Stimulation of Combinatorial Expression of Prolactin and Glycoprotein Hormone α-Subunit Genes by Gonadotropin-Releasing Hormone and Estradiol-17β in Single Rat Pituitary Cells during Aggregate Cell Culture

Abstract

Previously we showed the existence of rat and mouse anterior pituitary cells coexpressing mRNA from two or more hormone genes in which production and/or storage of the corresponding hormones were not detectable. To substantiate a putative function for these cells, we investigated whether these phenotypes were retained during long-term reaggregate cell culture and whether protagonist regulatory factors could expand cell populations expressing particular hormone mRNA combinations. After 4-wk culture and treatments, aggregates were trypsinized and single cells collected by means of a fluo-rescence-activated cell sorter. Hormone mRNAs were detected by single-cell RT-PCR. Combinatorial hormone mRNA expression was retained in culture. Both estradiol (E2) and GnRH (1 nM) markedly augmented the proportion of cells expressing prolactin (PRL) mRNA together with other hormone mRNAs and cells expressing glycoprotein subunit (GSU)-alpha mRNA together with other hormone mRNAs. GnRH strongly increased the proportion of cells containing alphaGSU mRNA alone, but E2 did not. GnRH and (E2) affected the expansion of a population (approximately 20% of all cells) coexpressing PRL and alphaGSU mRNA without betaGSUs. Immunostaining of stored hormone on tissue sections revealed colocalization of PRL and alphaGSU in the E2- but not in the GnRH-treated cells. The present findings suggest that cells coexpressing different pituitary hormone mRNAs form a distinct population that survives without extrapituitary factors. Their occurrence can be markedly modified by regulatory factors. Certain hormone regimens favor unique coexpressions distinctly at mRNA and protein level. These peculiar characteristics support the notion that combinatorial expression of hormone genes in the pituitary serves a biological role.

Estrogen mediated cross talk between the ovary and pituitary somatotrope

“…However, those studies that used concentrations of 10 nM or greater most often reported no effects, or even inhibitory effects of estrogen (Fukata and Martin, 1986;Silverman et al, 1988;Hauspie et al, 2003). Our dose-response results agree that higher concentrations of estrogen are not stimulatory and in fact, may inhibit certain aspects of GH gene product expression (Childs et al, 2004).…”

“…First, there has been controversy about the presence or types of estrogen receptors on somatotropes (Kikuta et al, 1993;Friend et al, 1994;Shupnik, 2002;Stefanneau et al, 1994;Zafer et al, 1995;Chaidarun et al, 1997;Chaidarun et al,m 1998;Gittoes et al, 1999;Shupnik et al1998;Hal and McDonnell, 1999). Second, not all in vitro studies have demonstrated an estrogen-mediated increase in GH synthesis or secretion (Webb et al, 1983;Simard et al, 1985;Lam et al, 1996;Tulipano et al, 2004;Fukuta and Martin, 1986;Silverman et al, 1988;Hauspie et al, 2003.). In some studies, estrogen has had no effects or inhibitory effects on expression of GH (Fukuta and Martin, 1986;Silverman et al, 1988;Hauspie et al, 2003.…”

“…Second, not all in vitro studies have demonstrated an estrogen-mediated increase in GH synthesis or secretion (Webb et al, 1983;Simard et al, 1985;Lam et al, 1996;Tulipano et al, 2004;Fukuta and Martin, 1986;Silverman et al, 1988;Hauspie et al, 2003.). In some studies, estrogen has had no effects or inhibitory effects on expression of GH (Fukuta and Martin, 1986;Silverman et al, 1988;Hauspie et al, 2003. ).…”

Anterior pituitary thyrotropes are multifunctional cells

“…In addition, the existence of a cell pool that costores and cosecretes ACTH and TSH during cold stress has been reported (9). Finally, single-cell RT-PCR has also revealed that ϳ30% of pituitary cells display mRNAs for multiple AP hormones (17,(25)(26)(27)(28) in rats, mice, and monkeys. It is remarkable that most of the cells expressing TSH-␤ mRNA (11%) actually costored it with other AP hormone mRNAs (9%), whereas cells expressing only the TSH-␤ mRNA were much less abundant (2%; see Ref.…”

Retinoic acid and dexamethasone induce differentiation and maturation of somatotroph cells at different stages in vitro

“…Pregnant rats were sacrificed at E13 and the fetal rats obtained under aseptic conditions. The pituitary was separated under a stereomicroscope and a single cell suspension was prepared and cultured as previously reported [7,8]. Briefly, the isolated pituitary was rinsed with DMEM three times and then cut into small pieces and transferred into DMEM with 0.25% trypsin, 100 μg/ mL streptomycin and 100 U/mL penicillin, and cultured at 37˚C with 5% CO 2 for 30 minutes.…”