritubular cells, and affects adhesion of peritubular cells in an autocrine manner.

Animals↗
PubMed2000

Transforming growth factor-beta2 mediates mesenchymal-epithelial interactions of testicular somatic cells.

Transforming growth factor-beta2 (TGFbeta2) is an important mediator of growth and differentiation. We here describe for the first time the complete sequence of the TGFbeta2 complementary DNA derived from peritubular myoid cells of the rat testis. The size of the rat TGFbeta2 complementary DNA was 1245 bp, and the deduced protein sequence contained 414 amino acids. Sequence comparison with the human and mouse amino acid sequences demonstrated 96.4% and 97.9% sequence identities, respectively. To elucidate the functional role of TGFbeta2 in testicular somatic cells, we studied its secretion in vitro in monocultures and cocultures of mesenchymal peritubular and epithelial Sertoli cells. The highest amounts of TGFbeta2 protein were secreted in the cocultures and by peritubular cells, whereas Sertoli cells secreted only minor amounts. Stimulation experiments with FSH revealed a reduced secretion of TGFbeta2 in cocultures, probably mediated by a paracrine interaction of the FSH-responsive Sertoli cells. In contrast, TGFbeta2 secretion by peritubular cells was increased after stimulation with glucocorticoids and after addition of recombinant TGFbeta2, indicating an autoregulation of TGFbeta2. Furthermore, application of recombinant TGFbeta2 to cocultures resulted in an enhanced aggregation and cell clustering of Sertoli cells, pointing to an important role of TGFbeta2 in the paracrine interaction of peritubular and Sertoli cells of the developing rat testis.

Amino Acid Sequence↗
PubMed1999

Localization of protein gene product 9.5 immunoreactivity in derivatives of the human Wolffian duct and in prostate cancer.

BACKGROUND: Protein gene product 9.5 (PGP 9.5) has been considered to be a neuronal marker, but it is also present in extraneuronal tissues, e.g., the human mammary gland and rat epididymis. Its presence and distribution in the developing and adult male human genital tract have been unknown. METHODS: Immunohistochemical reactions were performed on human embryonic and postnatal specimens of the male genital tract, using commercial monoclonal and polyclonal antibodies. RESULTS: PGP 9.5 immunoreactivity was found in the Wolffian duct of human embryos (55-85 mm crown-rump length). Strong reactivity was observed in mesonephric tubular cells and at the apical rim of Wolffian duct cells. Owing to their PGP 9.5 immunoreactivity, these cells could also be identified on the surface of the embryonic verumontanum, extending from the orifices of the Wolffian duct to a small stretch of the urogenital sinus. There they contrasted sharply against non-Wolffian cells. In the adult human genital tract, PGP 9.5 immunoreactive material was present in the supranuclear portion of some epithelial cells of the epididymal efferent ductules, in isolated cells of the ejaculatory ducts, and in prostate cancer specimens. In the ejaculatory ducts, the PGP 9.5-immunoreactive cells were free of immunoreactivity for semenogelin, the major secretory product of the ejaculatory-vesicular-ampullary complex, and they also lacked chromogranin A-immunoreactivity. In prostate cancer specimens, PGP 9.5 immunoreactivity was never observed in secretory cells (immunoreactive for prostate-specific antigen), but was restricted to neuroendocrine cells, where it occurred either alone or coexpressed with chromogranin A-immunoreactivity. CONCLUSIONS: PGP 9.5-immunoreactivity is prenatally distributed in the Wolffian duct and its derivations; postnatally, it is restricted to a few cells derived from the initial and terminal segment of the Wolffian duct, and to neuroendocrine cells in prostate cancer specimens.

Adult↗
PubMed1999

Prostate specific membrane antigen (PSM) is expressed in various human tissues: implication for the use of PSM reverse transcription polymerase chain reaction to detect hematogenous prostate cancer spread.

Detection of prostate-specific membrane antigen (PSM)-mRNA expression in blood samples using reverse transcription polymerase chain reaction (RT-PCR) is discussed as a new diagnostic marker of circulating micrometastases in prostate cancer patients. We applied the RT-PCR technique to different human tissues and obtained positive signals for PSM transcripts in human genital and multiple extra-genital tissue sites. The cDNAs were prepared from different human tissues and prostatic cell lines. RT-PCR and nested RT-PCR for PSM was performed with primers derived from the published PSM cDNA. The RT-PCR fragments obtained were cloned and showed 100% sequence homology to PSM. Southern blot hybridization with labeled probes was used to confirm the specificity of the amplicons. In addition to the known PSM expression in the human brain, PSM-mRNA was detected in cDNA isolated from human testis, epididymis and seminal vesicles and in the PC-3 prostatic cancer cell line. Furthermore, we found PSM-mRNA in heart, liver, lung, kidney, spleen, and thyroid gland. The results indicate that PSM expression is not restricted to the prostate gland, but represents a more general component of genital and extra-genital human tissues. This must be considered when RT-PCR and nested RT-PCR screening for PSM expression is performed as a diagnostic measure in blood from prostate cancer patients.

Antigens, Surface↗
PubMed1999

Fibronectin in human prostatic cells in vivo and in vitro: expression, distribution, and pathological significance.

In the present study we examined the expression and release of the extracellular matrix glycoprotein fibronectin (FN) in a prostate cancer cell line (LNCaP) and in primary prostatic stromal cells using the reverse transcription-polymerase chain reaction (RT-PCR) and by an enzyme-linked immunosorbent assay. Perturbation experiments in vitro using antibodies directed against FN and the FN receptor were also performed. Immunohistochemistry was used to show the in vivo distribution of FN and the FN receptor in tissue sections of normal human prostate, benign prostatic hyperplasia, and prostate carcinoma. The expression of the oncofetal FN ED-B segment in benign prostatic hyperplasia and prostate carcinoma tissue was investigated by RT-PCR. The FN mRNA was expressed by LNCaP and primary prostatic stromal cells, respectively. Both cell types released FN into the medium in a time-dependent manner, whereby FN secretion was about 2.5-fold higher in cultures of stromal cells relative to LNCaP cells. Blocking FN with anti-FN antibodies resulted in a significant decrease in cell adhesion for LNCaP cells and a change in morphology for the primary stromal cells. FN was located mainly in the stromal compartment of the prostate, showing a distinct distribution pattern in prostate carcinoma, whereas the FN receptor was detectable only in the prostate epithelia. RT-PCR experiments showed the expression of the oncofetal FN ED-B segment in benign prostatic hyperplasia and prostate carcinoma tissue, with a 3.5-fold higher expression in the prostate carcinoma probes. Our data point to an important role for FN in cell adhesion of prostatic cells and show that an alternatively spliced FN mRNA is upregulated in the pathologically altered human prostate.

Animals↗
PubMed1999

Simultaneous apocrine and merocrine secretion in the rat coagulating gland.

The coagulating gland of the rat synthesizes two prevalent secretory proteins (transglutaminase and 115 K) that are discharched in a different manner, one being secreted in an apocrine fashion (transglutaminase) and the other one in a merocrine way (115 K). Differences in the intra- cellular pathway and the release of either protein were studied using immunofluorescence on semithin sections, immunoelectron microscopy of preembedding-processed chopper sections and postembedding-processed ultrathin sections of rat coagulating gland. Immunohistochemical staining using an anti-transglutaminase antibody resulted in dense labeling of the cytoplasm of secretory cells and their apical blebs, whereas the cisternae of the rough endoplasmic reticulum and the Golgi apparatus were completely unlabeled. When, on the contrary, the anti-115 K antiserum was used, dense labeling of the cisternae of the rough endoplasmic reticulum, the Golgi apparatus, and the secretory granules was seen. Intraluminal secretion was also labeled, but the secretory blebs remained unlabeled. Our findings show that, in the coagulating gland of the male rat, the two secretory proteins studied are processed in parallel, but at completely different intracellular pathways. They are released via different extrusion mechanisms. Transglutaminase is synthesized outside the endoplasmic reticulum, reaches the apical cell pole by free flow in the cytoplasm, and is released via apocrine blebs, the membranes of which appear to be derived from the apical plasma membrane. The protein 115 K, on the other hand, follows the classic route, being synthesized within the cisternae of rough endoplasmic reticulum, subsequently glycosylated in the Golgi apparatus, and released in a merocrine fashion. The mutual exclusion of the two secretory pathways and the regulation of the alternative release mechanism are still unresolved issues.

Animals↗
PubMed1999

Serum albumin as a potential carrier for the apocrine secretion of proteins in the rat coagulating gland.

A protein of 66k was purified to homogeneity from the total secretion of rat coagulating gland. Its close structural relationship to serum albumin was demonstrated by N-terminal amino acid sequence analysis, proteolytic fingerprinting and Western blotting studies using polyclonal antibodies raised against the 66k protein and rat serum albumin. Immunofluorescence staining showed that the 66k protein was localised in the cytoplasm of coagulating gland epithelial cells from which it is released via apocrine blebs. Performing immunoelectron microscopy, the 66k protein was by no means detectable in the endoplasmic reticulum and the Golgi apparatus. Reverse transcription-PCR, Northern blotting studies and in situ hybridisation experiments demonstrated that mRNA of albumin is not expressed by coagulating gland epithelial cells. Therefore, intravascular albumin should be transferred into the epithelial cells of the rat coagulating gland followed by secretion via aposomes. Furthermore, overlay blots proved that the 66k protein binds to the apocrine proteins carbonic anhydrase II and secretory transglutaminase and vice versa. In contrast, no binding was evident to the merocrine 115k protein and to cytoplasmic resident proteins e.g. lactate dehydrogenase. These findings point to the assumption that serum albumin taken up from extracellular sources could function as a selective carrier for cytoplasmic proteins destined for apocrine secretion.

Animals↗