Sex Difference in Development of Fetal Pituitary-Gonadal Axis

After an exposure of 24 h to synthetic LHRH (100 ng/ml) in vitro, the anterior pituitaries of 4-day-old rats show a notable loss of immunoreactive material in most LH cells in males, but not in females. When radioimmunoassayed without incubation, the pituitary LH content of 4-day-old female rats is 2.8 times higher than that of males of the same age. LHRH treatment stimulates a higher rate of LH discharge in females than in males, but if LH release is expressed as a percentage of the initial pituitary LH content, there is no apparent difference. In both sexes, more than 70% of the initially stored LH is discharged into the medium after 24 h of LHRH stimulation. In males, this discharge produces a pronounced depletion, but in females, the pituitary still contains 78.2% of the initial LH content despite the large amount of hormone released. From these results, it is concluded that in newborn rats the LH synthetic rate in females is higher than that in males. This high synthetic activity, together with the large store of LH, may explain why prolonged LHRH treatment fails to cause LH depletion in females. At 4 days of age LHRH had no stimulatory effect on pituitary synthesis of LH in either sex.

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A correlative radioimmunoassay and immunohistochemical study of LHRH-induced LH depletion in the anterior pituitary of male and female neonatal rats in vitro

Watanabe

Takagi

Kumamoto

1985

Cell Tissue Res.

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Pituitary tumors arising from glycoprotein hormone α-subunit-deficient mice contain transcription factors and receptors present in thyrotropes

et al. 2006

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Glycoprotein-hormone alpha-subunit deficient (alphaSUnull) mice are hypothyroid and hypogonadal due to the absence of functional TSH, LH and FSH, despite normal production of the corresponding beta subunits. Pituitary tumors spontaneously developing in alphaSUnull mice were propagated in hypothyroid mice. The purpose of the current studies was to compare the gene expression profile of these alphaSUnull tumors with previously characterized TtT-97 thyrotropic tumors. A group of animals bearing each tumor type was treated with thyroid hormone (T4) prior to tumor removal. Both tumor types equally expressed TSHbeta mRNA, which significantly decreased when exposed to T4, whereas alpha-subunit mRNA was absent in alphaSUnull tumors. Northern blot analysis was performed using cDNA probes for the following transcription factors: Pit1, GATA2, pLIM, Msx1, Ptx1 and Ptx2. Both tumors were found to contain identical transcripts with similar responses to T4, with the exception of Pit1. In contrast to the signal pattern seen in TtT-97, only two bands were seen in alphaSUnull tumors, which were similar in size to those in alphaTSH cells, a thyrotropic cell line that lacks TSHbeta-subunit expression and Pit1 protein. However, western blot analysis revealed a protein band in the alphaSUnull tumors consistent with Pit1, while this signal was absent in alphaTSH cells. Northern blot analysis was also performed with specific cDNA probes for the following receptors: TRbeta1, TRbeta2, TRalpha1, non-T3 binding alpha2, RXRgamma and Sst5. Similarly-sized transcripts were found in both types of tumor, although the signal for Sst5 was seen in T4-treated alphaSUnull tumors only with a more sensitive RT-PCR analysis. The overall similarity between the two tumor types renders the alphaSUnull tumor as a suitable thyrotropic tumor model.

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VMH lesions and reactivity to electric footshock in the rat: The effect of early testosterone level

Dennis

1976

Physiology & Behavior

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Sex Difference in Development of Fetal Pituitary-Gonadal Axis

Cited by 7 publications

References 9 publications

A correlative radioimmunoassay and immunohistochemical study of LHRH-induced LH depletion in the anterior pituitary of male and female neonatal rats in vitro

A correlative radioimmunoassay and immunohistochemical study of LHRH-induced LH depletion in the anterior pituitary of male and female neonatal rats in vitro

Pituitary tumors arising from glycoprotein hormone α-subunit-deficient mice contain transcription factors and receptors present in thyrotropes

VMH lesions and reactivity to electric footshock in the rat: The effect of early testosterone level

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