αand Luteinizing HormoneβMessenger Ribonucleic Acid (RNA) of Male and Female Rats after Castration: Quantitation Using an Optimized RNA Dot Blot Hybridization Assay*

Abstract

In this study we examined the changes in alpha and LH beta mRNAs in anterior pituitaries of male and female rats after castration. mRNA concentrations were measured by an optimized RNA dot blot hybridization assay. Rat alpha and LH beta cDNAs were nick-translated to specific activities of 2-5 X 10(8) cpm/micrograms and were used as hybridization probes. The total RNA per assay, RNA per dot, and saturating amounts of probe were optimized. The intra- and interassay coefficients of variation were 5% and 28%, respectively. Both alpha and LH beta mRNA concentrations increased after castration, but marked differences were observed in the kinetics of responses in male and female rats. In males, alpha and LH beta mRNAs were increased by 24 h postcastration (by 25% and 38%, respectively), and 4- to 5-fold increases over intact controls were evident by 18 days. Alpha mRNA rose rapidly and had doubled by 2 days, whereas LH beta mRNA concentrations showed a similar increase by 6-7 days postcastration. The slower rise in LH beta mRNA was associated with a transient decline in serum and pituitary LH concentrations between 2 and 6 days after castration. In female rats, alpha mRNA increased more slowly. Alpha concentrations had doubled by 10 days, while a similar increase in LH beta mRNA occurred 7 days after castration. Thereafter, both subunit mRNAs continued to rise, and by day 20 alpha mRNA was increased 5-fold and LH beta mRNA 16-fold over values in intact females. Serum and pituitary LH concentrations rose gradually, and both were increased by 7-10 days after castration. The increase in serum and pituitary LH followed a time course similar to that of the progressive rise in LH beta mRNA concentrations. These data show that an increase in steady state LH subunit mRNA concentrations is one of the mechanisms involved in increased gonadotropin biosynthesis and secretion after castration. The kinetics of LH subunit mRNA and LH secretory responses are different in male and female rats and suggest that the concentration of LH beta mRNA may be a limiting factor in LH secretion.

Effects of long-term treatment with resveratrol and subcutaneous and oral estradiol administration on pituitary function in rats

“…Changes in LH mRNA expression result from transcriptional regulation of these separate subunits that have individual sensitivity to E2. In accordance with the literature, castration of female rats resulted in increased levels of both subunit mRNAs (Gharib et al 1986, Papavasiliou et al 1986). We observed the LH subunit mRNA was most strikingly regulated with post-OVX values that were 15-fold higher than in intact animals; -subunit mRNA expression was stimulated to a lesser extent (5-fold).…”

“…In contrast, prolactin levels are suppressed upon OVX and rise after treatment with E2 (Raymond et al 1978). It is furthermore known that, following OVX, LH , LH , GnRH receptor, and estrogen receptors (ERs) are modulated (Gharib et al 1986, Papavasiliou et al 1986, Shupnik 1996. These experiments, however, were conducted under short-term OVX or E2 replacement conditions.…”

Expression and regulation of the pituitary- and placenta-specific human glycoprotein hormone alpha-subunit gene is restricted to the pituitary in transgenic mice.

“…Significant increases in the steady-state levels of alpha-subunit and LH beta-subunit mRNAs are seen in the pituitaries of orchectomized male rats (1,40). To determine whether gonadectomy has a similar effect on the expression of the endogenous mouse and introduced human alpha-subunit genes in transgenic mice, groups of male transgenic and nontransgenic control animals were orchectomized and sacrificed 1 month later to examine the levels of endogenous and transgenic alpha mRNA in their pituitaries.…”

“…TSH production is stimulated by hypothalamic thyrotropin-releasing hormone and suppressed by thyroid hormones. Steroid regulation of LH and FSH has been demonstrated in castrated animals, which have significantly increased levels of these gonadotropins in their pituitaries and sera (1,2,21,33,40). Moreover, these levels can be suppressed by replacement steroid therapy (2,34,39,49).…”

Multimodal control of pituitary gonadotropin biosynthesis. Effects of gonadal steroids, GnRH, cyclicAMP and diacylglycerols

“…We also observed this inhibitory effect of gonadal steroids by in vitro treatment using pituitary cells from castrated rats in primary cultures (Mogenet-Corbani, 1986). The (Nilson et al, 1983 ;Papavasiliou et al, 1986) and in rats (Abbot et al, 1985 ;Gharib et a/., 1986).…”