Requirement of thyrotropin-releasing hormone for the postnatal functions of pituitary thyrotrophs: ontogeny study of congenital @entity1375 in XXXX .

@entity19 @entity1375 @entity1218 @entity6145
We recently reported that @entity1218 -deficient @entity19 showed characteristic @entity1375 . In the present study, we investigated how this @entity1375 occurred particularly in pre- and postnatal stages. Immunohistochemical analysis revealed a number of TSH-immunopositive cells in the @entity1218 -/- pituitary on embryonic day 17.5 and at birth. The mutant pituitary at birth in pups born from @entity1218 -deficient dams also showed no apparent morphological changes, indicating no requirement of either maternal or embryonic @entity1218 for the development of pituitary thyrotrophs. In contrast, apparent decreases in number and level of staining of TSH-immunopositive cells were observed after postnatal day 10 in mutant pituitary. Similar decreases were observed in the 8-week-old mutant pituitary, while no apparent changes were observed in other pituitary hormone-producing cells, and prolonged @entity1218 administration completely reversed this effect. Consistent with these morphological results, @entity1218 -/- @entity19 showed normal @entity6145 levels at birth, but the subsequent postnatal increase was depressed, resulting in @entity1375 . As expected, TSH content in the @entity1218 -/- pituitary showed a marked reduction to only 40% of that in the wild type. Despite @entity1375 in the mutant @entity19 , both the pituitary TSHbeta and alpha mRNA levels were lower than those of the wild-type pituitary. These phenotypic changes were specific to the pituitary thyrotrophs. These findings indicated that 1) @entity1218 is essential only for the postnatal maintenance of the normal function of pituitary thyrotrophs, including the normal feedback regulation of the TSH gene by thyroid hormone; 2) neither maternal nor embryonic @entity1218 is required for normal development of the fetal pituitary thyrotroph; and 3) @entity1218 -deficient @entity19 do not exhibit @entity1375 at birth. Moreover, reflecting its name, @entity1218 has more critical effects on the pituitary thyrotrophs than on other pituitary hormone-producing cells.
