Molecular cytogenetic analysis of the bladder carcinoma cell line BK-10 by spectral karyotyping.

The bladder cancer cell line BK-10 was established from a grade III-IV transitional cell carcinoma (TCC). BK-10 is near-tetraploid (+/-4n) and consists of two subclones with 20-25 structural aberrations. Here we report the cytogenetic analysis of BK-10 by G-banding, spectral karyotyping (SKY), and FISH. SKY refers to the hybridization of 24 differentially labeled chromosome painting probes and the simultaneous visualization of all human chromosomes using spectral imaging. SKY enabled us to confirm 12 markers in BK-10 previously described by G-banding, redefine 11 aberrations, and detect 4 hidden chromosomal rearrangements, 2 of which had been identified as normal or deleted copies of chromosome 20 and 1 as a normal chromosome 3. Twenty out of 21 translocations identified were unbalanced. FISH analysis of BK-10 using chromosome arm-specific paints, centromere probes, and oncogene/tumor suppressor gene-specific probes revealed a deletion of CDKN2A (p16) in all copies of chromosome 9, a low-level amplification of MYC (five copies), and loss of one copy of TP53; detected the presence of the Y chromosome in a hidden translocation; and detected four copies of ERBB-2. A probe set for BCR and ABL verified breakpoints for all translocations involving chromosomes 9 and 22. A new karyotype presentation, "SKY-gram," is introduced by combining data from G-banding, SKY, and FISH analysis. This study demonstrates the approach of combining molecular cytogenetic techniques to characterize fully the multiple complex chromosomal rearrangements found in the bladder cancer cell line BK-10, and to refine the chromosomal breakpoints for all translocations.

Isolation and characterization of a novel human bladder cancer cell line: BK10.

Molecular studies of bladder carcinomas have aided in determining causative genetic events and the prognosis of cancers endowed with certain abnormalities. In vitro bladder cancer characterization of key cytogenetic alterations is useful for study of molecular changes that may promote oncogenic events. In our laboratory, a novel human bladder cancer cell line, BK10, has been established in vitro and passaged for more than 20 mo. This new bladder cancer cell line (BK10) was derived from bladder tissue containing grade III-IV/IV transitional cell carcinoma. Bladder cancer tissue was obtained at the time of radical cystoprostatectomy extirpation. Cell cultures derived from this surgical sample exhibited an epithelial morphology and expressed epithelial cytokeratins. Immunostains of BK10 were negative for prostate specific antigen (PSA), fibronectin, smooth muscle actin alpha, and desmin. Karyotypic analysis revealed an aneuploid chromosomal content <4n> with many numerical and structural abnormalities previously linked to bladder oncogenesis. Translocations occurred in chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, X and Y. G-banding analysis revealed rearrangements involving chromosomes 9q and 17p, and the location of the ab11 oncogene and the p53 gene, respectively. The availability of this bladder cancer cell line will provide a useful tool for the further study of bladder carcinoma oncogenesis and gene therapy.

Fenretinide: induction of apoptosis and endogenous transforming growth factor beta in PC-3 prostate cancer cells.

N-(4-Hydroxyphenyl)retinamide (4-HPR, Fenretinide) is a retinoid derivative with antineoplastic activity in various tumor types including prostate carcinoma. The mechanism of action of 4-HPR toxicity is unknown. 4-HPR induces apoptosis in leukemia- and lymphoma-derived cells, neuroblastoma, and small cell lung cancers. The present study was designed to investigate: (a) the mechanism of 4-HPR cytotoxicity in prostate cancer cells; and (b) correlate increased expression of transforming growth factor beta 1 (TGF beta 1) with induction of apoptosis. 4-HPR exposure to PC-3 cells in vitro was associated with apoptosis as evidenced by increased incidence of hypodiploid nuclei in propidium iodide fluorescence histograms and DNA fragmentation. An increase in the percentage of nuclei in the G1 phase of the cell cycle preceded induction of apoptosis. TGF beta 1-increased expression was noted in mRNA levels and in secretion of active TGF beta 1 into culture media. TGF beta 1 and TGF-beta receptor type II detected immunohistochemically were increased in 4-HPR-treated PC-3 cells. Furthermore, 4-HPR-induced cytotoxicity in PC-3 cells was abrogated by the addition of anti-TGF beta 1 antibody. In BT-20 cells, a 4-HPR-resistant breast carcinoma cell line, apoptosis was not observed after exposure to 4-HPR nor was TGF beta 1 expression enhanced in stained cells or in conditioned media. It is concluded that 4-HPR induces the expression of TGF beta 1 in association with the induction of apoptosis.

Induction of apoptosis by diethylstilbestrol in hormone-insensitive prostate cancer cells.

BACKGROUND: Diethylstillbestrol (DES) and diethylstilbestrol diphosphate (DESdP) are effective agents for the treatment of advanced prostate cancers. Tumor-inhibiting effects of DES and DESdP are presumed secondary to suppression of androgen production in vivo. Little is known, however, about the direct cellular mechanisms of the tumor inhibition. Estrogens have been reported not only to stimulate growth but also to disrupt microtubule formation in prostate cancer cells. PURPOSE: The study was designed to examine and compare mechanisms of in vitro growth inhibition of DES and DESdP in human androgen-insensitive prostate cancer cells (DU145, 1-LN, and PC-3) and human androgen-sensitive prostate cancer cells (LNCaP) and to examine estrogen receptor modulation of such effects. METHODS: The cytotoxic effects of DES and DESdP were examined in vitro by use of a standard microculture tetrazolium assay to quantitate numbers of viable cells. Immunofluorescence microscopy, DNA fragmentation analysis, and fluorescence flow cytometry were used to investigate microtubules, the induction of apoptosis, and changes in cell cycle distribution. The degree of estrogen receptor positivity of untreated and treated cells was determined by immunohistochemistry and quantitative image analysis. RESULTS: LD50 levels (the dose at which 50% of cells are no longer viable) in the concentration range of 19-25 microM were observed for both DES and DESdP in all cell lines examined. DESdP-induced growth inhibition was found to be dependent on heat-labile phosphatases present in fetal calf serum. DES-induced cytotoxicity was not affected by the presence of 17 beta-estradiol, and it was not dependent on the presence of estrogen receptor. Estrogen receptor-positive cells and estrogen receptor-negative cells were equally responsive to DES. PC-3 cells stained with fluorescent anti-tubulin, phalloidin (actin stain), and 4',6-diamidino-2-phenylindole (DNA stain) showed no inhibition of microtubules or actin filaments but revealed the presence of apoptotic bodies in the nuclei. Fluorescence flow cytometry of nuclear DNA content of propidium iodide-stained nuclei from androgen-insensitive prostate cancer cells treated with 15 or 30 microM DES or DESdP revealed an increase in relative numbers of hypodiploid (apoptotic) nuclei, a depletion of G1- and S-phase cells, and an accumulation of cells in G2/M phase. Conversely, androgen-sensitive cells contained a lower percentage of hypodiploid nuclei but no accumulation of cells in G2/M phase. CONCLUSIONS: Direct cytotoxic effects of DES in prostate cancer cells are estrogen receptor independent and do not involve disruption of microtubule architecture but do involve the promotion of cell cycle arrest and apoptosis. These are the first data confirming direct cytotoxic effects of DES and DESdP in prostate cancer cells via an apoptotic mechanism. IMPLICATIONS. These results suggest that DES and DESdP have potential value as agents against androgen-insensitive prostate neoplasms through induction of an apoptotic cascade.

6-Methylene progesterone is cytotoxic to human cancer cell lines independent of its 5-alpha-reductase activity.

This investigation examined the effects of 6-methylene progesterone (6MP), an irreversible inhibitor of 5-alpha-reductase, on prostatic cancer (PC) cell lines. Dose titration microculture tetrazolium assays were used to evaluate cytotoxicity in cultures treated for 72 hr with 6MP (0-20 micrograms/ml). An androgen-sensitive cell line, LNCaP, was drug-sensitive with a mean 50% lethal dose value (LD50) of 2.632 +/- 0.103. Hormone-resistant PC cell lines 1-LN, DU 145, and PC3 also demonstrated sensitivity with LD50 values between 0.8579-1.110 micrograms/ml with a group average of 1.023 +/- 0.082 micrograms/ml. Increasing dosages of dihydrotestosterone in the growth media did not alter 6MP cytotoxicity in androgen-insensitive prostatic cancer cell lines. No correlation between androgen-responsiveness and 6MP-induced cytotoxicity was observed. In nonprostatic malignancies, 6MP inhibited adenocarcinoma cell lines with a mean group LD50 value of 0.7772 micrograms/ml +/- 0.110. J82, a transitional cell carcinoma cell line of bladder origin, exhibited an average LD50 value of 1.041 +/- 0.260. In an epidermoid cervical cancer cell line, ME180, an LD50 value of 0.5356 micrograms/ml +/- 0.010 was noted. In a melanoma cell line, Du Mel 6, a mean LD50 of 0.7428 +/- 0.023 micrograms/ml was achieved with 6MP. We conclude that 6MP, a novel 5-alpha-reductase inhibitor, has potential as a cytotoxic agent in prostatic carcinoma and additional human malignancies. Further study is justified.

1-dehydro-melengestrol acetate inhibits the growth and protein kinase C activity of androgen-independent Dunning rat prostatic tumors.

Androgen-independent Dunning R3327-AT3 rat prostate tumors are considered an appropriate model of advanced prostate cancer in humans. We recently reported that the progestational steroid melengestrol acetate (MGA) inhibited growth of these tumors on oral administration but also induced a marked involution of adrenals and androgen target organs (prostate, seminal vesicles, and testes). We report herein that the 1-dehydro derivative of melengestrol acetate (dMGA) fed to rats for 21 days also inhibited the growth of Dunning AT3 tumors by approximately 55% without causing a significant regression of adrenals or androgen-dependent tissues. Thus, tumor-growth inhibition was induced by dMGA in the absence of glucocorticoid activity. Cytosolic AT3 tumor fractions obtained by diethylaminoethyl (DEAE)-Sephacel batch chromatography were assayed for lipid- and Ca(2+)-dependent (PKC) and -independent protein kinase activities. Prostatic cytosols had equivalent activity levels of both types of kinases (approximately 2 nmol gamma-[32P]-adenosine 5'-triphosphate (ATP) incorporated mg protein-1 min-1. The PKC activity recovered from the cytosol of untreated AT3 tumors was approximately 4 times higher. Oral administration of dMGA reduced this activity by > 95%. The relationship between protein-kinase activity levels and dMGA-induced growth inhibition of androgen-independent tumors in this animal model is discussed.

Melengestrol acetate and megestrol acetate are prostatic tumor inhibiting agents.

We had previously reported that 6-methylene progesterone, an inhibitor of 5 alpha-reductase, the enzyme which converts testosterone to dihydrotestosterone, markedly inhibited growth of the androgen-dependent Dunning R3327-H rat prostatic tumors. We now find that the progesterone derivatives melengestrol acetate (MGA) and megestrol acetate (MA) inhibit both the androgen-dependent (Dunning R3327-H) and the androgen-independent (Dunning R3327-AT3) prostatic tumors. Growth of the AT3 tumors was suppressed by approximately 53% after 9 days of daily s.c. injections with MGA at 10 mg/kg body weight. MGA also caused a 54% weight reduction of the ventral prostate and a 53% reduction of the seminal vesicles. Adrenal weights were reduced by 42%. A 24-day oral treatment with MGA (at approximately 15-17 mg/(kg.day)) inhibited AT3 tumor growth by 59% and caused a weight reduction in the following tissues: prostate (46%), seminal vesicles (19%), testes (12%), and adrenals (52%). Under the same protocol, MA inhibited AT3 tumor growth by 32% and reduced the weight of the ventral prostate by 49% and the weight of the adrenals by 18%, but had no effect on the seminal vesicles and testes. The extent of the MGA-induced prostatic regression was accompanied by cytological changes similar to those effected by 6-methylene progesterone, i.e., shrinking of the acinar epithelium. The AT3 tumors in MGA-treated rats displayed a limited degree of apoptosis. Atrophy of the adrenal cortex and lowered plasma levels of corticosterone and dihydroepiandrosterone were also observed. A therapeutic role for MGA and MA against androgen-independent prostatic neoplasms in man is forecast by these observations.

Quantitative contribution of factors regulating rat colonic crypt epithelium: role of parenteral and enteral feeding, caloric intake, dietary cellulose level and the colon carcinogen DMH.

To elucidate the role and quantitative contribution of several exogenous factors which may regulate colon crypt mitotic activity, proliferative zone height (PZH) and crypt height, groups of rats were subjected to various feeding regimens both with and without treatment with the colon carcinogen, 1,2-dimethylhydrazine (DMH). The rats were divided into two major groups and one group was given eight weekly injections of DMH base at 9.5 mg kg-1 body weight. Throughout this period and for two additional weeks the rats were isocalorically fed either a defined nutritionally complete diet with different levels of dietary cellulose or they were parenterally (i.v.) fed a nutritionally complete liquid formula with different caloric levels. The rats were then injected with colchicine 3 h prior to sacrifice to arrest and to collect dividing cells at metaphase. The results of multiple regression analysis of all data were interpreted to indicate that parenteral feeding caused dramatic suppression of the colon crypt height (CH) and of the number of metaphase figures per crypt (MC). Increased cellulose intake stimulated CH but suppressed MC. The CH was also stimulated by DMH. CH was positively correlated to PZH and MC. The MC was suppressed by cellulose intake and negatively correlated to PZH but was positively correlated to CH. The PZH was positively correlated to CH. These findings were related to the role of luminal food, functional workload, kcal intake and treatment with DMH on the measured colon crypt parameters. A quantitative assessment of factors that regulate the measured colonic crypt parameters was accomplished.

Prostate. III--A structural feature characteristic of the rat prostate 5 alpha-reductase active site.

To aid in the design of new inhibitors of steroidal 5 alpha-reductase for treatment of prostate cancer, we have studied the topography of the 5 alpha-reductase active site (5 alpha-R) and of the related androgen (RA) and progesterone (RP) receptors in the region complementary to C.6 of progesterone. To this end we have determined the total structures of 17 alpha-acetoxy-6-methylene-4-pregnene-3,20-dione (VII; R = H) and of 17 beta-hydroxy-6,6-ethylene-4-androsten-3-one (VIa) by X-ray crystal structure analysis and, using these data, have developed Newman projections of the 6 alpha-Me, 6 beta-Me, 6-methylene and 6,6-ethylene derivatives of progesterone. From them we have developed a Newman projection of a composite model formed from steroids (V), (VI), (VIIIa) and (VIIIb). This is shown in Fig. 4 and illustrates the relative conformations of these substituents around C.6. From there we proceeded to receptor-binding studies. Our results led to the conclusion that androgen receptor, (RA), takes up preferred but different conformations when bound to testosterone (T) and to 17 beta-hydroxy-5 alpha-androstan-3-one (5 alpha-dihydrotestosterone, DHT), respectively, and that the resulting steroid-receptor complexes bind preferentially to different chromatin acceptor sites. We have therefore used the convention RT and RDHT in place of RA as appropriate. Working on the assumption that binding affinities reflect spatial contours, we have developed comparative silhouettes for the 5 alpha-R, RP and RDHT protein binding sites complementary to C.6 of the steroidal ligand. These data show that the 5 alpha-reductase active site is characterized by a hydrophobic pocket which specifically accommodates a 6-methylenic moiety and partially accommodates a 6 beta-methyl group. RDHT, in contrast, shows much less specificity and largely accommodates all the above substituents. Progesterone receptor differs in failing to accommodate 6,6-ethylene and 6 beta-methyl, with minimal accommodation of 6-methylene. It possesses a hydrophobic pocket skewed towards the alpha-face of the steroid, thereby allowing optimal binding of the 6 alpha-methyl substituent to the receptor. 6-Methylene-4-pregnene-3,20-dione (V) fails to bind significantly to androgen and progesterone receptors thereby supporting the postulate that its antiprostatic activity stems primarily from 5 alpha-reductase inhibition.

Suppression of a a carcinogen (1,2-dimethylhydrazine dihydrochloride)-induced increase in mitotic activity in the colonic crypts of rats by addition of dietary cellulose.

Serial injections of the colon carcinogen, 1,2-dimethylhydrazine (DMH), have been reported to increase the proliferative activity in the colonic crypts preceding development of tumors. Can addition of purified cellulose to a fiber-free AIN-76 rat diet be used to suppress this increase in proliferative activity? To answer this question rats were divided into two groups, and one group was given eight weekly injections of the DMH base at 9.5 mg/kg of body weight. Throughout this period and for 2 additional wk the rats were isocalorically fed a defined nutritionally complete diet both with and without different dietary levels of cellulose (0, 5, and 15%). The rats were given injections of colchicine 3 h prior to sacrifice to arrest and to collect dividing cells at metaphase. Analysis of variance was performed on various morphometric parameters obtained from histological sections of midaxial crypts from the descending colon. Our results confirm that DMH induced a significant increase in the mitotic activity as measured by the number of metaphase figures per crypt. The presence of dietary cellulose did cause a significant suppression of the DMH-induced increase in the crypt mitotic activity.

A comparison of the effects of castration and 6-methylene progesterone, a 5 alpha-reductase inhibitor, on the rat ventral prostate.

6-Methylene progesterone (6MP) is an irreversible in vitro kcat inhibitor of rat prostate 5 alpha-reductase, the enzyme which converts testosterone (T) to dihydrotestosterone (DHT). Treatment of adult rats with 6MP or diethylstilbestrol (DES) decreased the weight of the ventral prostate (VP) by 45%, while castration reduced it by 86%. Histologically, the 6MP-treated VP were indistinguishable from those of controls, while the VP from DES-treated rats showed fibrous stromal hypertrophy as in castrated rats. The prostatic hydroxyproline content, an index of collagen levels, was enhanced by castration or DES, but was not significantly increased by 6MP. Within 2 days of 6MP treatment, the 5 alpha-reductase activity was reduced by 46% and ornithine decarboxylase (ODC) activity was lowered by 27%. During this time the prostatic acid phosphatase activity increased 42% and remained elevated with continued exposure to 6MP up to 13 days. The castration-induced involution of the VP was accompanied by a reduction in serum T and an increase in serum luteinizing hormone (LH). 6MP had no effect on T and LH serum levels but reduced the DHT content within the VP by 64%. Our results indicate that the structure and secretory acid phosphatase activity of the VP are less sensitive to changes in the ratio of T:DHT than is cell proliferation. Thus, the relative amounts of DHT and T within the VP may prove to be more significant than the absolute amount of either androgen in controlling prostate growth or its attendant neoplasms.

Aromatase activity in microsomes from rat ventral prostate and Dunning R3327H rat prostatic adenocarcinoma.

We have measured aromatase activity in microsomes obtained from rat ventral prostate, using the 3H2O release method as described by Weisz. Production of 3H2O from 1 beta-[3H]androstenedione correlated with estrogen production measured by RIA and by TLC. The assay was optimized for incubation time and protein concentration, and used to determine the aromatase activity of ventral prostate microsomes from rats of varying age. Aromatase activity per mg microsomal protein increased from an average of 4 pmol/mg protein X h in 3-month old rats to 68 pmol/mg protein X h in 8-month old rats. Aromatase activity was also measured in microsomes from the Dunning R3327H rat prostatic adenocarcinoma, and was increased in tumors removed 225 days after implantation compared to tumors removed 141 days after implantation. Tumors removed 225 days after implantation from rats which had been treated with DES for 14 days displayed increased aromatase activity compared to untreated tumors. The presence of aromatase activity in the rat ventral prostate and rat prostatic adenocarcinoma would allow regulation of estrogen levels independent of circulating estrogen. Thus, in situ changes in estrogen production with age may contribute to the development of prostatic disease.

Elemental concentration gradients between subcellular compartments.

To gain information on the mechanisms involved in the establishment and maintenance of subcellular gradients of Na, K, Cl and other elements in the flagellate, Euglena gracilis, we turned to the technique of ultracentrifugal stratification of its intracellular contents, which is achieved without loss of viability or cell rupture. Stratified and non-stratified Euglena were cryofixed for energy-dispersive X-ray microanalysis of Na, K, Cl and other elements in thin freeze-dried cryosections. A number of significant elemental concentration differences (expressed as mmol kg-1 dry weight) were found between chloroplast, nucleus, paramylon granules and open cytoplasm (which contained ribosomes, membranes and macromolecules associated with the cytomatrix) in the non-stratified cells. Stratification caused several ions to be redistributed. For example, we observed a significant increase in K and Cl in the nucleus, which was correlated with the condensation of chromatin. Also Cl, but not Na, decreased significantly in the region of cytoplasm that was cleared of observable ribosomes, membranes and macromolecules associated with the cytomatrix, as well as of observable cytochemical enzyme activity. We conclude from the data that more than half of the Cl in open cytoplasm was adsorbed to or entrapped in material that was removed by ultracentrifugation. Thus, it appears that a close association of at least one ion, Cl, with ultracentrifugable material is involved in maintenance of the measured Cl concentration in the open cytoplasm of the non-stratified cell.

Design of cytotoxic steroids for prostate cancer.

Our object was to determine if the aromatic nucleus of estramustine (I) is optimal for binding affinity to prostate cytosolic proteins, and if C3 is the preferred position for the N-mustard carbamate moiety. To this end we have submitted 34 steroids for in vitro assay of binding affinity to total prostate cytosolic proteins. Our structures included aromatic and hydroaromatic steroids containing N-mustard carbamate and other substituents at C3, C6, C11, C16, C17, C20, and C21. Our results show that binding affinity to prostate proteins is optimally present in C3-nitrogen mustard carbamates attached directly to a totally planar aromatic ring as in (IV). Partial deviation from total planarity as in enol-carbamates (V) leads to some loss of binding affinity, which largely disappears in hydroaromatic structures (VI). Thus, our data lead to the Ring A aromatic structure (X) as a basis for the design of steroidal N-mustard carbamates with prostate selectivity. Preliminary in vivo studies using the Dunning R3327AT prostatic adenocarcinoma implanted in the Copenhagen rat generally support our in vitro data.

Approaches to prostatic cancer chemotherapy using the Dunning R3327H prostatic adenocarcinoma.

Androgen-responsive cells: To determine if testosterone or dihydrotestosterone is the main trophic hormone of prostatic adenocarcinoma, we have treated Dunning R3327H prostatic adenocarcinoma-bearing rats with 6-methylene progesterone, which blocks conversion of testosterone to dihydrotestosterone. Copenhagen-Fisher rats were treated with steroid (20 mg/Kg daily) immediately following implantation of tumor and thereafter for 117 days. There was a 92% inhibition of growth of tumors and a lesser effect upon prostate and seminal vesicles. Tumor-free body weights remained unchanged. Both treated and untreated tumors had equivalent DNA content on a per weight basis. This result supports the thesis that prostatic adenocarcinoma requires dihydrotestosterone for growth. Androgen-insensitive cells: Advanced prostate cancer does not respond to endocrine therapy but is temporarily controlled by the cytotoxic steroid estramustine. The latter shows significant selective binding to prostatic protein. To develop chemotherapeutic agents that will control androgen-insensitive cells and possess improved selectivity for prostatic protein, we have studied a number of steroids for their ability to displace 3H-labeled estramustine from prostatic cytosolic proteins. Surprisingly, a carbamido substituent at the C17 position was found to confer significant binding affinity for prostatic estramustine-binding protein. Extension of this structural characteristic to the estramustine type of molecule is being studied.

Endocrine dependence of prostatic cancer upon dihydrotestosterone and not upon testosterone.

Growth of the Dunning R3327-H prostatic adenocarcinoma, implanted in the rat, is inhibited by 6-methylene progesterone. This compound is a potent inhibitor of rat prostatic 5-alpha-reductase and in-vivo produced marked involution of the prostate. Thus the tumor requires dihydrotestosterone and not testosterone for growth.

Proliferative response and renewal of hepatic function following cocaine administration in mice.

Experiments were undertaken to investigate the hepatic, temporal and spatial sequence of events following a single injection of cocaine, a known hepatotoxin. Centrilobular necrosis was induced in male mice (DBA/2Ha) 24 hr post-injection (PI). The time course of hepatic damage was monitored by assaying microsomal cytochrome P450 content, the activity of microsomal FAD-containing monooxygenase (FAD-M) and by determining the levels of serum glutamic pyruvic transaminase (SGPT). Kinetics of the onset of DNA synthesis were determined by autoradiography of thin liver sections and the incorporation of 3H-methyl thymidine into perchloric-acid-precipitable material. There was no increase in the labelling index (LI) and thymidine (TdR) incorporation in the first 24 hr PI. The LI rose to 14.6% and TdR incorporation showed a 5-fold increase over control values 48 hr PI. Both indices declined slightly at 72 hr PI and returned to control values by 96 hr PI. In contrast, the cytochrome P450 content declined by 69%, the FAD-M activity dropped by 40% and the SGPT levels showed an 18-fold increase at 24 hr PI, coincident with cytological signs of necrosis. Although the patterns of recovery differed between these selected enzymes, normal values were attained by 96 hr PI. These results demonstrate that cell damage and hepatic dysfunction precede the onset of DNA synthesis and subsequent proliferation.

Androgenic suppression of mouse hepatic FAD-containing monooxygenase activity.

Sex-related differences in the activity of hepatic FAD-containing monooxygenase (FAD-M) were found in C3H/St mice. Adult female mice had enzyme activities nearly two-fold greater than male mice and these differences, which were absent in sexually immature mice, became apparent at the onset of puberty. The sex differences in hepatic FAD-M appeared to be mediated through the suppressive effect of testosterone; castration of male mice enhanced enzyme activity, while androgenic replacement returned activities to control levels. Testosterone's suppressive effect was found to be relatively specific for hepatic FAD-M. Treatment of castrated male mice with both the anti-androgen flutamide and testosterone returned enzyme activity to control levels, suggesting that testosterone's regulation of hepatic microsomal FAD-M is receptor-mediated. Female gonadectomy had no effect on this enzyme's activity.