Relationship between metabolism of androstenone and skatole in intact male pigs.
The relationship between the metabolism of androsterone and skatole, the major compounds responsible for boar taint, was investigated in F4 Swedish Yorkshire x European Wild Pig intact males. The metabolism of androstenone and skatole were studied in liver microsomes, and the testicular steroid production was measured in testes microsomes. Including androstenone in the assays of skatole metabolism reduced the formation of 6-hydroxyskatole (pro-MII), and three other skatole metabolites (P<.05). The formation of three additional metabolites was not affected. Liver microsomal incubations of androstenone produced two metabolites, I and II. The rate of the formation of metabolite I and the rate of androstenone metabolism were correlated with the rate of skatole metabolism. Liver metabolism of androstenone was not related to levels of androstenone in fat. Testicular synthesis of 16-androstene steroids was correlated with combined synthesis of estrogens and androgens, plasma levels of androstenone, levels of skatole in fat, and skatole metabolism in the liver (P<.05). Plasma levels of estrone sulfate were correlated with levels of skatole in fat and with androstenone levels in fat and plasma and were negatively correlated with synthesis of skatole metabolite F-1 and pro-MII sulfation. These results indicate that the liver metabolism of androstenone and skatole are related. However, it is likely that the relationship between levels of androstenone and skatole in fat is due more to a link between the testicular synthesis of androstenone rather than to the metabolism of androstenone and skatole in the liver. Sex steroids may affect this relationship because of their biosynthesis along with androstenone and possible inhibition of skatole metabolism in the liver. (+info)
Progesterone analogues similarly modulate endometrial matrix metalloproteinase-1 and matrix metalloproteinase-3 and their inhibitor in a model for long-term contraceptive effects.
Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in normal menstruation, while MMP-1 and MMP-3 production by human endometrial stromal cells (HESCs) is repressed in vitro by progesterone. We postulated that the repression by synthetic progestins of MMP production from HESCs may not be fully maintained in the long term, and that this may account for the disturbed uterine bleeding patterns in women using long-acting progestins. In this study, a long-term HESC culture model was established to compare the effects of natural progesterone and a number of synthetic analogues (ORG2058, medroxyprogesterone acetate, norethindrone acetate, levonorgestrel and drospirenone) on the production by these cells of MMP-1 and MMP-3 and TIMP-1. Zymographic and enzyme-linked immunosorbent analysis of culture medium after 2 weeks showed that both natural progesterone and all of the synthetic progestins tested maintained a significant inhibition of MMP-1 and MMP-3 production. Production of mRNA for MMP-1 and MMP-3 was also suppressed by all progestins, while TIMP production was increased. Thus, menstrual bleeding disturbances which occur during the use of synthetic progestins is not likely to result directly from changes in the effect of long-term progestin exposure on MMP-1 or MMP-3 or TIMP-1 production by HESCs. (+info)
Association of cytochrome b5 with 16-androstene steroid synthesis in the testis and accumulation in the fat of male pigs.
The 16-androstene steroids, one of the principal causes of boar taint, are synthesized in the testis by the andien-beta synthase enzyme system. This system has been shown in vitro to involve both cytochrome P450c17 and cytochrome b5. The objective of this work was to investigate the relationship between the levels of cytochrome b5 in the testis, in vitro steroidogenesis, and the accumulation of 16-androstene steroids in the fat of pubertal boars. We found that the in vitro rate of 16-androstene steroidogenesis in testis microsomes was correlated with 16-androstene steroid concentrations in fat (r = .66, P < .01). Western blots were used to determine the amounts of cytochrome b5 and cytochrome P450c17 protein in testis, and two immunoreactive cytochrome b5 proteins of approximately 12 and 16 kDa were found. Levels of cytochrome P450c17 or the high molecular weight cytochrome b5 in testis were not significantly correlated to levels of 16-androstene steroids in fat. However, levels of total cytochrome b5 immunoreactive protein and levels of the low molecular weight immunoreactive cytochrome b5 were correlated to fat 16-androstene steroid concentrations (r = .59, P < .001; r = .72, P = .0001, respectively). Levels of the low molecular weight immunoreactive cytochrome b5 were also correlated to 16-androstene steroid synthesis rates in vitro (r = .62, P < .05). These results indicate that increased levels of a low molecular weight immunoreactive cytochrome b5 protein, and not of cytochrome P450c17, are related to increased testicular 16-androstene steroid production and accumulation in fat. These results support the hypothesis that selection for reduced levels of this low molecular weight immunoreactive cytochrome b5 protein in the testis may result in decreased levels of 16-androstene steroids in fat and reduced boar taint in uncastrated male pigs. (+info)
Use of the steroid derivative RPR 106541 in combination with site-directed mutagenesis for enhanced cytochrome P-450 3A4 structure/function analysis.
RPR 106541 (20R-16alpha,17alpha-[butylidenebis(oxy)]-6al pha, 9alpha-difluoro-11beta-hydroxy-17beta-(methylthio)androst a-4-en-3-one) is an airway-selective steroid developed for the treatment of asthma. Two metabolites produced by human liver microsomes were identified as R- and S-sulfoxide diastereomers based on liquid chromatography/mass spectrometry analysis, proton nuclear magnetic resonance, and cochromatography with standards. Sulfoxide formation was determined to be cytochrome P-450 (CYP) 3A4-dependent by correlation with CYP3A4-marker nifedipine oxidase activity, inhibition by cyclosporin A and troleandomycin, and inhibition of R- (70%) and S- (64%) sulfoxide formation by anti-3A antibody. Expressed CYP2C forms catalyzed RPR 106541 sulfoxidation; however, other phenotyping approaches failed to confirm the involvement of CYP2C forms in these reactions in human liver microsomes. Expressed CYP3A4 catalyzed the formation of the sulfoxide diastereomers in a 1:1 ratio, whereas CYP3A5 displayed stereoselectivity for formation of the S-diastereomer. The high rate of sulfoxidation by CYP3A4 and the blockage of oxidative metabolism at the electronically favored 6beta-position provided advantages for RPR 106541 over other substrates as an active site probe of CYP3A4. Therefore, oxidation of RPR 106541 by various CYP3A4 substrate recognition site (SRS) mutants was assessed. In SRS-4, A305V and F304A showed dramatically reduced rates of R-diastereomer formation (83 and 64% decreases, respectively), but S-diastereomer formation was affected to a lesser extent. A370V (SRS-5) showed decreased formation of the R-sulfoxide (52%) but increased formation of the S-diastereomer. In the SRS-2 region, the most dramatic change in sulfoxide ratios was observed for L210A. In conclusion, the structure of RPR 106541 imposes specific constraints on enzyme binding and activity and thus represents an improved CYP3A4 probe substrate. (+info)
Combined treatment with the 5 alpha-reductase inhibitor PNU 157706 and the antiandrogen flutamide on the Dunning R3327 prostatic carcinoma in rats.
The steroid 5 alpha-reductase enzyme catalyzes the conversion of testosterone to the potent androgen 5 alpha-dihydrotestosterone (DHT). PNU 157706, a novel, potent and selective dual 5 alpha-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. We have studied the efficacy of combined treatment with PNU 157706 and the antiandrogen flutamide in this prostatic tumor in rats. Rats with tumor diameters of about 1 cm were treated orally 6 days a week for 9 weeks with PNU 157706 (10 mg/kg per day) alone or in combination with flutamide (1 and 5 mg/kg per day). Animals were killed 24 h after the last treatment and ventral prostates were removed for testosterone and DHT determination. PNU 157706 reduced the growth of established tumors by 36%; flutamide showed a slight effect at 1 mg/kg per day (24% inhibition), while at the dose of 5 mg/kg per day it reduced tumor growth by 48%. The combination of PNU 157706 with the lower dose of flutamide caused an additive tumor growth inhibition (60%) and the combination with the higher dose of flutamide resulted in a better inhibition of tumor growth (68%) than did either treatment alone. Castration resulted in marked tumor growth inhibition (76%). Ventral prostate weight was more markedly reduced by PNU 157706 treatment than by flutamide; combined treatment was as effective as castration. Prostatic DHT content was markedly reduced by PNU 157706 (93%), whereas prostatic testosterone increased (137%). Concomitant treatment with flutamide partially antagonized the testosterone increase induced by PNU 157706 and did not modify the already considerable suppression of DHT. These data show that the inhibitory effects of PNU 157706 and flutamide on Dunning prostatic tumor growth are additive, thus supporting the rationale of this combination therapy in advanced prostate cancer, in order to achieve adequate androgen blockade with minimal side-effects. (+info)
Social effects and boar taint: significance for production of slaughter boars (Sus scrofa).
A study was conducted to elucidate the effects of social factors on the concentrations of boar taint substances, androstenone and skatole, in boars. The factors included dominance (social rank) and the effects of strongly tainted animals on other members of the group. Four successive replicates of 100 pigs (50 boars + 50 gilts) with an average live weight of 24 kg were randomly allocated to 10 pens of 10. Data for this study were collected during the period of 67 to 114 kg of live weight and included the repetitive recording of agonistic behavior during competitive feeding; blood sampling for determination of plasma androstenone, skatole and testosterone in boars; feces sampling for determination of skatole content; and collection of bulbourethral glands in boars, and uteri plus ovaries in gilts at slaughter, for the assessment of sexual maturity. Results show an influence of social rank on plasma concentrations of androstenone (P = .0001) and testosterone (P = .0001), the weight of the bulbourethral glands (P = .0001), and plasma skatole (P = .02). Pens were classified according to the pig with the highest concentration of androstenone in the pen into high, medium, and low maximum pens. In pens with high maximum concentrations of androstenone, the second-highest androstenone concentration (P = .0001), and the average concentration (P = .0003) in the pen were higher than those in pens with medium or low maximum concentrations of androstenone. Mean aggression level was also higher (P = .02), but pens with high maximum aggression level did not have higher mean androstenone concentration. Rank effect on androstenone was more important than aggression effect. Neither maximum androstenone concentration nor maximum aggression level in a pen was related to the pen mean stage of sexual maturity in either sex. No influences of rank, aggression, or aggression received were found on the feces skatole level, and no pheromonal communicative function was demonstrated for skatole. High androstenone concentrations did not have a suppressive effect on androstenone concentrations in other males of the group; on the contrary, the levels were increased. This may be due to a stimulating effect of androstenone and, possibly, mating activity. Consequently, in the production of boars for slaughter, strongly tainted animals should be avoided or removed and mating activity minimized. This could be facilitated by, for instance, slaughtering before sexual maturity or separate rearing of the sexes. (+info)
Cholesterol movement in Niemann-Pick type C cells and in cells treated with amphiphiles.
Cholesterol accumulates to massive levels in cells from Niemann-Pick type C (NP-C) patients and in cells treated with class 2 amphiphiles that mimic NP-C disease. This behavior has been attributed to the failure of cholesterol released from ingested low density lipoproteins to exit the lysosomes. However, we now show that the rate of movement of cholesterol from lysosomes to plasma membranes in NP-C cells is at least as great as normal, as was also found previously for amphiphile-treated cells. Furthermore, the lysosomes in these cells filled with plasma membrane cholesterol in the absence of lipoproteins. In addition, we showed that the size of the endoplasmic reticulum cholesterol pool and the set point of the homeostatic sensor of cell cholesterol were approximately normal in NP-C cells. The plasma membrane cholesterol pools in both NP-C and amphiphile-treated cells were also normal. Furthermore, the build up of cholesterol in NP-C lysosomes was not a physiological response to cholesterol overload. Rather, it appeared that the accumulation in NP-C lysosomes results from an imbalance in the brisk flow of cholesterol among membrane compartments. In related experiments, we found that NP-C cells did not respond to class 2 amphiphiles (e.g. trifluoperazine, imipramine, and U18666A); these agents may therefore act directly on the NPC1 protein or on its pathway. Finally, we showed that the lysosomal cholesterol pool in NP-C cells was substantially and preferentially reduced by incubating cells with the oxysterols, 25-hydroxycholesterol and 7-ketocholesterol; these findings suggest a new pharmacological approach to the treatment of NP-C disease. (+info)
The tetraspanin CD63/lamp3 cycles between endocytic and secretory compartments in human endothelial cells.
In the present study, we show that in human endothelial cells the tetraspanin CD63/lamp3 distributes predominantly to the internal membranes of multivesicular-multilamellar late endosomes, which contain the unique lipid lysobisphosphatidic acid. Some CD63/lamp3 is also present in Weibel-Palade bodies, the characteristic secretory organelle of these cells. We find that CD63/lamp3 molecules can be transported from late endosomes to Weibel-Palade bodies and thus that CD63/lamp3 cycles between endocytic and biosynthetic compartments; however, movement of CD63/lamp3 is much slower than that of P-selectin, which is known to cycle between plasma membrane and Weibel-Palade bodies. When cells are treated with U18666A, a drug that mimics the Niemann-Pick type C syndrome, both proteins accumulate in late endosomes and fail to reach Weibel-Palade bodies efficiently, suggesting that P-selectin, like CD63/lamp3, cycles via late endosomes. Our data suggest that CD63/lamp3 partitions preferentially within late endosome internal membranes, thus causing its accumulation, and that this mechanism contributes to CD63/lamp3 retention in late endosomes; however, our data also indicate that the protein can eventually escape from these internal membranes and recycle toward Weibel-Palade bodies to be reused. Our observations thus uncover the existence of a selective trafficking route from late endosomes to Weibel-Palade bodies. (+info)