Effects of thyroxine on oestrogen receptor concentrations in anterior pituitary and hypothalamus of hypothyroid rats

Ceppi, Jorge A.; Ritta, Mónica N.; Calandra, Ricardo S.; Zaninovich, Angel A.

doi:10.1677/joe.0.1190383

Cited by 7 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is precedence for estrogen regulating somatotroph function. Estrogen stimulates GH secretion from the pituitary (36,37), and somatotrophs have been shown to bind [3H]estradiol in females in an ovarian-dependent fashion (38). Furthermore, in the present study OX caused a 4-fold increase in the SP-expressing somatotroph population over the percentage seen in cycling females and in OX estrogen-stimulated rats.…”

Section: Resultssupporting

confidence: 59%

“…But thyroid status may affect pituitary cell types other than thyrotrophs. For instance, thyroid hormone replacement can reverse thyroidectomy-induced decreases in [3HJestradiol binding in the AP (38), and decreases in [3H]estradiol binding in the hypothyroid state occur not only in thyrotrophs but in somatotrophs as well (39). This fact indicates that thyroid hormones may up-regulate estrogen receptors in the somatotroph population, as has been demonstrated also in liver and kidney (40,41).…”

Section: Resultsmentioning

confidence: 72%

See 1 more Smart Citation

Sexually dimorphic distribution of substance P in specific anterior pituitary cell populations.

Brown

Roth

Krause

1991

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Substance P (SP) immunoreactivity is detectable in the rat pituitary by RIA; however, immunollization has been difficult. We used a sensitive immunogold silverenhancement staining technique to cytochemically locate SP in the gland. SP-lmmunoreactive (SP-ir) cells were seen in anterior pituitary (AP), and occasional SP-ir fibers and terminals were seen in both AP and posterior pituitary. Coloalization studies showed the vast majority of SP-ir cells in the male AP to be also immunoreactive for growth hormone (GH). These GH/SP-ir cells represent -23% ofthe somatotroph population in the male. SP-ir cells did not colocalize with lactotrophs, gonadotrophs, or corticotrophs; however, rare thyroidstimulating hormone/SP-ir cells were found in the male AP. Comparisons of pituitaries from males and females revealed that females have 70% fewer SP-Ir cells and that only =%6% of the somatotrophs in the female express SP. This sexual dimorphism is diminished in 6-day ovariectomized rats because this treatment increases the GH/SP-ir cell population 3-fold. This result suggests that the previously reported estrogen-induced decrease in SP gene and peptide expression in the pituitary occurs, at least in part, in a subpopulation of somatotrophs. To test this hypothesis, distribution of SP-ir cells was examined in pituitaries from estrogen-and oil-treated ovariectomized rats. Estrogen reduced the percentage of somatotrophs with SP immunoreactivity by 70% compared with ovariectomized oiltreated controls, indicating that estrogen most likely regulates SP levels in the pituitary by acting on a subpopulation of somatotrophs to suppress SP expression. Estrogen does not appear to alter SP immunoreactiviy that is detected in the additional population of SP cells that colocalize with thyroidstimulating hormone. These SP-expressing thyrotrophs were seen 6-fold more frequently in the female than in the male pituitary, regardless of steroid status. These studies reveal that males have more total SP-ir cells in the AP than do females and that there is a sexually dimorphic pattern of SP distribution in the gland. Males have a higher percentage of SP-ir GH cells, whereas females have more SP-ir thyrotrophs than do males. Identification of independently regulated SP-ir somatotroph and thyrotroph populations provides a basis for investigating the roles of SP in autocrine or paracrine regulation of pituitary hormone secretion.Substance P (SP) immunoreactivity has been detected in the rat anterior pituitary (AP) by RIA (1-4) and by immunohistochemistry in several species (5-12), and SP may act as a local modulator of pituitary function. Northern (RNA) blot and nuclease-protection analyses of RNA isolated from rat APs have revealed the presence of SP-encoding mRNAs in the gland (4, 13, 14), indicating that cells within the AP synthesize SP. Furthermore, SP content in the AP is regulated by gonadal steroids: androgens increase and estrogen decreases pituitary SP levels (2-4), resulting in a sexual dimorphism, such that males have a higher SP co...

show abstract

Section: Resultssupporting

confidence: 59%