The concentrations of unconjugated oestradiol-17β and oestrone have been measured by radioimmunoassay in the plasma of fetal, newborn and immature guinea-pigs. In fetal plasma, the values of oestradiol ranged from 15 to 50 pg/ml with no significant variations with gestational age except for an abrupt increase at the very end of gestation (148 pg/ml). Low concentrations of oestradiol were also found postnatally (from not detectable to 31 pg/ml) as well as in maternal plasma (22 pg/ml). The values of oestrone were consistently higher in all plasma regardless of age (43–164 pg/ml).

Oestrogen concentrations were also determined in the fetal uterus, lung, kidney and brain and were found to be as much as 60 times higher (per g tissue) than in plasma, especially in the fetal uterus which contained four to five times more than the other tissues. These data correlated well with a 20–90 times greater uptake of [³H]oestradiol by the fetal uterus compared with the other tissues after in-vivo administration of [³H]oestradiol to the fetuses. The selective retention of oestradiol was probably due to the presence of specific oestradiol binding in these fetal tissues, particularly in the uterus whose binding was 60–120 times higher than in the other fetal tissues. Thus, the levels of oestrogen in the circulation of fetal guinea-pigs are low, but the fetal uterus is capable of maintaining a higher concentration which may be important physiologically since oestradiol has been shown to evoke a biological response in the fetal guinea-pig uterus.

Abstract

Cellular receptors for sex steroids (SSRs) were studied in an unselected series of 55 human pituitary tumors. Cytosolic receptors for estrogen (ERcs) and progesterone (PgRcs) were determined in all cases and cytosolic androgen receptors (ARcs) in 47 cases. Nuclear receptors (ERns, PgRns, ARns) were also studied in 33 cases. ERs and PgRs were determined by an ELISA and ARs by [³H]methyltrienolone binding. Where both cytosolic and nuclear receptors were studied (n=33), ERs, PgRs and ARs were found in at least one subcellular fraction in 66·7, 60·6 and 81·8% of cases respectively, ERs and ARs being mainly recovered from the cytosol and PgRs from the nucleus. No linear correlation was found between preoperative plasma steroid hormones and their specific cellular receptors. Nonetheless, the differential expression of SSRs according to sex and gonadal status at the time of surgery strongly supports their regulation by the steroid environment in vivo: PgRcs were more frequent in tumors found in women (41·4 vs 15·4%, P<0·05), whereas a high expression of ERcs and ARcs (>15 fmol/mg protein) was more common in tumors found in men (34·5 vs 10·3%, P<0·05 and 54·5 vs 24·0% respectively). PgRs were positively correlated with ERns, indicating the possibility of estrogen priming of their expression, and negatively correlated with ARs in nuclear fractions. SSRs appeared to be widely distributed among pituitary tumors, although, compared with other hormone-secreting groups, prolactinomas displayed a higher ERc expression (34·8 ± 11·3 vs 4·8 ± 5·1 fmol/mg protein, P=0·007) and gonadotroph cell adenomas lower ARc values (1·3 ± 0·8 vs 38·2 ± 10·6 fmol/mg protein, P=0·048). Microadenomas were characterized by a higher PgR expression than macroadenomas, whereas hemorrhagic (macro)adenomas were characterized by a high ER expression (>90%). The present results indicate that most pituitary tumors are targets for sex steroids, SSR expression being partially triggered by the steroid environment itself. Possible physiopathological and therapeutic implications of these findings are discussed.

Journal of Endocrinology (1996) 151, 175–184

The number of epidermal growth factor (EGF) binding sites was determined by competitive binding assays in a series of 46 pituitary macroadenomas. A single concentration of 125I-EGF (1 nM) was used for all experiments. In four cases, a displacement curve was obtained by adding increasing concentrations of cold EGF, and Scatchard analysis showed the presence of two classes of EGF binding sites, with Kd1 = 0.62 +/- 0.23 nM and Kd2 = 53.8 +/- 8.2 nM for the high- and low-affinity binding sites respectively. The distribution of EGF binding sites was studied in 42 cases by a single-point assay, in the presence and in the absence of a 100-fold cold EGF excess. A non-parametric distribution of EGF binding sites was observed (median 10.2 fmol/mg membrane protein, range 0.0-332.0). EGF-receptor positivity, defined as EGF binding > or = 10.0 fmol/mg protein, was observed in 23 samples (54.8%), especially in prolactinomas (76.5%, P < 0.05 vs other tumors taken together) and in gonadotrope adenomas (62.5%). EGF binding was higher in invasive than in non-invasive adenomas (median: 12.8 vs 0.0 fmol/mg membrane protein, P = 0.047), and especially in adenomas invading the sphenoid sinus (median 26.7 fmol/mg membrane protein, P = 0.008 vs other adenomas). EGF binding also tended to increase with the grade of supra/extrasellar extension according to Wilson (P = 0.15). Sex steroid receptors (SSRs) were simultaneously determined in both cytosolic and nuclear fractions of 31 pituitary adenomas. Estrogen and progesterone receptors were determined by an enzyme-linked immunoassay and androgen receptors by a competitive binding assay with [3H]methyltrienolone. No correlation could be found between EGF binding and either the gender and gonadal status of the patients, or the expression of SSRs by the adenomas. We conclude that the EGF family of growth factors may play a role in the evolution of a significant subset of human pituitary adenomas, especially in their invasiveness, and that a high EGF binding capacity may represent an additional marker of aggressiveness for these tumors. Sex steroids do not appear to have a significant role in the regulation of EGF binding in vivo in these tumors.

Basic helix-loop-helix (bHLH) transcription factors are involved in neuroendocrine cell growth and differentiation. Though NeuroD1 is viewed as corticotroph specific, its overexpression in non-corticotroph pituitary adenomas (PAs) may reflect the activation of molecular pathways involving other bHLH factors, like neurogenins. To search for neurogenin–NeuroD1 molecular pathways in the human normal and tumoural pituitary. Fifty-one PAs – 22 clinically non-secreting (CNS) and 29 secreting respectively – and normal human pituitaries (NP) were studied for NeuroD1 and neurogenins (Ngn1, Ngn2 and Ngn3) gene expression by RT-PCR and quantitative real-time RT-PCR (qRT-PCR). Immunohisto-chemistry for Ngn2/3 was performed in some cases. NeuroD1, Ngn2, Ngn3 and Ngn1 were observed in up to 84.3, 76.5, 30.4 and 9.1% of PA respectively, only NeuroD1 and Ngn2 being frequently overexpressed when compared with NP. Whereas NeuroD1 expression was higher in corticotroph and CNS adenomas (P=0.0001 versus Pit-1-dependent PA), Ngn2 expression was higher in secreting PA, especially in Pit-1-dependent PA (P=0.007 and P=0.0006 versus CNS respectively). Pit-1-dependent PAwhich received pre-operative pharmacological treatment expressed higher Ngn2 levels than untreated cases (P=0.025). Nuclear Ngn2 was observed in NP and in most PA, especially ACTH- and GH-secreting adenomas. Nuclear Ngn3 was observed in a minority of secreting PA. Ngn2 is normally expressed in the anterior pituitary and frequently expressed in PA, but does not account for NeuroD1 overexpression where present. Owing to their low and inconstant expression, the biological significance of Ngn1/3 in the adult pituitary is uncertain.