Changes in the expression of TGFbeta-isoforms in the anterior pituitary during withdrawal and resumption of feeding in hens.

Our goal was to determine whether TGFbeta-isoforms were involved in the remodeling of the pituitary cell population which occurred by regulation of feeding. The current study examined whether TGFbeta-isoforms were produced in the anterior pituitary, and the mRNA expression of TGFbeta-isoforms changed during withdrawal and resumption of feeding. White Leghorn laying hens were subjected to feed withdrawal for 4 days with a resumption of feeding thereafter. The anterior pituitary tissues were collected from hens of pretreatment (PT), 3 days after feed withdrawal (3DFW), 1 and 5 days after the resumption of feeding (1DRF and 5DRF, respectively), and on the day of resumption of egg-laying (RL). They were processed for semi-quantification of TGFbeta2, beta3, and beta4 mRNA expressions by reverse transcription-polymerase chain reaction (RT-PCR) and for immunocytochemistry for TGFbeta3. TGFbeta2, TGFbeta3, and TGFbeta4 mRNA expression with a product size of 269, 236, and 163bp, respectively, was observed in the anterior pituitaries in all groups of hens. Although the expression of TGFbeta2 and TGFbeta4 mRNA did not show any significant change, that of TGFbeta3 mRNA significantly declined in the 1DRF hens and recovered by the resumption of laying. Immunostaining revealed that TGFbeta3 was located in the cytoplasm of glandular cells with granule forms in all groups of hens. The ovarian and oviductal weights sharply declined in the 3DFW and 1DRF groups, followed by a full recovery in the RL hens. These results indicate that TGFbeta2, beta3, and beta4 were expressed in the chicken anterior pituitary, and TGFbeta3 mRNA expression was changed in correlation with the regulation of feeding, suggesting that this isoform may play a significant role in the regulation of the glandular cell population and/or differentiation.