Retraction: Nuclear Morphometric Analysis of Leydig Cells of Male Pubertal Rats Exposed In Utero to Di(n-butyl) Phthalate.

[This retracts the article on p. 439 in vol. 26, PMID: 24526819.].

In Utero Exposure to 3,3',4,4', 5-Pentachlorobiphenyl Dose-Dependently Induces N-butyl-4-(hydroxybutyl) Nitrosamine in Rats With Urinary Bladder Carcinoma.

Polychlorinated biphenyls (PCBs) are fat-soluble environmental pollutants that can accumulate in adipose tissue or be secreted in milk. N-butyl-4-(hydroxy butyl) (BBN), a rat bladder carcinogen, recruits the host metabolism to yield its ultimate carcinogenic form via CYP1s. Since estrogen receptors (ERs) mediate biological responses important for the growth of bladder carcinoma, we investigated PCNA, Cyclin D1, ERs, CYP1s, and AhR expression in BBN rat bladder carcinomas with prenatal PCB exposure. Female SD rats were treated with 7.5 µg, 250 ng, and 2.5 ng of 3,3',4,4',5-pentachlorobiphenyl (PCB126)/kg or vehicle on days 13 to 19 post-pregnancy. Six-week-old male offspring were treated with 0.05% BBN for 10 weeks before being anesthetized and the urinary bladder wall incised to expose the bladder carcinomas. N-butyl-4-(hydroxybutyl) bladder carcinoma incidence increased with prenatal PCB exposure dose-dependently. In bladder carcinoma, PCB126 exposure significantly increased PCNA, D1, ERα, CYPIA1, CYP1B1, and AhR expression dose-dependently, and increased ERα expression was particularly prominent. However, the expression of ERß was low, independent of the volume of PCB126 given, indicating similarity to the Vehicle group. We conclude that prenatal PCB126 exposure in rats can induce PCB126 to dose-dependently metabolize BBN via CYP1A1, and contribute to bladder carcinogenesis with upregulation of ERα expression.

In Utero Exposure to Di( n-butyl)phthalate Induces Morphological and Biochemical Changes in Rats Postpuberty.

Pregnant Sprague-Dawley rats were orally administered di( n-butyl)phthalate (DBP; 100 mg/kg/day) on gestation days (GD) 12 to 21. We investigated the male offspring and probed morphological alterations in Sertoli cells at 7, 9, 14, and 17 weeks of age. Parameters assessed in this study included offspring number, sex ratios, body weights, testis weights, seminiferous tubule (ST) profile numbers and diameters, number of vimentin-labeled Sertoli cells, and both testosterone and follicle-stimulating hormone (FSH) levels. Testicular weight/body weight ratios and the numbers and diameters of ST in maximum transverse testicular sections were statistically similar at weeks 7 and 9; however, at weeks 14 and 17, they were statistically different and displayed higher BrdU-positive Sertoli cells/Sertoli cell ratios in the DBP treatment group. Noteworthily, the serum FSH levels were higher and testicular testosterone levels were lower in the DBP treatment group. To our knowledge, the present study is the first to report that in utero DBP exposure significantly increased Sertoli cell numbers and their cellular proliferation from postpuberty to adulthood, with a significant decrease in testicular testosterone and an increase in FSH.

Three-dimensional reconstruction of deferent ducts papillae in urogenital duct system of the male rat.

BACKGROUND: The rodent ejaculatory ducts penetrate the male accessory sex gland complex and open into the urethra, anatomically similar to humans. Although the deferent ducts papillae in rodents have been described at the distal end of deferent ducts, they are absent in humans, and their detailed morphology has been unclear. METHODS: The detailed anatomical structures of the distal end of the deferent ducts of rats were investigated by the computer assisted three-dimensional reconstruction analysis using serial sections of the male accessory sex gland complexes in rats. RESULTS: The present study revealed that a pair of deferent ducts enters the ventral side of the male accessory sex gland complex, runs caudally parallel to the urethra, and then exits at about midsection of the dorso-lateral lobe of prostate. They are composed of mammilliform papillae, called the deferent duct papillae, which dorso-laterally protrude into the duct lumen from intra-ventral portion of the main duct of ampullary gland. The internal surface of the deferent ducts papillae is composed of ciliated columnar epithelium continuous from the deferent ducts, while their external surface is composed of the columnar secretory epithelium of the ampullary glands. Sphincter muscles were not observed in the deferent ducts papillae, while their lamina propria were occupied by many arterial or venous capillaries. CONCLUSIONS: The deferent ducts of rat terminated at the deferent ducts papillae that located at the main duct of ampullary glands that drained into the urethra. The deferent ducts papillae might be controlled by the expansion/contraction of well-developed papillary mucosal capillary vessels.

Adenocarcinoma of the ampullary glands of the ductus deferens in a Sprague-Dawley rat.

Spontaneously occurring proliferative lesions of the male accessory sex glands are infrequent in various strains of rats. In rodents, the ampullary glands are embedded in the prostate. Although 2 spontaneous cases of atypical hyperplastic lesions at the ampullary gland were previously described in Wistar rats, adenocarcinoma and/or adenoma in this gland have not been reported. This study describes adenocarcinomas in the bilateral ampullary glands in a 52-week-old intact male Sprague-Dawley rat housed as part of a control group in a toxicological experiment. At necropsy, the body weight (644.4 g) and the weight of the prostate with ampullary gland (2.75 g) were similar to others of the same control group, and it had a normal gross appearance. Histopathologically, both ampullary glands revealed microinvasive adenocarcinoma without vascular invasion. The morphological characteristics of the neoplasm varied in different regions of the gland. Other parts of the male accessory sex glands did not show proliferative lesions.

Vascular endothelial growth factor mRNA levels as a biomarker for short-term N-butyl-N-(4-hydroxybutyl) nitrosamine-induced rat bladder carcinogenesis bioassay.

Generically, carcinogenic effects of chemicals in bladder carcinogenesis are judged by induction of papillary or nodular (PN) hyperplasia in rats given N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) for 4 weeks and the test chemical for 22-28 weeks. However, upregulation of vascular endothelial growth factor (VEGF) begins early in rat BBN bladder carcinogenesis. To establish a short-term rat bladder carcinogenic bioassay, we analyzed the correlations between VEGF, VEGF mRNA and bladder lesions inductions at 10 and 26 weeks after BBN treatment. Six-week-old male Wistar (slc) rats were given 0.05% BBN for 4, 10 or 26 weeks. To avoid individual rat bias, the bladders were investigated by partial cystectomy at 10 weeks and total cystectomy at 26 weeks. After induction, PN hyperplasia and carcinoma in rats increased with the length of BBN treatment and immunohistochemical VEGF expression also increased following carcinogenesis, but the immunoreactivity of individual lesions was quite variable. Moreover, induction of PN hyperplasia at 10 weeks' BBN treatment was not significantly correlated with that at 26 weeks' treatment; thus, it was not possible to predict the carcinogenic effect due to the induction of PN hyperplasia at 26 weeks' BBN treatment by that at 10 weeks' treatment. However, VEGF mRNA levels of rat bladders at 10 weeks' BBN treatment revealed a strong significant correlation with the incidence of bladder lesions at 26 weeks' treatment. Here, we suggest that quantitative VEGF mRNA levels are a good biomarker for a short-term BBN-induced bioassay for rat bladder carcinogenesis.

Differences in prostate cancer grade, stage, and location in radical prostatectomy specimens from United States and Japan.

BACKGROUND: To compared prostate cancer at radical prostatectomy between men in the United States (US) and Japan in the modern era. METHODS: Three hundred seventy consecutive totally embedded RP cases (159 US; 211 Japan) from 2010 to 2012 were reviewed. RESULTS: US men were significantly younger (mean age 58.8 years) than Japanese men (mean age 64.6 years; P < 0.00001). Japanese patients presented with higher PSA levels (mean = 10.9 ng/ml) compared to US patients (mean = 5.8 ng/ml, P < 0.00001) and higher clinical stage (P = 0.003). Japanese tumors were: higher grade; larger; more advanced stage; with increased lymphovascular invasion; and more commonly TZ in location (P < 0.00001). In multivariate analysis, independent predictors of high tumor volume were PSA level, clinical stage, TZ location, Gleason grade, and country of origin (Japan). Independent predictors of TZ location were clinical stage, tumor volume, and country of origin (Japan). CONCLUSION: A major factor for larger, higher grade and stage tumors in Japanese patients is the lower prevalence of screening for prostate cancer in Japan. Another contributing factor may be their TZ location, where they are not palpable until advanced and where they are difficult to sample on needle biopsy possibly leading to a delay in diagnosis. The finding of a difference in zonality of prostate cancer between US and Japanese cases is novel and may reflect differences in biology rather than different health care practice between the groups. If this data is confirmed, consideration should be given to TZ sampling as part of routine needle biopsies in Japanese men.

Effects of in utero exposure to di(n-butyl) phthalate for estrogen receptors α, ß, and androgen receptor of Leydig cell on rats.

Estrogens and androgens affect male and female reproductive systems. Recently, we reported that prenatal di(n-butyl) phthalate (DBP) exposure induced atypical Leydig cells (LCs) hyperplasia during adulthood. The present study investigated the expression of estrogen receptor α (ERα), estrogen receptor ß (ERß), and androgen receptor (AR) in LCs of 5-, 7-, 9-, 14-, and 17-week-old Sprague-Dawley (srl) rats whose dams had been administered DBP intragastrically at 100 mg/kg/day or the vehicle (corn oil) from days 12 to 21 postconception. Immunohistochemical, Western blotting, and reverse transcription polymerase chain reaction analyses revealed that the expressions of ERα, ERß, and AR proteins and mRNAs in the DBP group were similar to those of the vehicle group at 5 and 7 weeks, but significantly higher ERα and lower ERß and AR levels were observed in the DBP group at 9 to 17 weeks. The rats prenatally exposed to DBP had seminiferous tubule degeneration and atypical hyperplasia of LCs during adulthood, which was associated with an increase in expression of ERα and a decrease of ERß and AR in the testis.

Male Sprague-Dawley rats exposed to in utero di(n-butyl) phthalate: dose dependent and age-related morphological changes in Leydig cell smooth endoplasmic reticulum.

When 100 mg/kg/day of di(n-butyl) phthalate (DBP) was intragastrically administered to pregnant Sprague-Dawley rats throughout gestation days 12 to 21, the male pups had similar body weights with no apparent physical differences (e.g., litter size, sex ratio) compared to that of the vehicle group. However, prominent age-related morphological alterations in the smooth endoplasmic reticulum (sER) of testicular Leydig cells (LCs) were observed once these animals reached puberty. At weeks 5 to 7, the abundant sER with non-dilated cisternae was distributed in LCs. Subsequently, although the number of LCs significantly increased, the amount of sER was significantly decreased at 9 to 14 weeks of age and had disappeared at 17 weeks. In contrast, the number of LCs and the amount of sER in LCs of the lower dose groups (10, 30, and 50 mg/kg/day) were similar to those of the vehicle group. Further, serum testosterone levels in the 100 mg/kg dose group were significantly lower during 5 to 17 weeks of age. While their luteinizing hormone (LH) level was significantly lower at 5 to 7 weeks of age, it became significantly higher during 9 to 17 weeks. The amount of sER in LCs decreased with age with the increase in LCs proliferation and serum LH levels in rat exposed in utero to DBP in a dose-dependent manner.

Atypical Leydig cell hyperplasia in adult rats with low T and high LH induced by prenatal Di(n-butyl) phthalate exposure.

The present study describes atypical Leydig cell (LC) hyperplasia in 20-week-old Sprague-Dawley rats with low testosterone and high luteinizing hormone levels after prenatal administration of 100 mg/kg/day di(n-butyl) phthalate on days 12 to 21 postconception. Light microscopy revealed LC hyperplasia surrounded by severely degenerated seminiferous tubules. Aggregated LCs had large ovoid nuclei with nucleoli and abundant eosinophilic cytoplasm. Immunohistochemical analysis showed expression of proliferating cell nuclear antigen and vimentin in many hyperplastic LCs. Electron microscopy revealed atypical nuclei, abundant free ribosomes, stripped rough endoplasmic reticulum, intermediate-size filaments, elongated cytoplasmic filopodia, atypical tight junctions, and cilia formations, but smooth endoplasmic reticulum was scarcely observed.

Nuclear Morphometric Analysis of Leydig Cells of Male Pubertal Rats Exposed In Utero to Di(n-butyl) Phthalate.

We recently reported that prenatal rat exposure to di(n-butyl) phthalate (DBP) induced Leydig cell (LC) hyperplasia after nine weeks (wks) of age, yet the number of LCs was similar to that of the vehicle group until seven weeks. Nuclear pleomorphism of hyperplastic LCs is common and is considered to be continuous progressive degeneration. Thus, computer-assisted image cell nuclear analysis of LCs was performed on 5- and 7-wk-old Sprague-Dawley (SD) rats whose dams had been administered DBP (i.g.) at 100 mg/kg/day or vehicle (corn oil) on gestation day 12 to 21. The results of the 5-wk-old DBP group were similar to those of the vehicle group; LC nuclei of the 7-wk-old DBP group showed normal ploidy and similar amounts of DNA. However, the size, elongation and peripheral chromatin aggregation parameters were significantly higher, and the reticular chromatin distribution and isolated chromatin aggregation parameters were significantly lower compared with the vehicle group. The present study quantitatively demonstrated nuclear morphological alterations in rat LCs at 7 wks old (puberty) due to the prenatal DBP administration before apparent LC hyperplasia developed.

Retraction: In utero-exposed di(n-butyl) phthalate induce dose dependent, age-related changes of morphology and testosterone-biosynthesis enzymes/associated proteins of Leydig cell mitochondria in rats.

Editor's AnnouncementIn utero-exposed di(n-butyl) phthalate induce dose dependent, age-related changes of morphology and testosterone-biosynthesis enzymes/associated proteins of Leydig cell mitochondria in ratsMasaya Motohashi, Michael F. Wempe, Tomoko Mutou, Yuya Okayama, Norio Kansaku, Hiroyuki Takahashi, Masahiro Ikegami, Masao Asari, Shin Wakui(The Journal of Toxicological Sciences, 41, 195-206, 2016) I have retracted the above paper as Editor-in-Chief of The Journal of Toxicological Sciences since I have serious concerns about it, primarily due to inappropriate authorship on a non-negligible scale.When it was brought to my attention that there was inappropriate authorship in this paper, I contacted the co-authors to confirm this point. I found out that the majority of them considered their listing as co-authors to be inappropriate. In addition, the majority agreed to the retraction of this paper.These facts raise concerns about the paper. From the standpoint of maintaining the integrity of the research community, I felt that such a paper should be retracted at once.Accordingly, I sent a summary of my concerns about the paper to the corresponding author, Dr. Shin Wakui. I also had an online interview with him to discuss this matter. I told Dr. Wakui that inappropriate authorship on a non-negligible scale is a serious problem that raises concerns about the paper.I prepared a draft of this Editor's Announcement and sent it to Dr. Wakui for review prior to revision and release. Although he did not agree to the retraction, I have decided to take this action from the standpoint of maintaining the integrity of the research community.I coordinated my response to this issue with Dr. Akira Naganuma, Editor-in-Chief of Fundamental Toxicological Sciences, a sister journal of The Journal of Toxicological Sciences. Toshiyuki Kaji, Ph.D.Editor-in-ChiefThe Journal of Toxicological Sciences.

Sertoli cells proliferate in adult rats with prenatal exposure to 3,3',4,4',5-pentachlorobiphenyl.

Sertoli cells play a critical role in spermatogenesis, and in adults, they are terminally differentiated with loss of proliferative activity. This study revealed Sertoli cell proliferation in 17-week-old Sprague-Dawley rats whose dams had been intragastrically administered 250 ng of 3,3',4,4',5-pentachlorobiphenyl/kg on days 13-19 postconception. Immunohistochemical evidence of proliferating cell nuclear antigen (PCNA) expression and electron microscope observation of mitotic figures confirmed the proliferation. Because the serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone concentrations were similar to those of vehicle-treated rats, a direct endocrine cause for the observed effects was unlikely.

Regulation of Prolactin Release at the End Stage of Chicken Embryogenesis.

Difference of onset of increase of PRL content in the anterior pituitary gland and plasma PRL concentration during the late stage of chicken embryogenesis is well known. To investigate the disagreement, changes in PRL content and PRL mRNA levels, and the effects of vasoactive intestinal polypeptides (VIP) on PRL release and PRL mRNA expression were examined using western blot analysis and real-time PCR quantification. Changes in SPRL content were strongly correlated with PRL mRNA levels. The increase in PRL content on day 17 of incubation may be caused by the increase in PRL mRNA levels on day 16 of incubation. Additionally, the effects of VIP on PRL release from the embryonic anterior pituitary gland were not observed until day 18 of embryogenesis. These results suggest that increased levels of PRL mRNA and PRL content in the anterior pituitary gland are closely correlated. However, the increased expression of PRL mRNA observed on day 17 and the initiation of PRL release from the anterior pituitary gland on day 19 were differentially regulated. According to the results of western blot analysis, the proportion of glycosylated PRL (G-PRL) and non-glycosylated PRL (NG-PRL) in the anterior pituitary gland at the end stage of development differed from the proportion of PRL released from the anterior pituitary gland. According to the results of two-dimensional western blot analysis, no isoforms with different isoelectric points were detected in the culture medium on days 19 and 20. These data suggest that the peptide chains of G-PRL and NG-PRL were not modified. In conclusion, the differentiation of PRL-producing cells and the maturation of the hypothalamus and anterior pituitary gland were completed at the end stage of incubation, and that different factors regulated the initiation of PRL mRNA expression before day 18 of incubation.

Prenatal exposure to di(n-butyl) phthalate delays the spermatogenic cycle in rats: Investigation using a BrdU-injection method.

Di(n-butyl) phthalate (DBP) esters are plasticizers that are used to provide transparency and flexibility in household plastic products but can easily leach out to contaminate organisms and the environment. We investigated whether prenatal DBP exposure affects spermatogenesis in rats. Pregnant Sprague-Dawley rats were injected with DBP 10, 50, and 100 mg/kg, or vehicle, administered intragastrically, on gestation days 12-21. At 9 or 17 weeks, 5-bromodeoxyuridine (BrdU) 50 mg/kg was injected intraperitoneally, and one testis was removed 3 h later. The remaining testis was excised 12.95 days + 3 h after the BrdU injection. Immunohistochemical analysis of BrdU was performed with periodic acid-Schiff and hematoxylin counterstaining for a quantitative analysis of the delay in one cycle of spermatogenesis. The DBP 100 mg group showed that the ratio of the appearance of seminiferous tubules in stages VII and VIII were significantly decreased, but those of stages IX and X were significantly increased compared to the Vehicle group. The reference value for the duration of spermatogenesis per cycle was set at 310.8 h. The DBP 100 mg group showed a significant delay in the duration of one cycle of spermatogenesis (16.95 h at puberty and 19.01 h at adulthood) compared with the Vehicle group. This study determined that F1-generation rats with prenatal DBP 100 mg exposure revealed significant accumulation of spermatogenic cells at stages IX to X in the second and third cycles, and the significant delay in the duration of spermatogenesis was more prominent at adulthood than in puberty.

Prediction of clinically insignificant prostate cancer by detection of allelic imbalance at 6q, 8p and 13q.

The criterion tumor volume (TV) for clinically insignificant prostate cancer has been reported, but it differs from study to study: some have reported TV < 200 mm(3); others, < 500 mm(3). The aim of the present study was to distinguish clinically insignificant cancers from significant ones using molecular biological methods. A total of 184 microscopic cancers (MC) defined as limited within a 3 mm circle and 82 main tumor (MT) nodules were selected. Thirteen microsatellite loci at 6q22, 8p23.2-23, 13q14 and 13q33 were evaluated for loss of heterozygosity (LOH). MT were subgrouped as TV > or = 500 mm(3) or < 500 mm(3); TV > or = 200 mm(3) or < 200 mm(3); and TV < 200 mm(3), 200 mm(3) < or = TV < 500 mm(3) or TV > or = 500 mm(3); and frequencies of LOH were compared between these three groups. Frequencies of LOH at 6q16-21, 6q22, 8p23.1, 8p23.2, 13q14 were significantly lower in MC (1.0%, 2.7%, 1.9%, 1.1% and 5.4%) than in MT (30.9%, 40.4%, 12%, 8.7% and 20.6%), but no significant differences in LOH frequency were found within each of the three TV groups, between each cut-off. When insignificant tumor is defined as TV < 200 mm(3) or < 500 mm(3), it should include tumors with malignant potential equivalent to larger tumors. It is suggested that in order to identify insignificant tumor within a strict safety range, TV should be set lower.

Spermatogenesis in aged rats after prenatal 3,3',4,4',5-pentachlorobiphenyl exposure.

We previously reported that prenatal exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB126) had dose-related adverse effects on the spermatogenesis of 7(pubescent)- and 17(adult)-week-old rats, but the effects in middle and old age have been unclear. In this study, the spermatogenesis of male Sprague-Dawley rats whose dams had been injected (i.g.) with 25 pg, 2.5 ng, 250 ng, or 7.5 microg of PCB126/kg or the vehicle on days 13-19 post-conception was investigated at 52 and 90 weeks of age. At 52 weeks, the 7.5 microg group showed a significant decrease of preleptotene spermatocytes in stages VII-VIII seminiferous tubules, round spermatids increased at stages VI-VII and elongated spermatids decreased at stage VIII, while the spermatogenesis of the other PCB-treated groups were similar to that of the vehicle group. At 90 weeks, the 7.5 microg group showed a significant decrease of spermatogenic cells at many stages, and the 250 ng group showed a significant decrease of preleptotene spermatocytes at stages VII-VIII, and round spermatids increased at stages VI-VII, elongated spermatids decreased at stage VIII, and the spermatogenesis of the 2.5 ng and 25 pg groups were similar to those of the vehicle group. The present study showed that prenatal PCB126 exposure had dose-related adverse effects on spermatogenesis in aging rats and may have accelerated spermatogenic senescence. Because the serum testosterone levels of the PCB126 groups and the vehicle group were similar, a direct endocrine cause for the observed effects was unlikely.

Ultrastructural immunohistochemical study of L-type amino acid transporter 1-4F2 heavy chain in tumor microvasculatures of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) induced rat bladder carcinoma.

Angiogenesis is essential for tumor growth, and an enhanced vasculature supplying nutrients and oxygen might reflect malignant potential. L-type amino acid transporter 1 (LAT1/4F2hc) comprises a major nutrient transport system responsible for the Na+-independent transport of large neutral amino acids. Seventy five to seventy eight percent N-butyl-N-(4-hydroxybutyl) nitrosamine-induced rat bladder carcinoma cells showed high LAT1/4F2hc expression. While the intracarcinoma microvasculatures of fenestrated endothelial cells highly expressing LAT1/4F2hc might progressively transport essential amino acids from the microvasculatures to the extracellular matrix, non-fenestrated endothelial cells and pericytes did not. The present study revealed that the tumor angiogenesis is one of target anti-L-type amino acid transporter 1 drug.

Characterization and Expression of Turkey Prolactin Regulatory Element Binding in the Anterior Pituitary Gland and Pancreas During Embryogenesis.

The PRL regulatory element-binding (PREB) protein is a transcription factor that was originally cloned from the rat anterior pituitary gland and characterized as a regulator of the PRL promoter. It is also strongly expressed in several extrapituitary tissues; however, its functional role is not well understood to date. In this study, we aimed to clone and characterize the turkey PREB gene and investigate its mRNA expression in the anterior pituitary gland and pancreas during embryogenesis. Based on the conserved sequence of chicken and mammalian PREB cDNAs, a turkey PREB cDNA fragment was obtained, and after sequencing of the fragment, the 5'-and 3'-ends of mRNA were amplified and determined. To identify the PREB gene structure, polymerase chain reaction (PCR) amplification was performed. The turkey PREB gene consists of 9 exons and 8 introns, and it encodes a 411-amino-acid protein. The expression of PREB mRNA in the anterior pituitary gland was measured during embryogenesis. Levels of PREB mRNA significantly increased at embryonic day 22, with maximum levels being detected on day 25 of ontogeny, which correlated with similar changes in levels of PRL mRNA. The highest level of PREB mRNA was detected on day 19 in the pancreas. However, the highest level of insulin mRNA was detected at embryonic day 25. These results indicate that PREB may be involved in the expression of PRL mRNA in the anterior pituitary gland, whereas insulin mRNA may be expressed independently of the expression of PREB mRNA in the pancreas during embryogenesis.

Effects of Vasoactive Intestinal Polypeptide and Forskolin on mRNA Expression of Prolactin and Prolactin Regulatory Element-Binding Protein in the Anterior Pituitary Gland of Chicken Embryo and Laying Hens.

Vasoactive intestinal peptide (VIP) treatment induced mRNA expression of Prolactin (PRL) in the chicken anterior pituitary gland. VIP responsive element (VRE) of the PRL promoter was identified in the various bird species. However, transcription factor, which binds to VRE, has not yet been identified. Prolactin regulatory element-binding protein (PREB) gene cloned as a candidate transcription factor binds to VRE. Increases of mRNA levels of PRL and PREB during embryogenesis were identified. However, whether VIP affects levels of PRL and PREB mRNA during embryogenesis remains unknown. The effects of VIP and forskolin on mRNA expression of PRL and PREB in the embryonic anterior pituitary gland were assessed. Furthermore, administration of VIP to laying hens was conducted to examine the relationship between VIP and PREB mRNA expression. At day 14 of the embryonic growth stage, VIP treatment did not affect mRNA levels of either PRL or PREB, whereas forskolin treatment induced the increase of these mRNA levels. At day 20, both VIP and forskolin induced an increase of PRL and PREB mRNA levels. The administration of VIP significantly increased mRNA levels of PRL and PREB in the anterior pituitary gland of White Leghorn and Nagoya. These results indicate that the effects of VIP on PRL and PREB mRNA expression levels of VIP receptor may in turn affect PRL and PREB mRNA levels in the chicken anterior pituitary gland.