Stromal development in the ventral prostate, anterior prostate and seminal vesicle of the rat

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. They produce the bulk of the seminal secretions. The object of the present study was to examine and document the ontogeny of stromal maturation in the rat anterior and ventral prostate and SV. These organs have a loosely organized cellular mesenchyme during fetal development. During prostatic development the mesenchyme condensed to form smooth muscle sheaths immediately surrounding the epithelium, with looser connective tissue between individual ducts. In the SV, a loose connective tissue layer called the lamina propria lies between the epithelium and developing muscle. Smooth muscle alpha-actin, myosin, desmin, laminin, vinculin, vimentin and androgen receptor (AR) expression were examined by immunocytochemical methods during the pre- and postnatal developmental periods. The first marker to be detected was vimentin, which was initially found throughout the mesenchyme. During development vimentin became mostly restricted to the interductal tissue of the prostate and the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proximal to distal manner along prostatic ducts, from the urethra towards the tips. Expression of alpha-actin was followed by vinculin, myosin, desmin, and laminin. These markers became localized to the developing smooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the lamina propria of the SV. Organ culture experiments demonstrated that androgens were required for the differentiation of smooth muscle sheaths. Castration of adult rats demonstrated that androgens were required to maintain smooth muscle differentiation. In castrates, the stroma was relatively thicker but less dense than in intact animals. Following castration, expression of the smooth muscle markers was lost sequentially in the reverse order of their expression during development. In long-term castrates alpha-actin, vimentin and a small amount of vinculin were detected. AR were first detected in the urogenital sinus mesenchyme immediately surrounding the epithelium at 16 days of gestation. As development progressed expression of AR became more widespread, and postnatally was found throughout the mesenchyme. As maturation of smooth muscle occurred, stromal expression of AR became localized to the muscular sheath immediately surrounding the epithelium. In the prostate the interductal connective tissue displayed very low levels of AR expression. In the SV, AR were also observed in the lamina propria. In summary, stromal differentiation and dedifferentiation in the rat prostate and SV were found to be androgen-dependent processes with ordered sequential ontogenic expression of specific markers.

Inhibition of mucin synthesis by benzyl-alpha-GalNAc in KATO III gastric cancer and Caco-2 colon cancer cells

Previous studies from our laboratory have shown that benzyl-alpha-GalNAc inhibits the glycosylation of mucin in colon cancer cells. In this study, we determined whether benzyl-alpha-GalNAc inhibits mucin glycosylation in KATO III gastric cancer cells. We also examined its effects on expression of mucin antigens, and compared the mucins made by KATO III with those of a colonic cancer cell line, Caco-2. Results of these experiments suggest that benzyl-alpha-GalNAc (2 mM) inhibited [3H]glucosamine labelling of mucins by 82% in KATO III and by 70% in Caco-2. For both cell lines, the mucin secreted in the presence of benzyl-alpha-GalNAc was less acidic. Both cell lines secreted benzyl-oligosaccharides, but those from KATO III (8-9 sugars) were larger than those from Caco-2 (6-7 sugars). In mucins purified from the medium of treated cells, peripheral carbohydrate antigens (sialyl Lex in KATO III and terminal fucose in Caco-2) were decreased (compared with control), while core carbohydrate antigens (T antigen in both cell lines and sialyl Tn in Caco-2) were increased. Western blots of cell homogenates showed differences between KATO III and Caco-2 in MUC 1 apomucin protein antigens, in sialyl Lex and in sialyl Tn antigens. We conclude that benzyl-alpha-GalNAc does inhibit the glycosylation of mucin in KATO III gastric cancer cells as in human colon cancer cells, but that alterations in mucin antigens occur in a cell line-specific manner.

Chronic penile denervation in the rat: effect on cavernous tissue morphology and function

We evaluated the effects of chronic penile denervation on cavernous tissue morphology and function in 36 Sprague-Dawley rats. At age seven weeks, 18 animals underwent bilateral cavernous nerve neurectomy: 18 animals underwent sham operation as a control. A functional, biochemical and morphological assessment of the rats' penises was performed at 4 months. In denervated rats, intracavernous pressure failed to rise with electrostimulation of the pelvic plexus. However, a normal rise in pressure was found with direct intracavernous injection of sodium nitroprusside and papaverine. Sodium dodecylsulfate polyacrylamide (SDS) gel electrophoresis of the penile homogenate showed subtle differences between denervated and control animals. Based upon the histological findings there was no difference in staining of the cavernous tissue for acetylcholinesterase- and catecholamine-positive nerve fibers between experimental and control animals, since the innervation density was not quantified and the number of fibers was not counted. We conclude that chronic cavernous nerve neurectomy does not cause significant morphological or functional changes to the penile erectile tissue of rats.

Regression of LNCaP human prostate tumor xenografts in athymic nude mice by 13-cis-retinoic acid and androgen ablation

The present study was designed to investigate the effects of 13-cis-retinoic acid (13-cis-RA) (100 micrograms/mouse/day) and androgen ablation (castration) alone and in combination on growth of a human prostatic carcinoma line (LNCaP) transplanted to athymic nude mice as an experimental model. The results of these studies suggest that; (1) androgen ablation (castration) significantly decreased the size of LNCaP xenograft as compared to untreated animals; (2) when 13-cis-RA was administered to nude mice carrying established tumors (0.51 +/- 0.04 cm3), the tumor size was significantly reduced as compared to untreated controls (0.65 +/- 0.06 cm3 versus 1.63 +/- 0.12 cm3). About 50% of the animals in this group showed xenografts necrosis followed by complete regression of tumors by five months; (3) the combination of androgen ablation and 13-cis-RA treatment to nude mice carrying tumors showed synergistic effect in decreasing the tumor size. These results indicate that combination therapies based on androgen ablation and retinoid administration may be a useful approach for the treatment of prostate cancer.

Cystic fibrosis and pancreatic cancer cells synthesize and secrete MUC1 type mucin gene product

The purpose of this study was to determine the biochemical and molecular characteristics of mucin synthesized by cystic fibrosis cells (CFPAC-1), a pancreatic cancer cell line derived from a patient with cystic fibrosis, and pancreatic cancer (SW-1990) cell lines. High molecular weight glycoproteins (HMG) were quantified by [3H]-glucosamine labeling and chromatography on sepharose CL-4B. Mucin gene expression was determined by using cDNA probes for 2 distinct intestinal mucins (MUC2 and MUC3) and one stomach mucin (MUC1). The specific mucin core epitopes were confirmed by immunoblots using antibodies that recognize T, Tn, sialosyl Tn, MUC1, MUC2, and MUC3. The results of these experiments demonstrate that CFPAC-1 cells contained 1.25 fold and 1.4 fold more HMG in the membrane and cytosolic fractions, however, secreted 4-fold more HMG into the medium compared to SW-1990 cells. The HMG of SW-1990 was found to be mucinous in nature and not proteoglycans, as it was not susceptible to hyalurinidase, heparinase and chondroitinase ABC. The HMG of CFPAC-1 was also predominantly (80%) mucinous but with small amounts of proteoglycans. mRNA and immunoblot analysis suggest that these CFPAC-1 and SW-1990 cells predominantly express MUC1 apomucin, small amounts of MUC2 apomucin, and no MUC3. Pulse chase labeling and immunoprecipitation of MUC1 type mucin using the 139H2 monoclonal antibody demonstrated that different sizes of mucin gene product were present in both cell lines, corresponding to the known length polymorphism of this mucin. Both T and Tn antigens were significantly higher in CFPAC-1 and SW-1990 cells as compared to sialosyl Tn antigen. These findings were associated with the increased activities of polypeptidyl N-acetylgalactosaminyl transferase and b1,3-galactosyltransferase. These investigations demonstrate for the first time that cystic fibrosis cells (CFPAC-1) secrete and synthesize high amounts of mucin which is associated with high levels of MUC1 mRNA, low levels of MUC2 mRNA and non detectable MUC3 mRNA.

Establishment and characterization of an immortalized but non-transformed human prostate epithelial cell line: BPH-1

This report describes the development and characterization of an epithelial cell line (BPH-1) from human prostate tissue obtained by transurethral resection. Primary epithelial cell cultures were immortalized with SV40 large T antigen. One of the isolated clones was designated BPH-1. These cells have a cobblestone appearance in monolayer culture and are non-tumorigenic in nude mice following subcutaneous injection or subrenal capsule grafting. They express the SV40 large T antigen and exhibit increased levels of p53, as determined by immunocytochemistry. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with a modal chromosome number of 76 (range 71 to 79, n = 28) and 6 to 8 marker chromosomes. Some structurally rearranged chromosomes were observed, but the Y chromosome was normal. The expressed cytokeratin profile was consistent with a prostatic luminal epithelial cell. This profile was the same as that of primary prostatic epithelial cultures from which the BPH-1 cells were derived. In serum-free culture in plastic dishes epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, fibroblast growth factor (FGF) 1 (aFGF), and FGF 7 (KGF) induced increased proliferation in these cells whereas FGF 2 (bFGF), TGF-beta 1, and TGF-beta 2 inhibited proliferative activity. Testosterone had no direct effect on the proliferative rate of BPH-1 cells. 5 alpha-Reductase, 3 alpha-hydroxysteroid oxidoreductase, and 17 beta-hydroxy-steroid oxidoreductase activities were detected in BPH-1 cells. Expression of androgen receptors and the secretory markers, prostate specific antigen and prostatic acid phosphatase, were not detectable by immunocytochemistry, biochemical assay, or RT-PCR analysis.

Equilibrium linkage analysis of cardiac thin filament assembly. Implications for the regulation of muscle contraction

A major focus in studies of muscle contraction has been the effect of Ca2+ on the interactions among the thin filament's five constituent polypeptides: actin, tropomyosin, troponin C (TnC), troponin T (TnT), and troponin I (TnI). We have investigated these interactions by analyzing thin filament assembly as a linear lattice binding problem with linkage relationships in the associations of tropomyosin, actin, and troponin. Binding of TnT, the binary TnT.TnI complex, or the ternary troponin complex (+/- Ca2+) to tropomyosin was measured spectrofluorimetrically after labeling cardiac tropomyosin with N-(1-pyrene)iodoacetamide. The affinity constants ranged between 0.2 and 0.6 microM-1 in the presence of 300 mM KCl. Also, the affinities of tropomyosin, tropomyosin-troponin, tropomyosin.TnT, and tropomyosin.TnT.TnI for an isolated site on F-actin were determined. The actin association constants were 0.0006 microM-1 for tropomyosin, 1 microM-1 for tropomyosin.TnT, 2 microM-1 for tropomyosin.TnT.TnI, 0.5 microM-1 for tropomyosin.troponin, and 0.5 microM-1 for tropomyosin-troponin.Ca2+. Linked equilibrium analysis permitted calculation of the affinities for actin.tropomyosin of TnT (400 microM-1), TnT.TnI (1600 microM-1), troponin (500 microM-1), and troponin.Ca2+ (300 microM-1). Therefore, both troponin and tropomyosin.troponin retain high actin-affinity even when Ca2+ is present or when TnI is removed, and even in the absence of cooperative contributions. The results are discussed in consideration of increasing evidence for a Ca(2+)-regulated azimuthal movement of tropomyosin on F-actin (Lehman, W., Craig, R., and Vibert, P. (1994) Nature 368, 65-67). It is proposed that tropomyosin movement may be due to switching between TnI-mediated and TnT-mediated binding of troponin-tropomyosin to distinct sites on F-actin.

Inhibition of tumorigenic potential and prostate-specific antigen expression in LNCaP human prostate cancer cell line by 13-cis-retinoic acid

Prostate-specific antigen (PSA) is a member of the kallikrein family and has been an important biological marker for prostate cancer. The mechanisms regulating PSA expression in prostatic cancer cells are unclear. The present study was designed to elucidate the role of 13-cis-retinoic acid (RA) in regulation of PSA and the tumorigenic potential of the human prostate cancer cell line LNCaP. The growth regulation of LNCaP cells was examined by DNA synthesis and doubling time. The tumorigenic potential of prostate cancer cells was analyzed by soft agar colony-forming assay, in vitro invasion assay, type IV collagenase assay and binding to extracellular matrix assay. The nuclear receptors for retinoic acid (RAR alpha, -beta, -gamma and RXR alpha, -beta, -gamma) as well as PSA mRNA were determined by Northern blot using specific oligonucleotide probes. Our results suggest that 13-cis-RA significantly inhibits PSA secretion and expression both at the mRNA and protein levels compared with untreated cells. Electron microscopic studies suggest that after 13-cis-RA treatment, cells become more differentiated as they contain lumina, lined by plasma membrane and microvilli. Prostate cancer cell growth and tumorigenic potential after 13-cis-RA treatment was significantly decreased compared with controls. Nude mice tumorigenicity studies showed that 13-cis-RA-treated cells produced significantly smaller tumors compared with untreated cell tumors. There was also a significant increase in the expression of RXRa mRNA after 13-cis-RA treatment compared with untreated cells.

Stable differentiation of a human colon adenocarcinoma cell line by sodium butyrate is associated with multidrug resistance

Colorectal cancers are often composed of cell types representing various differentiated cell lineages, however little is known concerning the relationship of differentiation and drug resistance in these cancers. The present study was performed to develop and characterize a stable, differentiated clone of the human colon cancer cell line LS174T and to characterize the drug resistance of this cell line in relation to its undifferentiated parental cell line. LS174T cell line was treated with the differentiating agent sodium butyrate (0.5 mM) for 30 days, then recultured in standard medium. Foci of flat-appearing cells appeared and were isolated using cloning rings, and subcloned. One subclone was designated LS174T-D. The LS174T-D clone maintains a stable, differentiated phenotype in standard culture conditions in the absence of sodium butyrate. It is characterized by the formation of a polarized monolayer with dome formation and the presence of prominent apical microvilli and tight junctions. This cell line demonstrated reduced growth in soft agar and nude mice compared with the parental cell line. LS174T-D cells expressed immunoreactive intestinal mucin antigens and brush border enzymes dipeptidyl aminopeptidase (DAP)-IV and aminopeptidase. The activities of DAP-IV and aminopeptidase were increased 5.6-fold and 3.4-fold, respectively, in LS174T-D compared with parental cells. Proliferation assays demonstrated that, compared with the parental cell line, LS174T-D cells were more resistant to doxorubicin (93-fold), cisplatin (23-fold), 5-fluorouracil (12-fold), 5-fluorodeoxyuridine (31-fold), and methotrexate (12.5-fold). Intracellular uptake of (3H)-5-fluorodeoxyuridine did not differ significantly in the differentiated and undifferentiated cell lines. Levels of mdr-1 p-glycoprotein measured by Western blot and RNA Northern blot assays were also similarly low in both cell lines. However, total glutathione content and glutathione-S-transferase activities were increased in LS174T-D cells by sixfold and threefold, respectively, compared with parental cells. Depletion of glutathione by pretreatment with DL-buthionine sulfoximine reversed LS174T-D resistance to cisplatin. Long-term treatment with sodium butyrate induces or selects for colon cancer cells with features of enterocytic differentiation. This stably differentiated cell line is associated with glutathione-mediated multidrug resistance, and provides a model for further studies of differentiation in normal and cancerous colon.

13-cis-retinoic acid-mediated growth inhibition of DU-145 human prostate cancer cells

The purpose of this study was to examine the effects of 13-cis-retinoic acid (13-cis-RA) on the growth regulation of DU-145 human prostatic cancer cells. The results of these experiments demonstrate that cell growth and metastatic potential of DU-145 cells were significantly inhibited by 13-cis-RA (10 microM). In order to elucidate the possible molecular mechanisms of 13-cis-RA action on prostate cancer cells, we examined the expression of nuclear receptor genes (hRXR alpha) and found that 13-cis-RA treated cells showed higher mRNA expression for hRXR alpha nuclear receptors compared to untreated cells. To elucidate further the possible biochemical mechanisms associated with these alterations, we analyzed the phosphorous metabolites by MR spectroscopy and found that the major metabolites were PME, (PC, PE) and DPDE (UDP-GalNAc, UDP-GLcNAc). The DU-145 cells and xenografts, which were both treated with 13-cis-RA, showed a two-fold decrease in DPDE's, compared to their controls. The higher resolution spectra of perfused cells revealed that phosphocholine levels were twice as high in 13-cis-RA-treated DU-145 cells as compared to untreated cells. These investigations demonstrate for the first time that 13-cis-RA inhibits the growth of human prostatic cancer cells, and this inhibition is associated with an increase in hRXR alpha nuclear receptor gene expression and alterations in phosphorous metabolites detected by 31P MR spectroscopy.

HLA expression by benign and malignant prostatic epithelium: augmentation by interferon-gamma

Chronic prostatitis is a poorly understood entity that is characterized by lymphocytic infiltration of benign prostatic epithelium. Previously, we and others have shown that prostatic epithelium involved by prostatitis is phenotypically different from uninvolved epithelium. In addition, we have shown that malignant prostatic epithelium is rarely, if ever, infiltrated by lymphocytes. We now report that benign prostatic epithelium expresses HLA-DR only in the presence of lymphocytic inflammation, and that benign epithelium without chronic prostatitis and malignant prostatic epithelium do not express HLA-DR. In order to determine whether HLA-DR expression is inducible on malignant prostatic epithelium and therefore, at least theoretically, susceptible to immune regulation, we studied the DU-145 cell line in culture under various conditions. DU-145 cells did not express HLA-DR under routine culture conditions. However, the addition of interferon-gamma (100 to 6000 U/ml.) resulted in HLA-DR expression by DU-145 cells at 24 hours with maximal expression by 72 hours. In contrast, other cytokines (tumor necrosis factor, interleukin-1, interleukin-2) had no effect on HLA-DR expression. These investigations show that interferon-gamma induces HLA-DR expression on the DU-145 prostatic adenocarcinoma cell line, raising the theoretical possibility that malignant prostatic cells may be induced in vivo to express HLA-DR and thus become susceptible to immune regulation.

Pelvic plexus denervation in rats causes morphologic and functional changes of the prostate

The effect of pelvic plexus denervation on biochemical, morphologic and functional characteristics of the rat prostate was assessed in 11 adult Sprague-Dawley rats. Unilateral denervation was performed by removing the right pelvic ganglion from the surface of the prostate; the contralateral lobe was similarly dissected, but not denervated, to serve as a control. After 15 to 18 days, the prostate was excised and specimens from both sides were used for morphologic (light and electron microscopy) and biochemical studies (sodium-dodecylsulfate-polyacrylamide gel electrophoresis). With light microscopy, histologic features of the denervated prostate showed an overall decrease in cell height and a reduction of the clear apical area of the supranuclear region. At an ultrastructural level, denervated prostatic epithelial cells showed a slight, but significant, reduction in the number of secretory granules, a decrease in the height of the supranuclear region, and fewer and less abundantly dilated apical cisternae of endoplasmic reticulum. These changes indicate a modification of the secretory activity and reflect a change in epithelial metabolism, which was further supported by the results of SDS gel electrophoresis: the denervated prostate tissue showed an increase in the expression of 108 kDa and 80 kDa protein bands and a decrease in the expression of the 45 kDa protein band. This modification in the protein content is probably temporal and would undergo further evolution with time. The finding that denervation of the prostate causes significant morphologic and functional changes of the glandular epithelium strongly suggests that prostate function is not subject solely to the regulatory influence of the hormonal milieu. It is also dependent on the anatomical and, quite possibly functional, integrity of the nervous system.

Phenotypic and cytogenetic characterization of a human corpus cavernosum cell line (DS-1)

We report here the establishment and characterization of a corpus cavernosum cell line (DS-1) from human penile tissue. This is the first cell line of its type derived from cavernosum tissue. DS-1 cells have become immortalized in culture, and show growth in monolayers. These cells have a doubling time of about 45 h in in vitro culture. Cytogenetic analysis by G-banding demonstrated a diploid karyotype with a model chromosome number of 46. The chromosome constitution of DS-1 cells was found to be male (XY), in 28/30 cells scored. Two of the 30 cells showed an extra structurally rearranged "marker" chromosome, that appeared to be a derivative of chromosome 18 with excessive chromosome on the short arm. Ploidy analysis revealed that the majority of DS-1 cells had a DNA index of one. About 35% cells were found to be in G-1 phase and 52% cells in S phase. Light and electron microscopy of DS-1 cells and original penile tissue showed typical characteristics of this tissue. Immunocytochemistry studies using antibodies to smooth muscle actin, desmin, vimentin and cytokeratin (LP34, CAM5.2) showed that the DS-1 cell line had predominantly smooth muscle cells, as these cells were positive for smooth muscle actin, desmin and vimentin.

Mucin synthesis and secretion in various human epithelial cancer cell lines that express the MUC-1 mucin gene

Previous studies have suggested that mucin gene expression is tissue-specific; however, the relationship between unique mucin gene products and the biochemical properties of mucins is unknown. The purpose of this study was to determine the biochemical and molecular characteristics of mucin synthesized by adenocarcinoma cell lines derived from breast (ZR-75-1), stomach (MGC-803), pancreas (Capan-2), and lung (Chago K-1). Mucin was quantitated by [3H]glucosamine labeling and Sepharose CL-4B chromatography. The mucinous nature of the labeled high molecular weight glycoproteins (HMG) was verified by alkaline borohydride treatment, cesium chloride density gradient ultracentrifugation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Specific mucin gene expression was determined using cDNA probes for 2 distinct intestinal mucins (MUC-2 and MUC-3) and one breast cancer mucin (MUC-1). Specific core mucin proteins were confirmed by immunoblots using antibodies that recognize MUC-1, MUC-2, and MUC-3 core peptides. These experiments demonstrate that all cell lines contained HMG in the medium, cytosol, and membrane fractions. The HMG was mucinous in breast, pancreatic, and lung cell lines. In contrast, most of the HMG secreted by the gastric cell line was proteoglycan-like, due to its susceptibility to hyaluronidase, heparinase, and chondroitinase avidin-biotin complex. Ion-exchange (DEAE-Sephacel) chromatography of [3H]glucosamine-labeled HMG demonstrated that the acidic or basic nature of the mucin was different in all cancer cell lines tested. Despite these differences, mRNA and immunoblot analysis suggest that all cell lines predominantly express MUC-1 apomucin, small amounts of MUC-2 apomucin, and no MUC-3. Immunoprecipitation of MUC-1-type mucin using the 139H2 monoclonal antibody demonstrated that different sizes of mucin peptides were present in all cell lines, corresponding to the known length polymorphism of this mucin. The amount and nature of carbohydrate epitopes were analyzed by immunoblots using anti-T (peanut lectin), anti-Tn (91S8 monoclonal antibody), and anti-sialosyl Tn (JT10e monoclonal antibody). T and Tn antigens were significantly higher in breast and pancreatic cells as compared with lung and gastric cell lines. These findings correlated with increased activities of polypeptidyl N-acetylgalactosaminyl transferase and beta-1,3-galactosyltransferase.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of glucose and confluency on phosphorus metabolites of perfused human prostatic adenocarcinoma cells as determined by 31P MRS

A series of perfused cell 31P MRS studies were conducted using a well established human prostate adenocarcinoma cell line (DU 145) at different phases of growth, and exposed to varying glucose concentrations during growth. The spectral characteristics of perfused DU 145 cells were compared with the same cells grown in nude mice (xenografts). Perfused DU 145 cells had lower levels of inorganic phosphate and phosphocreative relative to in vivo nude mice xenografts. 31P MR spectra obtained from perfused cells at different phases of growth and exposed to varying glucose concentrations during grown suggest that increases in diphosphodiester levels are associated with high glucose concentrations and confluency. Perfused DU 145 cells grown in 5.5 mM glucose and harvested at log phase of growth best reflected the phosphorus MR spectra of the same cell line grown in nude mice.

Citrate alterations in primary and metastatic human prostatic adenocarcinomas: 1H magnetic resonance spectroscopy and biochemical study

The objectives of this study were to quantitatively verify the low levels of citrate previously observed in primary human prostatic adenocarcinomas and to determine whether citrate was further reduced in metastatic prostatic cancer. This was accomplished by comparison of citrate concentrations of DU 145 xenografts (a poorly differentiated human prostatic adenocarcinoma cell line grown in nude mice) with concentrations in primary human adenocarcinomas. Following in vivo 1H NMR studies of DU 145 xenografts, citrate concentrations of DU 145 xenografts and surgically removed primary prostatic adenocarcinoma tissue were determined by quantitative high resolution 1H NMR and enzymatic assay. The most significant findings of this study were that citrate concentrations in primary human adenocarcinomas (3.74 +/- 0.19 mumol/g wet weight) were significantly lower than those observed for normal and benign hyperplastic (BPH) prostatic tissues. Furthermore there was a further ten-fold reduction of citrate associated with DU 145 xenografts (0.31 +/- 0.028 mumole/g wet weight) compared with primary prostatic cancer. DU 145 xenografts also exhibited higher levels of uridine diphosphosugars and choline containing metabolites relative to primary prostatic adenocarcinomas. These findings support the hypothesis that citrate is low in primary prostatic cancer and further reduced in metastatic disease.

Heterogeneity of mucin gene expression in normal and neoplastic tissues

To determine the relative expression of distinct mucin genes in normal and neoplastic tissue, antibodies and cDNA probes that recognize the core tandem repeat sequences of membrane-bound (MUC1) and secreted (MUC2 and MUC3) mucins were used for immunohistochemical and RNA Northern and slot-blot analysis. MUC1 mRNA was detected in all epithelial tissues tested. MUC1 core peptide, recognized by monoclonal antibodies 139H2 and DF3, was highly expressed on apical membranes of bronchus, breast, salivary gland, pancreas, prostate, and uterus, and was sparsely expressed in gastric surface cells, gallbladder, small intestine, and colonic epithelium. In contrast, MUC2 and MUC3 gene expression was primarily restricted to the intestinal tract. MUC2 mRNA was highly expressed in normal jejunum, ileum, and colon, compared with very low levels in normal bronchus and gallbladder. MUC3 mRNA was highly expressed in normal jejunum, ileum, colon, and gallbladder. Immunohistochemical studies using antibodies against synthetic MUC2 (anti-MRP) and MUC3 (anti-M3P) peptides indicate that MUC2- and MUC3-producing cells in the gastrointestinal tract are distinct. Goblet cells of the small intestine and colon reacted strongly with anti-MRP, whereas M3P reactivity was restricted to columnar cells of small intestinal villi, surface colonic epithelium, and gallbladder. Mucin protein epitopes and mRNA levels were frequently altered in adenocarcinomas compared to corresponding normal tissues. Alterations included increased expression, aberrant expression, and, less frequently, loss of expression. Increased MUC1 immunoreactivity was observed in most adenocarcinomas of the breast, lung, stomach, pancreas, prostate, and ovary. In addition, with the exception of prostate cancer, focal aberrant expression of MUC2 and MUC3 epitopes was frequently observed. Increased MUC1, MUC2, and MUC3 epitopes were present in colon adenocarcinomas of all histological subtypes, with the greatest increase of MUC2 epitopes observed in colloid (mucinous) colon cancers. MUC2 or MUC3 mRNA levels were increased in colloid colon cancer compared with normal colon, however in well- and moderately well-differentiated colon cancers MUC1, 2 and 3 mRNA levels were decreased. Compared with corresponding normal tissue, MUC1 mRNA levels were increased in breast cancer and well-differentiated lung cancers, and MUC3 mRNA was increased in gastric adenocarcinomas. Normal stomach lacked both MUC2 and MUC3 immunoreactivity and mRNA, however, MUC2 and MUC3 proteins and mRNA were highly expressed in gastric intestinal metaplasia. In conclusion, mucin genes are independently regulated and their expression is organ- and cell type-specific. Furthermore, neoplastic transformation is associated with dys-regulated expression of both membrane-bound and secreted mucin core protein epitopes and may be due to altered mucin mRNA levels and/or altered mucin glycosylation.

Sodium nitroprusside and neurostimulation cause increased levels of cyclic guanosine monophosphate and not cyclic adenosine monophosphate during canine penile erection

We investigated the changes of cGMP and cAMP during penile erection induced by direct electrical stimulation of the pelvic nerve or sodium nitroprusside administration. Immediately after penile erection, the samples were put into liquid nitrogen and cyclic nucleotide content was measured. The results of these investigation suggest that both pelvic nerve stimulation and sodium nitroprusside induced penile tumescence. The total content of cGMP and not cAMP were significantly higher in treated samples as compared to control. SDS-polyacrylamide gel electrophoresis revealed several differences after treatment compared to untreated samples. This study demonstrated that the total content of cGMP and not cAMP increased after pelvic nerve stimulation and sodium nitroprusside treatment in penile tissue.

Downregulation of saturated fatty acid and upregulation of unsaturated fatty acid by 13-cis-retinoic acid in human prostate cancer cells

Retinoids play a major role in regulation of epithelial cell growth and cellular differentiation, but their mechanism(s) of action are still unclear. In the present study, we examined the effects of 13-cis-retinoic acid (13-cis-RA) on cytotoxicity, growth properties, morphology, neutral lipids, phospholipids and fatty acids in cultured human prostate cancer cell lines. The results of these experiments suggest that 13-cis-RA (10 microM) inhibits the DNA synthesis and nude mice tumorigenicity by 2- to 3-fold, compared to control. Electron microscopy revealed more differentiated phenotypes after 13-cis-RA treatment. There was a significant increase in phosphatidylcholine and decrease in sphingomyelin in 13-cis-RA treated cells compared to control. The saturated fatty acids significantly decreased whereas unsaturated fatty acids were increased after 13-cis-RA treatment in prostate cancer cells. This study demonstrates for the first time that retinoic acid mediated downregulation of saturated fatty acids and upregulation of unsaturated fatty acid in human prostate cancer cells.

Establishment and characterization of a human primary prostatic adenocarcinoma cell line (ND-1)

A human primary prostatic adenocarcinoma cell line named ND-1 has been established in long term tissue culture. The cultured cells show growth in both monolayers and in soft agar suspension and produce subcutaneous tumors in nude mice. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with a modal chromosome number of 62, and multiple marker chromosomes with 25-30% structural abnormalities. Ploidy analysis revealed that the majority of ND-1 cells (67%) had a DNA mass of 10.1 picogram and DNA index of 1.41. Nineteen percent of cells had a DNA mass of 21.3 picogram and DNA index of 3.0. Electron microscopic studies revealed common features of neoplastic epithelial cells such as numerous microvilli, junctional complexes, abnormal nuclei, nucleoli, and mitochondria. Due to the absence of a structurally normal Y chromosome, confirmation of the presence of a derived Y chromosome was achieved through the use of C-banding and through fluorescent in situ hybridization with a Y chromosome repeat probe. Tandem E PSA immunoenzymatic assay revealed that these ND-1 cells secrete small amounts of prostate specific antigen.

Mucin oligosaccharide biosynthesis in human colonic cancerous tissues and cell lines

BACKGROUND

The Tn, sialosyl-Tn, and T antigens are carbohydrate-associated antigens that represent initial steps in mucin O-linked glycosylation. Previous immunohistochemical studies have shown that these three antigens are rarely, if ever, expressed in normal colonic mucosa; however, most colonic cancerous tissues express these structures. Little is known about the factors that control the expression of these antigens in colonic tissues or cell lines. One hypothesis is that cancers have increased levels of the glycosyltransferase activities responsible for synthesizing these antigens.

METHODS

The current study analyzed antigen expression by immunohistochemistry and glycosyltransferase enzyme activities for Tn, sialosyl-Tn, and T antigens in colonic tissues and cell lines to (1) compare values between normal and cancerous tissues and (2) correlate these results with tumor stage, histologic findings, and location.

RESULTS

All nine colonic cancer cell lines expressed Tn antigen; sialosyl-Tn and T antigens were expressed by the more mucin-producing cell lines. Sialosyl-Tn transferase activity was higher in the more mucinous cell lines; T transferase activity was higher in those with less mucin. In paired specimens of normal and cancerous tissues, levels of each of the three glycosyltransferases were similar. In cancerous tissues, enzyme activity did not correlate with tumor location, stage, or histologic type. There also was no correlation between glycosyltransferase activity and expression of the relevant antigen.

CONCLUSIONS

Thus, because normal and malignant colonic tissues have comparable levels of Tn, sialosyl-Tn, and T glycosyltransferases, the absence of these antigens in normal mucosa apparently is related to other factors such as antigen masking.

Expression and characterization of mucins associated with the resistance to methotrexate of human colonic adenocarcinoma cell line HT29

A series of experiments were conducted to study synthesis and secretion of mucin in mucus-secreting subpopulations of HT29 human colonic adenocarcinoma cells selected by resistance to methotrexate (MTX). Mucin was quantitated by [3H]glucosamine labeling and chromatography on Sepharose CL-4B. The mucinous nature of the labeled high molecular weight glycoprotein was verified by alkaline borohydride treatment, cesium chloride density gradient ultracentrifugation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results of these experiments demonstrated that MTX-treated cells have increased amounts of mucin in medium, cytosol, and membrane fractions. This was associated with the increase in the activities of polypeptidyl-N-acetylgalactosaminyltransferase and beta-1,3-galactosyltransferase compared to control cells. DEAE-Sephacel chromatography of [3H]glucosamine-labeled high molecular weight glycoproteins suggest that MTX-treated cells are less acidic compared to controls. Using complementary DNA probes for two distinct human intestinal mucins (MUC2 and MUC3) and one mammary mucin (MUC1), it was found that MTX-treated cells expressed more mucin messages compared to untreated cells. These results were consistent with immunoblots using anti-MRP (MUC2 repeat peptide), anti-M3P (MUC3 repeat peptide), 139H2 (MUC1 peptide), anti-T (peanut lectin), anti-Tn (91S8), and anti-sialosyl Tn (JT10e) antibodies. These data indicate that MTX-resistant HT29 cells show enhanced secretion and synthesis of mucin as well as expression of MUC1-, MUC2-, and MUC3-related mucin polypeptide epitopes.

Biochemical, cytogenetic, and morphological characteristics of human primary and metastatic prostate cancer cell lines

Metastatic properties of human prostatic cancer cell lines (ND-1 and DU-145) were examined using various biochemical techniques. DU-145 cells had a higher metastatic potential than ND-1 cells. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with considerable structural rearrangement. ND-1 cells had a modal chromosome number range lower than DU-145 cells (45-66, compared to 54-62). Ploidy analysis revealed that DU-145 cells showed hyperdiploidy with a greater amount of proliferation than the majority of ND-1 cells. Electron microscopic studies revealed little change in the cell morphology of either line. DU-145 cells had lower phosphatidyl choline levels and higher sphingomyelin levels than ND-1. DU-145 cells had much lower arachidonic acid levels than ND-1 cells. SDS-polyacrylamide gel electrophoresis revealed protein differences between the two cell lines. This study demonstrates for the first time that lipids, proteins and cytogenetic parameters differ in human primary and secondary prostate cancer cell lines.

Metastasis-associated alterations in phospholipids and fatty acids of human prostatic adenocarcinoma cell lines

Metastatic variants of human prostatic adenocarcinoma cell lines (DU-145, LNCaP, and ND-1) were studied by using soft agar colony forming efficiency, nude mice tumorigenicity, in vitro invasion assay, and type IV collagenase assay. The DU-145 and ND-1 cell line showed higher metastatic potential than LNCaP. Lipids from DU-145, ND-1, and LNCaP cells were extracted and analyzed by thin-layer chromatography and gas-liquid chromatography. The major lipids were phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, fatty acids, and cholesterol. The sphingomyelin level was significantly higher in highly metastatic cells (DU-145 and ND-1) compared with the lower metastatic variant (LNCaP). The increase in the synthetic pathway and decrease in degradation pathway of sphingomyelin in microsomal fractions was sufficient to account for the measured increase in sphingomyelin in DU-145 cells compared with LNCaP cells. The major fatty acids of these lipids were palmitic (16:0), stearic (18:0), oelic (18:1), and arachidonic acid (20:4). The arachidonic acid level was significantly decreased in DU-145 and ND-1 compared with LNCaP cells. Electron microscopic studies showed no significant changes in the morphology of DU-145, ND-1, and LNCaP cells. The results of these investigations demonstrate for the first time that sphingomyelin and arachidonic acid contents are different in high and low metastatic variants of human prostatic adenocarcinoma cell lines.

Mucin synthesis and secretion in relation to spontaneous differentiation of colon cancer cells in vitro

The synthesis and secretion of mucin-like high-molecular glycoprotein was studied in 2 human colon cancer cell lines that spontaneously differentiate in culture (Caco-2 and T84) and in 2 cell lines that do not spontaneously differentiate (LS174T and HT29). Mucin, quantitated by 3H-glucosamine labelling and chromatography on Sepharose CL-4B was found to be produced by all 4 cell lines. The mucinous nature of the labelled high-molecular glycoprotein was verified by enzymatic degradation treatments (heparinase, hyaluronidase, chondroitinase ABC, and N-glycanase), alkaline-borohydride treatment, inhibition of labelling by the glycosylation inhibitor benzyl-alpha-GalNAc, and by CsCl-density-gradient centrifugation. In all 4 cell lines, an inverse correlation of mucin synthesis with cell density was demonstrated. In Caco-2 cells, the spontaneous post-confluent enterocytic differentiation with increased brush-border enzyme expression was associated with a decrease in mucin synthesis and in the activities of polypeptidyl GalNAc transferase and beta 1,3-galactosyltransferase activity. Using cDNA probes for 2 distinct human intestinal mucins (MUC2 and MUC3), we found that all 4 colon cancer cell lines expressed mucin message, but the types of mucin mRNA expressed differed. These data indicate that mucin-like glycoproteins can be synthesized by cell lines derived from non-mucinous colon cancer, whether or not they undergo spontaneous differentiation in culture. These cell lines may serve as in vitro models for studying apomucin heterogeneity and control of mucin gene expression.

Differential mucin gene expression in human pancreatic and colon cancer cells

The purpose of this study was to determine the quantity and nature of the mucins synthesized and secreted by four different pancreatic cancer cell lines. Well- to moderately-differentiated SW1990 and CAPAN-2 human pancreatic cancer cells were found to produce more high-Mr glycoprotein (HMG) than less-differentiated MIA PaCa-2 and PANC-1 cells. Most of the labelled HMG was secreted within 24 h. The results of chemical and enzymic degradation, ion-exchange chromatography and density-gradient centrifugation indicated that the HMG in SW1990 and CAPAN-2 cells has the properties expected for mucins, whereas much of the HMG in MIA PaCa-2 and PANC-1 cells may not be mucin, but proteoglycan. These results are consistent with immunoblots and Northern blots showing the presence of apomucin and apomucin mRNA in SW1990 and CAPAN-2 cells, but not in MIA PaCa-2 and PANC-1 cells. The Western blots and Northern blots also show that SW1990 and CAPAN-2 cells, like breast cancer cells, have the mammary-type apomucin and mRNA coded by the MUC1 gene, but lack the intestinal type apomucin and mRNA coded by the MUC2 gene. In contrast, the colon cancer cell lines tested in culture express apomucin and mRNA coded by MUC2 but not by MUC1.

Mucin production by human colonic carcinoma cells correlates with their metastatic potential in animal models of colon cancer metastasis

Patients with mucinous colorectal cancers characteristically present with advanced disease, however, the relationship between mucin production by colon cancer cells and their metastatic potential remains unclear. We therefore sought to define the relationship between mucin production by human colon cancer cells and metastatic ability by employing animal models of colon cancer metastasis. LS LiM 6, a colon carcinoma cell line with high liver metastasizing ability during cecal growth in nude mice produced twofold more metabolically labeled intracellular mucin and secreted four- to fivefold more mucin into the culture medium compared to poorly metastatic parental line LS174T. This was accompanied by a similar elevation in poly(A)+ RNA detected by blot hybridization with a human intestinal mucin cDNA probe, and increases in mucin core carbohydrate antigens determined immunohistochemically. Variants of LS174T selected for high (HM 7) or low (LM 12) mucin synthesizing capacity also yielded metastases after cecal growth and colonized the liver after splenic-portal injection in proportion to their ability to produce mucin. Inhibition of mucin glycosylation by the arylglycoside benzyl-alpha-N-acetyl-galactosamine greatly reduced liver colonization after splenic-portal injection of the tumor cells. These data suggest that mucin production by human colon cancer cells correlates with their metastatic potential and affects their ability to colonize the liver in experimental model systems.

Blood group antigen synthesis and degradation in normal and cancerous colonic tissues

ABH antigens are expressed by colonic epithelial cells throughout the colon during fetal life but only in proximal segments during adulthood. Malignant and premalignant colonic tumors frequently exhibit ABH reappearance (distal lesions) or ABH deletion (proximal lesions) and occasionally express incompatible A or B substances. Mechanisms governing these developmental and cancer-associated alterations are unknown. Therefore, experiments were performed to assess the activities of biosynthetic (glycosyltransferase) and degradative (glycosidase) enzymes in normal and cancerous tissues of the proximal and distal colon. In normal colonic mucosa, A, B, and H transferase activities were similar in proximal and distal segments. Analysis of enzyme substrate affinities and product characterization confirmed that the ABH transferases in colonic tissues were similar to the gene-specified transferases in human serum. Glycosidase enzyme activities were also comparable in proximal and distal normal colon. Cancers had lower A and B transferase but similar H transferase activities compared with paired normal mucosa. Thus, the absence of ABH antigen expression in normal distal colon is not caused by insufficient glycosyltransferase activity or excessive glycosidase activity.

Inhibition of lipoprotein lipase activity by high density lipoprotein & apolipoproteins C, E & A in rhesus monkeys

Experiments were conducted to study the effects of high density lipoprotein (HDL) and apolipoproteins C, E, and A on lipoprotein lipase activity in rhesus monkeys. The lipoprotein lipase activity was inhibited up to 32 +/- 6 per cent by monkey HDL. This inhibition was considerably decreased (2 +/- 0.02%) by using apolipoprotein-poor HDL. Apolipoproteins C and E inhibited the hydrolysis of activated intralipid by monkey lipoprotein lipase to a maximum of 83 +/- 7 and 57 +/- 5 per cent respectively. Apolipoprotein A produced little inhibition of lipoprotein lipase activity. The results of these studies demonstrate that HDL and apolipoproteins compete with the substrate for the binding to lipoprotein lipase in rhesus monkeys.

Cell surface sialoprotein alterations in metastatic murine colon cancer cell lines selected in an animal model for colon cancer metastasis

Alterations in cell surface proteins and glycoproteins may play a key role in determining the metastatic behavior of tumor cells. The cell surface proteins of a series of related murine colon cancer cells selected in an animal model for colon cancer metastasis (R. S. Bresalier et al., Cancer Res., 47: 1398-1406, 1987) were therefore compared by a variety of biochemical methods. Lactoperoxidase-catalyzed iodination of cell surface proteins followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated quantitative and qualitative differences in the cell surface protein profiles of parental cell line 51B (low metastatic potential) and its metastatic derivatives 51B LiM 5 and 51B LiM 6. Labeling of sialic acid-containing proteins suggested that, in the case of at least four of these proteins (Mr 170,000, 120,000, 95,000, and 55,000), this represented an increase in radioactive labeling of sialoglycoproteins from the metastatic lines. Affinity chromatography of solubilized 125I-labeled cell membrane proteins revealed a 2- to 3-fold increase in wheat germ agglutinin and Sambucus nigra lectin binding associated with the metastatic lines, compared to the poorly metastatic parent. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of material eluted from these columns demonstrated enhancement of proteins from the metastatic cells corresponding in molecular weight to the previously identified major sialoglycoproteins. Neuraminidase-releasable membrane-associated sialic acid and sialyltransferase activities were 2- to 3-fold higher in the metastatic cell lines compared to the parental line. Liver colonization after intrasplenic injection of the various lines into syngeneic mice was dramatically reduced by prior removal of cell surface sialic acid. Immunohistochemical staining of primary and metastatic tumors formed after cecal injection of parental 51B suggested selective metastasis by wheat germ agglutinin-binding tumor cells. These results further support the concept that cell membrane sialylation is important in determining the metastatic potential of cancer cells.

ABH blood group antigen expression, synthesis, and degradation in human colonic adenocarcinoma cell lines

The synthesis of blood group ABH antigens is under genetic control, where the primary gene products are glycosyltransferases. Several studies have demonstrated cancer-associated alterations in ABH antigen expression in human colon cancer tissues. However, the mechanism(s) responsible for these alterations has not been elucidated. Therefore, experiments were conducted using nine established colon cancer cell lines (four type O, three type A, and two type B) to examine ABH antigen expression by immunocytochemistry and correlate this with activities of ABH biosynthetic (glycosyltransferase) and degradative (glycosidase) enzymes. The products of the glycosyltransferase enzymes were characterized by high performance liquid chromatography and paper chromatography, and substrate affinities (apparent Km values) of the cancer cell-derived glycosyltransferases were analyzed. The present data demonstrate: (a) all cell lines except H-498 (blood type A) expressed the appropriate ABH glycosyltransferase as well as all three glycosidases; (b) product characterization and substrate dependence experiments suggested that the cancer cell-derived ABH glycosyltransferase enzymes had properties that were similar to those of the ABH enzymes in human serum; (c) H-498 cells exhibited A antigen deletion with accumulation of H precursor substance, most likely due to insufficient A transferase activity; (d) SW1417 cells (blood type B) demonstrated B antigen deletion without precursor accumulation, despite adequate levels of B transferase and low alpha-galactosidase activity; and (e) weak incompatible A antigen expression occurred in LoVo (type B) and SW1116 (type O) cells, and weak incompatible B antigen expression occurred in H-498 (type A) and SW1116 cells. However, since these cells lacked incompatible A or B transferase activity, these incompatible antigens are probably not the true A or B antigens. Thus, the colon cancer cell lines used in this study exhibit all of the ABH alterations previously described in colon cancer tissues and appear to be useful experimental models for studying the molecular events involved in cancer-associated ABH expression.

Basic fibroblast growth factor does not initiate mitogenic signalling via phosphoinositide hydrolysis in PC12 cells

Basic fibroblast growth factor (b FGF) was found to be equally potent mitogen as compared to alpha-thrombin to reinitiate DNA synthesis in quiescent PC12 cells. Whereas thrombin was found to be an activator of phospholipase C as judged by a rapid increase in the formation of inositol triphosphate, inositol biphosphate and a massive accumulation of inositol phosphate when 20 mM LiCl was present as an inhibitor of inositol mono phosphatases, basic FGF failed to induce the breakdown of the polyphosphoinositides in quiescent PC12 cells to any appreciable levels, however, a simultaneous increase in the level of diacylglycerol was observed. b FGF also failed to stimulate protein kinase C which is believed to be activated by diacylglycerol. It is therefore concluded that bFGF receptor mediated 'signalling is not via phospholipase C activation and bFGF's early mitogenic responses and DNA synthesis are initiated independent of the inositol lipids and protein kinase C activation. Thus bFGF must have its own unique signal transducing mechanism independent of inositol pathways.

The glycosphingolipid composition and glycosyltransferase activities of the small intestinal mucosa of testosterone-treated rats

Prior studies have demonstrated that sex hormones can influence the glycosphingolipid composition of different organs, including small intestine. However, to date, the effects of testosterone on glycosphingolipids of rat small intestinal mucosa have not been examined. Experiments were conducted to examine the effect of subcutaneous administration of synthetic testosterone (500 micrograms/100 g body wt.) on the gangliosides and neutral glycosphingolipids of rat small intestinal mucosa. Their results demonstrated that testosterone administrations: (i) increased the ganglioside content including hematoside (GM3); (ii) increased the total content of neutral glycosphingolipids, which was due to the increases in glucosylceramide and globotriaosylceramide; (iii) increased the activities of cytidine 5'-monophosphate-N-acetylneuraminic acid: lactosylceramide sialyltransferase, and UDPgalactose: lactosylceramide galactosyltransferase; (iv) increased the percentage of the long chain base phytosphingosine in hematoside, glucosyl-, and globotriaosylceramide; and (v) significantly altered the fatty acid composition of each of these glycosphingolipids. These results demonstrate that administration of testosterone induces alterations in glycosphingolipid composition and glycosyltransferases activities in rat small intestinal mucosa.

The lipid composition of plasma membrane from goat mammary gland

Experiments were conducted to examine and characterize the lipid composition of the plasma membrane from the lactating goat mammary gland. The plasma membranes were purified by discontinuous sucrose density centrifugation. Lipids were extracted from these membranes and analyzed by thin-layer and gas-liquid chromatography. The results of these studies demonstrate that (i) the principal phospholipids of mammary-gland plasma membranes are phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin; (ii) the principal neutral lipids are triacylglyceride and cholesterol ester; (iii) the major glycolipids are globotetraosylceramide and globotriaosylceramide; and (iv) the major fatty acids are oleic (18:1), palmitic (16:0), stearic (18:0), and myristic (14:0) acids.

Estrogen-induced alterations of the acidic and neutral glycosphingolipids of rat kidney

In order to determine whether female sex hormones could influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day) or vehicle for 5 days, and the ganglioside, ceramide and neutral glycosphingolipid compositions of the kidneys of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen treatment: (1) increased the ceramide, acidic and neutral glycosphingolipid contents of this tissue; (2) decreased the relative percentages of glucosyl- and globotetraosylceramide and hematoside (GM3), but increased the relative percentage of globotriaosylceramide and 'other' gangliosides; (3) increased the relative percentage of N-acetyl- to N-glycolylneuraminic acid in GM3; and (4) altered the long-chain bases of GM3, glucosyl- and globotetraosylceramide in this organ. These data, therefore, demonstrate that estrogen administration induces quantitative and qualitative alterations in the gangliosides, neutral glycosphingolipids and ceramide of the rat kidney. This data as well as a discussion of the possible physiological consequences of these estrogen-induced alterations in kidney glycosphingolipids serve as the basis for this report.

Dexamethasone-induced alterations in the glycosphingolipids of rat kidney

To determine whether glucocorticoids would influence the glycosphingolipid composition of the rat kidney, male albino rats of the Sherman strain were subcutaneously administered dexamethasone (100 micrograms/100 g body wt/day) or diluent for four days. The compositions of ceramide and of acidic and neutral glycosphingolipids of the kidneys of these animals were then examined and compared. The results demonstrated that dexamethasone administration: 1) increased the content of ceramide and of acidic and neutral glycosphingolipids in kidney; 2) increased the relative percentage of globotriaosyl- and globotetraosyl-ceramide, but decreased the relative percentages of glucosylceramide; 3) decreased the relative percentages of GM3 and increased other gangliosides; 4) increased the relative percentages of N-glycolylneuraminic acid in GM3; 5) did not appear to influence significantly the long-chain bases of the major glycosphingolipids; and 6) altered the relative percentages and chain length of the hydroxy and nonhydroxy fatty acids of the major acidic and neutral glycosphingolipids in this tissue. The data show that dexamethasone administration induces quantitative and qualitative changes in the glycosphingolipids of the rat kidney.

Dexamethasone influences the lipid fluidity, lipid composition and glycosphingolipid glycosyltransferase activities of rat proximal-small-intestinal Golgi membranes

Experiments were performed to examine the effects of subcutaneous administration of the synthetic glucocorticoid dexamethasone (100 micrograms/day per 100 g body wt.) on the lipid fluidity, lipid composition and glycosphingolipid glycosyltransferase activities of rat proximal-small-intestinal Golgi membranes. After 4 days of treatment, Golgi membranes and liposomes prepared from treated rats were found to possess a greater fluidity than their control (diluent or 0.9% NaCl) counterpart, as assessed by steady-state fluorescence-polarization techniques using three different fluorophores. Moreover, analysis of the effects of temperature on the anisotropy values of 1,6-diphenylhexa-1,3,5-triene, using Arrhenius plots, demonstrated that the mean break-point temperatures of treated preparations were 4-5 degrees C lower than those of control preparations. Changes in the fatty acyl saturation index and double-bond index of treated membranes, secondary to alterations in stearic acid, linoleic acid and arachidonic acid, at least in part, appeared to be responsible for the differences in fluidity noted between treated and control Golgi membranes. Concomitant with these fluidity and lipid-compositional alterations, treated membranes possessed higher specific activities of UDP-galactosyl-lactosylceramide galactosyltransferase and CMP-N-acetylneuraminic acid:lactosylceramide sialyltransferase than their control counterparts. Experiments utilizing benzyl alcohol, a known fluidizer, furthermore suggested that the fluidity alteration induced by dexamethasone may be responsible for the increased activity of the former, but not the latter, glycosphingolipid glycosyltransferase.

Cholesterol modulates alkaline phosphatase activity of rat intestinal microvillus membranes

Experiments were conducted, using a nonspecific lipid transfer protein, to vary the cholesterol/phospholipid molar ratio of rat proximal small intestinal microvillus membranes in order to assess the possible role of cholesterol in modulating enzymatic activities of this plasma membrane. Cholesterol/phospholipid molar ratios from 0.71 to 1.30 were produced from a normal value of 1.05 by incubation with the transfer protein and an excess of either phosphatidylcholine or cholesterol/phosphatidylcholine liposomes for 60 min at 37 degrees C. Cholesterol loading or depletion of the membranes was accompanied by a decrease or increase, respectively, in their lipid fluidity, as assessed by steady-state fluorescence polarization techniques using the lipid-soluble fluorophore 1,6-diphenyl-1,3,5-hexatriene. Increasing the cholesterol/phospholipid molar ratio also decreased alkaline phosphatase specific activity by approximately 20-30%, whereas decreasing this ratio increased this enzymatic activity by 20-30%. Sucrase, maltase, and lactase specific activities were not affected in these same preparations. Since the changes in alkaline phosphatase activity could be secondary to alterations in fluidity, cholesterol, or both, additional experiments were performed using benzyl alcohol, a known fluidizer. Benzyl alcohol (25 mM) restored the fluidity of cholesterol-enriched preparations to control levels, did not change the cholesterol/phospholipid molar ratio, and failed to alter alkaline phosphatase activity. These findings, therefore, indicate that alterations in the cholesterol content and cholesterol/phospholipid molar ratio of microvillus membranes can modulate alkaline phosphatase but not sucrase, maltase, or lactase activities. Moreover, membrane fluidity does not appear to be an important physiological regulator of these enzymatic activities.

Premalignant alterations in the glycosphingolipids of small intestinal mucosa of rats treated with 1,2-dimethylhydrazine

1,2-Dimethylhydrazine is a procarcinogen with selectivity for the colon and proximal small intestine. In weekly subcutaneous (s.c.) doses of 20 mg/kg body weight, this agent produces colonic and proximal small intestinal tumors in a high percentage of rodents with a latency period of approximately six months. To determine whether alterations in the glycosphingolipid content of rat proximal and/or distal small intestinal mucosa existed before the development of dimethylhydrazine-induced cancer, rat were given s.c. injections of this agent (20 mg/kg body weight per wk) or diluent for five wk. Animals were killed at this time, and mucosa was isolated from each small intestinal segment of both groups. Glycosphingolipids then were extracted from these tissues and analyzed by high performance thin layer chromatography and gas liquid chromatography. The results of these studies demonstrated that (1) the content of neutral and acidic glycosphingolipids was significantly decreased (approximately 20%) in the proximal small intestine of treated rats compared with their control counterparts; (2) no significant difference in the glycosphingolipid content was seen, however, in the distal small intestinal mucosa of control and treated rats; and (3) while significant differences were noted in the majority of fatty acids of GM3, glucosyl- and globotriaosylceramide in the proximal small intestine of control and treated animals, differences in the fatty acids of these glycosphingolipids in the distal segment of these groups were confined to stearic (18:0) acid and/or arachidic (20:0) acid.

Rat proximal small intestinal Golgi membranes: lipid composition and fluidity

The present studies were conducted to examine and characterize the lipid composition and physical state of the membrane lipids of rat proximal small intestinal Golgi membranes. Golgi membranes were purified from isolated enterocytes; lipids were extracted from these membranes and analyzed by thin-layer and gas-liquid chromatography. The 'static' and 'dynamic' components of fluidity of Golgi membranes and their liposomes were assessed by steady-state fluorescence polarization techniques utilizing r infinity and S values of 1,6-diphenyl-1,3,5-hexatriene and r values of DL-2-(9-anthroyl)- and DL-12-(9-anthroyl)stearic acid, respectively. Additional studies were also performed on these membranes, using benzyl and methyl alcohol, to examine the relationship between alterations in lipid fluidity and glycosphingolipid glycosyltransferase activities. The results of these studies demonstrated that: (1) the principal phospholipids and neutral lipids of intestinal Golgi membranes, respectively, were phosphatidylcholine, phosphatidylethanolamine and sphingomyelin, and unesterified cholesterol and fatty acids; (2) the major fatty acids of Golgi membranes were palmitic (16:0), stearic (18:0), linoleic (18:2), arachidonic (20:4) and oleic (18:1) acids; (3) fluorescence polarization studies using diphenylhexatriene detected a thermotropic transition at 24-26 degrees C in Golgi membranes and liposomes prepared from lipid extracts of these membranes; (4) benzyl alcohol (25 and 50 mM) but not methyl alcohol (50 mM) significantly increased the fluidity of these membranes; and (5) at these same concentrations, benzyl alcohol was also found to increase significantly the specific activity of UDP-galactosyllactosylceramide galactosyltransferase but not CMP-acetylneuraminic acid: lactosylceramide sialyltransferase. Methyl alcohol was not found to influence either enzyme's activity in these membranes.

Dexamethasone-induced alterations in lipid composition and fluidity of rat proximal-small-intestinal brush-border membranes

A series of experiments were conducted to examine the possible effects of subcutaneous administration of the synthetic glucocorticoid dexamethasone (100 micrograms/day per 100 g body wt.) on the lipid fluidity and lipid composition of rat proximal-small-intestinal brush-border membranes. After 4 days of treatment, membranes and their liposomes prepared from treated animals possessed a greater fluidity than did their control (diluent, 0.9% NaCl) counterparts, as assessed by steady-state fluorescence-polarization techniques using several different fluorophores. Examination of the effects of temperature on the anisotropy values of 1,6-diphenylhexa-1,3,5-triene, using Arrhenius plots, moreover, revealed that the mean break-point temperatures of the treated preparations were approx. 3-4 degrees C lower than those of their control-preparation counterparts. Changes in the sphingomyelin/phosphatidylcholine (PC) molar ratio as well as in certain of the fatty acids of the PC fraction of treated membranes, secondary to alterations in membrane PC levels and in lysophosphatidylcholine acyltransferase activities respectively, were also noted after dexamethasone administration. These compositional alterations appeared to be responsible, at least in part, for the differences in fluidity noted between treated and control plasma membranes. These results therefore demonstrate that dexamethasone administration can modulate the lipid fluidity and lipid composition of rat proximal-small-intestinal brush-border membranes.

Dexamethasone-induced alterations in the glycosphingolipids of rat proximal small-intestinal mucosa

Prior studies have demonstrated that glucocorticoids can influence the structure and function of several different organs, including the small intestine. However, to date, the effects of glucocorticoids on the glycosphingolipids of the rat small intestinal mucosa have not been examined. In the present experiments, male albino rats of the Sherman strain were subcutaneously administered dexamethasone (100 micrograms/100 g body wt. per day) or diluent for 4 days, and the ceramide, acidic and neutral glycosphingolipid compositions of the proximal small intestine of these animals were examined and compared. The results of these studies demonstrate that dexamethasone administration: (1) increased the content and relative percentage of hematoside (GM3) in this tissue; (2) increased the percentage of N-glycoylneuraminic acid of hematoside; (3) decreased the percentage of the long-chain base phytosphingosine of hematoside, glucosyl- and globotriaosylceramide; and (4) did not appear to influence significantly the concentration of the neutral glycosphingolipids or ceramide in this tissue. These data, therefore, indicate that dexamethasone administration induces alterations in the glycosphingolipids, particularly hematoside, of rat small-intestinal mucosa.

Modulation of Na+-H+ exchange by ethinyl estradiol in rat colonic brush-border membrane vesicles

Prior studies by our laboratory have suggested that a relationship may exist between rat colonic brush-border membrane vesicular fluidity and Na+-H+ exchange. To further explore this possible relationship, in the present studies the effects of ethinyl estradiol (17 alpha-ethinyl-1,3,5-estratriene-3,17-beta-diol) administration subcutaneously (5 mg/kg body wt. per day) for 5 days, on rat colonic brush-border membrane fluidity and Na+-H+ exchange were examined. This treatment regimen has previously been shown to decrease the lipid fluidity of rat hepatic and rabbit small intestinal plasma membranes. In agreement with these prior studies, the present results demonstrate that this agent decreases the lipid fluidity of treated-rat colonic brush-border membranes compared to control membranes, as assessed by steady-state fluorescence polarization techniques using three different fluorophores. An increase in the cholesterol content and cholesterol/phospholipid molar ratio of treated-membranes appear to, at least partially, be responsible for the fluidity differences. Furthermore, examination of the kinetic parameters for amiloride-sensitive sodium-stimulated proton efflux in treated and control membrane vesicles, utilizing the pH-sensitive fluorescent dye, Acridine orange, revealed that ethinyl estradiol administration decreased the Vmax for this exchange mechanism, expressed in arbitrary fluorescence units, by approx. 25% but did not influence its Km for sodium. These data, therefore, lend further support to the contention that alterations in fluidity may modulate Na+-H+ exchange in rat colonic brush-border membrane vesicles.

Estrogen-induced alterations of hematoside of rat small intestinal mucosa

Prior studies have suggested that sex hormones could influence the ganglioside and/or neutral glycosphingolipid composition of various organs. To date, the effects of sex hormones on the glycosphingolipid composition of the rat small intestinal mucosa, however, have not been examined. In the present studies, male albino rats of the Sherman strain were subcutaneously administered the synthetic estrogen, ethinylestradiol (5 mg/kg body wt. per day), or diluent for 5 days, and the ganglioside, neutral glycosphingolipid and ceramide composition of the small intestinal mucosa of these animals were analyzed and compared. The results of these experiments demonstrate that estrogen administration: increased the ganglioside concentration of this tissue, including hematoside (Gm3); increased the percentage of the long-chain base phytosphingosine of hematoside; and did not appear to significantly influence the concentration or composition of the neutral glycosphingolipids or ceramide in this tissue. These data, therefore, indicate that estrogen administration induces quantitative and qualitative alterations in the gangliosides but not in the neutral glycosphingolipids or ceramide of rat small intestinal mucosa.

Intraluminal calcium modulates lipid dynamics of rat intestinal brush-border membranes

The present investigations were performed to evaluate whether calcium modulates the physical state and lipid composition of rat enterocyte plasma membranes in vivo. Ca2+ [CaCl2 (50 mM) in NaCl] or NaCl (vehicle control) was administered to rats by intraluminal (gavage) or intraperitoneal routes. Sixty minutes later, brush-border (BBM) and basolateral membranes (BLM) were prepared from the proximal small intestine. By use of the fluorophores, DL-2-(9-anthroyl)-stearic acid (2-AS), DL-12-(9-anthroyl)-stearic acid (12-AS), and 1,6-diphenyl-1,3,5-hexatriene (DPH), steady-state fluorescence polarization studies demonstrated that intraluminal calcium decreased the fluidity of BBM but not BLM compared with their respective vehicle controls. These alterations in fluidity could, at least in part, be attributed to the concomitant increase in sphingomyelin content and the sphingomyelin/lecithin ratio (mol/mol) observed in the BBM prepared from calcium-gavaged rats. To evaluate the mechanism for these lipid alterations, enzyme activities involved in sphingomyelin synthesis and degradation were measured and revealed an increase in sphingomyelin synthase and a decrease in sphingomyelinase in BBM prepared from calcium-gavaged rats. In contrast, intraperitoneal administration of calcium failed to influence membrane fluidity, lipid composition, or these enzymatic activities in either BBM or BLM.

Premalignant alterations in the glycosphingolipid composition of colonic epithelial cells of rats treated with 1,2-dimethylhydrazine

1,2-Dimethylhydrazine is a procarcinogen with selectivity for the colon. In weekly s.c. doses of 20 mg/kg of body weight, this agent produces colonic tumors in virtually 100% of rodents, with a latency period of approximately 6 months. To determine whether alterations in the glycosphingolipid content and composition of rat colonic epithelial cells existed before the development of dimethylhydrazine-induced colon cancer, rats were given s.c. injections of this agent (20 mg/kg body weight per week) or diluent for 5 weeks. Animals were sacrificed at this time period and colonocytes isolated from each group. Glycosphingolipids were then extracted from these cells and analyzed by thin-layer chromatography, high-performance liquid chromatography and gas-liquid chromatography. The results of these studies demonstrate that: (a) the content and relative percentages of globotriaosylceramide is increased, whereas hematoside and globotetraosylceramide are decreased in dimethylhydrazine-treated colonocytes compared to their control counterparts; and (b) differences in the enzymatic activities responsible for the biosynthesis of these glycosphingolipids appear to explain, at least partially, these compositional differences. The present data, therefore, suggest that alterations in certain glycosphingolipids may be an early event in colonic malignant transformation and, furthermore, that these alterations may prove useful in the detection of early colon cancer.

1,2-Dimethylhydrazine-induced alterations in colonic plasma membrane fluidity: restriction to the luminal region

Recently, work in this laboratory has shown that changes in the 'dynamic' component of fluidity, lipid composition and phospholipid methylation activity of distal colonic brush-border membranes could be detected after administration of 1,2-dimethylhydrazine to rats of the Sherman strain for 5-15 weeks, i.e., before the development of colon cancer. The present experiments were therefore conducted to: determine whether similar 'premalignant' biochemical changes could be detected in basolateral membranes of Sherman rats treated with this agent; and clarify the relationship of these membrane changes to the malignant transformation process by examining the effect of 1,2-dimethylhydrazine on these biochemical parameters in colonic antipodal plasma membranes of rats of the Lobund-Wistar strain. This particular strain of rats has previously been shown to be total resistant to the induction of tumors by 1,2-dimethylhydrazine. The results of the present experiments demonstrate that similar biochemical alterations could not be detected in the colonic plasma membranes prepared from either strain of rat treated with 1,2-dimethylhydrazine. These data support the contention that the prior biochemical membrane alterations noted in brush-border membranes of 1,2-dimethylhydrazine-treated animals are, in fact, related to the malignant transformation process and, furthermore, are confined to the luminal surface of distal colonic epithelial cells.

The role of sphingomyelin synthetase and sphingomyelinase in 1,2-dimethylhydrazine-induced lipid alterations of rat colonic plasma membranes

Recently, our laboratory, utilizing the 1,2-dimethylhydrazine model of colonic adenocarcinoma, demonstrated alterations in the 'dynamic component' of fluidity in brush-border membranes prepared from distal colonocytes of rats administered this agent for 5, 10 and 15 weeks, i.e., before the development of colon cancer. Furthermore, changes in the sphingomyelin content and sphingomyelin/phosphatidylcholine molar ratio of these membranes appeared, at least partially, to be responsible for these fluidity alterations. In an attempt to elucidate the mechanism(s) involved in these dimethylhydrazine-induced lipid changes, in the present studies the activities of sphingomyelin synthetase and magnesium-dependent neutral sphingomyelinase, enzymes involved in the synthesis and degradation of this phospholipid, respectively, were examined and compared in distal colonic brush-border membranes prepared from rats after 5, 10 or 15 weeks administration of dimethylhydrazine or diluent. The results of these studies demonstrate that alterations in both these enzymatic activities can be detected after administration of dimethylhydrazine and appear to, at least in part, be responsible for the changes in membrane sphingomyelin composition noted previously. These results as well as a discussion of their possible serve as the basis for the present report.