Human Fetal Pituitary Glands Research Articles

Assessment of ghrelin, GHS-R, GH, and neurohormones in human fetal pituitary glands and central nervous system: an immunohistochemical study.

The aim of this work was evaluation of expression of ghrelin and GHS-R1a receptor in somatotrops and in neuronal cells of brain tissue in the process of human fetal ontogenesis. Relations were also looked for between GHRH and SS in the pituitary and in the CNS neurones of the studied fetuses. The study was based on 8 pituitaries and 8 brains from fetuses in different periods of intrauterine life. The immunocytochemical technique was used. The presence of ghrelin, GHS-R was shown in the glandular part of the pituitary and CNS during the whole period of intrauterine life. Neurohormones in the stalk of the pituitary were found in fetuses from the 32nd week of pregnancy whereas in the CNS neurones these hormones could be detected throughout the whole period of intrauterine life. The results obtained suggest that stimulation of GH secretion by ghrelin is independent of the feedback concentration and these two hormones act like signals of metabolic balance. GH release by ghrelin in fetal life is independent of somatostatin. The hypothalamic-pituitary axis which regulates pulsatile GH release from the pituitary matures functionally in the third trimester of pregnancy independent of the previous anatomical differentiation.

Organisation of basement membrane components in the human adult and fetal pituitary gland and in pituitary adenomas.

Cell-matrix interactions undoubtedly have a role in the development and maintenance of the complex nonrandom structure of the human pituitary gland. We have extended previous studies by documenting the patterns of immunoreactivity for type IV collagen, laminin and fibronectin in the fetal gland, comparing these with the adult patterns. In both we have examined the differences between the anterior lobe and intermediate zone in an attempt to elucidate the apparent differences in functional response between corticotrophs in the two areas. We have also examined expression of these proteins in a series of pituitary adenomas. Finally, we have immunolocalised beta 4 integrin, a component of the alpha 6 beta 4 laminin receptor, in the adult gland and in adenomas. In the anterior lobe of the adult gland, type IV collagen and laminin were present in both epithelial and vascular basement membrane. Fibronectin was related to the basement membrane but showed a less continuous distribution. beta 4 Integrin was expressed on the basal aspects of pituitary cells, in association with laminin, suggesting that this did identify the alpha 6 beta 4 laminin receptor. In addition, immunoreactivity was present on the lateral margins of some pituitary cells, which might indicate a role in cell-cell adhesion. None of the proteins showed specific association with any particular cell type, suggesting that these specific interactions do not regulate differentiation. This pattern of expression had developed in the fetal gland by the second trimester, with expression relating to vessels preceding that in epithelial basement membrane. Type IV collagen, laminin and fibronectin were also expressed in epithelial and vascular basement membrane in the intermediate zone of the adult gland, and around Rathke's cleft in the fetal gland. However, the organisation differed, with larger groups of cells enclosed within a single basement membrane. Possible vascular connections demonstrated between the posterior lobe and the intermediate zone would permit access of posterior lobe hormones to this zone. Our data confirmed disruption of expression in pituitary adenomas, type IV collagen, laminin and beta 4 integrin having a mainly perivascular distribution, with more variable immunoreactivity for fibronectin.

The ontogeny of pit-1 expression in the human fetal pituitary gland.

Pit-1 expression has been reported to be cell-type-specific in the adult human pituitary and in human pituitary adenomas. In contrast, studies of rodent fetal adenohypophysial development as well as mature rodent glands have indicated that the pit-1 mRNA is ubiquitously expressed and the protein is under translational control. To determine the ontogeny and localization of Pit-1 expression in the human fetus, we examined fetal pituitaries (n = 23) at various stages of gestation from 6 weeks to term using in situ hybridization (ISH) for pit-1 mRNA, immunohistochemical localization of Pit-1 protein, and combined ISH for pit-1 mRNA with immunohistochemistry for pituitary hormones. At 6 and 7 weeks of gestation, the cells surrounding both limbs of Rathke's cleft showed a moderate specific signal for pit-1 mRNA. At 7 weeks, only a few cells were immunoreactive for ACTH and there was no definite colocalization of that hormone with pit-1 mRNA. At 8 and 9 weeks of gestation, there was definite preferential expression of pit-1 mRNA in cells containing growth hormone (GH) but not ACTH, as well as in cells with no detectable hormone immunopositivity. At midgestation and after, there was clear correlation between pit-1 mRNA expression and hormone content; cells with GH, prolactin and/or thyrotropin immunoreactivity had abundant pit-1 mRNA, whereas those containing ACTH, FSH or LH were negative for pit-1 mRNA by ISH and its protein by immunohistochemistry. The signal for pit-1 mRNA was stronger in intensity and present in more cells in fetal than in adult adenohypophyses. The ontogeny of pit-1 mRNA expression indicates that it precedes the onset of pituitary hormone detection. Its abundance in the human pituitary early in gestation may reflect its role in cytodifferentiation and cell proliferation. The correlation between pit-1 mRNA detection and Pit-1 protein localization is consistent with a cell-type-specific pretranslational regulatory mechanism for Pit-1 expression in the developing human adenohypophysis.

Immunoelectron microscopic study of the GH cell in the anterior pituitary gland of normal human fetus.

Ultrastructural studies of growth hormone-producing cells (GH cells) in the anterior pituitary gland have been reported using several experimental animals. However, no attempt has yet been made to identify the ultrastructural heterogeneity of the GH cells within the human anterior pituitary gland. To this end, we employed immunogold electron microscopy to investigate the ultrastructural characteristics of GH cells in relation to gestational age in normal human fetuses. Based on ultrastructural characteristics, three distinct types of GH cells were identified by immunogold electron microscopy in the anterior pituitary glands of 34 normal human fetal pituitary glands. The age of the tissue samples ranged from 8 to 34 weeks. The Type-I GH cell is a small, round cell with a narrow cytoplasm containing a few small secretory granules (268 nm in mean diameter). The GH cells designated Type-II are polygonal and contain medium-sized secretory granules (347 nm), profiles of rough endoplasmic reticulum (RER) arranged in parallel lamellae, and a Golgi complex which is frequently encountered but only in this cell type. The Type-III GH cell is polygonal, large, and contains numerous large spherical-shaped secretory granules (404 nm). The Type-I was the predominant cell type until about 20 weeks of gestation; its incidence decreased thereafter. In contrast, the Type-II and Type-III cells increased in number starting at 20 weeks of gestational age. From these results, we suggest that Type-I is the most immature type of GH cell, Type-III the most mature, and the Type-II is intermediate in development. The marked difference in the incidence of each GH cell type between the first and second half of gestation appears to be a reflection of the development of the hypothalamic regulation of the anterior pituitary gland, which is reported to be established at around 20 weeks of gestation.

In vitro modulation of growth hormone (GH) secretion from early to midgestation human fetal pituitaries by GH-releasing factor and somatostatin: role of Gs-adenylate cyclase-Gi complex and Ca2+ channels.

Using explant cultures of human fetal anterior pituitary glands (9-19 weeks fetal age) and an acute (3-h) test protocol, we investigated the role of two signal transduction pathways (Gs-adenylate cyclase-Gi, Ca2+ channels) in GH-releasing factor (GRF)/somatostatin (SRIF) regulation of GH secretion during the first half of gestation. Data have been analyzed for ontogenic changes using three age groups: 9-10, 12-13, and 15-19 weeks fetal age. The fetal somatotrope shows dose-related responses to forskolin (0.1-10 microM), dibutyryl cAMP (dBcAMP; 0.1-1 mM), and theophylline (0.01-1 mM), all factors that increase intracellular concentrations of cAMP; there is a significant age-related increase in the stimulatory effects of 1 mM dBcAMP and 1 mM theophylline. When any one of these three factors is added with 10 nM GRF, there are no significant additive or synergistic effects on GH secretion. Although 10 nM SRIF has no effect at 9-10 weeks, it is inhibitory in the 12-13 and 15-19 week groups, significantly suppressing the stimulatory effect of 1 microM forskolin and completely blocking the effects of 1 mM dBcAMP or theophylline. Pretreatment of cultures with pertussis toxin completely blocks SRIF inhibition of both basal and GRF-stimulated GH release. KCl (5-50 mM) and Bay K 8644 (0.1-10 microM), both activators of Ca2+ channels, have dose-related stimulatory effects on GH release; 50 mM KCl shows an age-related increase in stimulatory activity. If 10 nM GRF, 1 microM forskolin, 1 mM theophylline or 1 mM dBcAMP is added with either 50 mM KCl or 1 microM Bay K 8644, there is an additive response. SRIF (10 nM) completely blocks the stimulatory effects of 1 microM Bay K 8644 and markedly inhibits the effects of 50 mM KCl from as early as the ninth week of fetal age. The Ca2+ channel blocker nifedipine (1-10 microM) significantly inhibits basal as well as stimulated (GRF, forskolin, dBcAMP, theophylline, KCl, and Bay K) GH release from as early as 9 weeks fetal age; in contrast, the calmodulin blocker trifluoperazine (0.01-10 microM) has no effects on basal GH secretion and only slightly inhibits the stimulatory effects of KCl. Pretreatment with 10 nM GRF for 24 h significantly decreases a subsequent 3-h response to 10 nM GRF, but does not alter the subsequent response to 1 mM theophylline or 50 mM KCl.(ABSTRACT TRUNCATED AT 400 WORDS)

Human fetuin/alpha 2 HS glycoprotein in colloid and parenchymal cells in human fetal pituitary gland.

An immunohistochemical study was undertaken, in an attempt to identify the acidic glycoprotein(s) present in colloid and in parenchymal cells in human fetal pituitary gland. As the colloid has been proposed to represent disintegrating cells, a series of antibodies against plasma glycoproteins and plasma proteins was applied; their presence intracellularly would generally be an indicator of plasma membrane leakage in dying parenchymal cells. In tissue sections from 9- to 20-week-old fetuses, the colloid showed prominent staining with an antibody to human fetuin/alpha 2 HS glycoprotein. Anti-alpha 2-HS glycoprotein labelled parenchymal cells in pars anterior and intermedia. Apart from a minor immunoreactivity for alpha 1 beta glycoprotein, no other plasma glycoprotein was seen in colloid or parenchymal cells. An antibody against bovine fetuin showed staining of the colloid and of some parenchymal cells in pars distalis and intermedia; the plasma and stroma of the pituitary gland were unstained. In contrast, the anti-human plasma protein antibodies all stained the stroma. The presence of alpha 2 HS glycoprotein in parenchymal cells and absence of other plasma glycoproteins imply integrity of the parenchymal cell plasma membrane. Thus, alpha 2 HS glycoprotein is either synthesized locally or taken up specifically in the parenchymal cells, which are proposed to participate in the formation of colloid. It is suggested that alpha 2 HS glycoprotein is part of a homeostatic system, which controls remodelling and physiological cell death during development.

Presence of Acetylated and Shortened Endorphins in Human Fetal Pituitary Gland

A total of 21 human fetal pituitaries was collected from spontaneous abortions (11 cases) or prostaglandin (PG)-induced abortions at the second trimester. Pituitaries were homogenized, fractionated by HPLC, and the fractions were tested by specific RIA for alpha-endorphin (EP) (beta-EP 1-16), gamma-EP (beta-EP 1-17), beta-EP (beta-EP 1-31), and their alpha-N-acetylated derivatives. In the fetal pituitaries collected after spontaneous abortion, the contents of alpha-EP (23.4 +/- 7.5 pmol/mg protein, mean +/- SE) and gamma-EP (28.9 +/- 9.7) were similar to those of beta-EP (28.6 +/- 7.4). Both beta-EP/alpha-EP (1.2 +/- 0.3) and beta-EP/gamma-EP (1.1 +/- 0.3) ratios approached unity. Although 35.7 and 30.2% of alpha-EP and gamma-EP were acetylated, acetyl-beta-EP was only 8.4% of the total beta-EP immunoreactivity. In the five cases of PG-induced abortion that were more than 20 wk of pregnancy, the pituitary content of beta-EP (75.9 +/- 21.2) and gamma-EP (26.2 +/- 7.5) were significantly higher than in samples collected after spontaneous abortion (13.3 +/- 8.2 and 5.9 +/- 1.8, respectively, p less than 0.01). On the contrary, neither alpha-EP (31.3 +/- 5.2), acetyl-alpha-EP (0.94 +/- 0.28), acetyl-gamma-EP (0.65 +/- 0.07), acetyl-beta-EP (0.35 +/- 0.05) pituitary contents in PG-induced abortions differed from those measured after spontaneous abortion (alpha-EP: 25.6 +/- 6.6; acetyl-alpha-EP: 0.92 +/- 0.41; acetyl-gamma-EP: 0.82 +/- 0.30; acetyl-beta-EP: 0.96 +/- 0.44).(ABSTRACT TRUNCATED AT 250 WORDS)

Hormone production and peptide regulation of the human fetal pituitary gland.

Introduction THE PREVALENT view of the ontogeny of neuroendocrine regulation of anterior pituitary secretion promulgated by Gluckman et al. (1), in an earlier review in this journal is that the development of this control is dependent upon maturation of the central nervous system. But by the time the central nervous system completes its synaptogenesis and other integrative systems of the developing human have reached a state of maturity competent to perform many of the tasks associated with homeostasis, the endocrine system will have been functional for some time. Thus, the endocrine system may be perceived not as mimicking that of the adult, but rather as one of the first, if not the first, homeostatic systems to develop, a system which is functional from intrauterine life through old age, but which may have unique functions during fetal life. As will be shown, the neuroendocrine axis appears early in fetal development, and the full repertoire of neurotransmitter, neuropeptide, and hormonal factors are a...

Hypophysiotropic and neuromodulatory regulation of adrenocorticotropin in the human fetal pituitary gland.

Synthetic human corticotropin-releasing factor (hCRF) stimulated ACTH secretion by human fetal pituitaries in superfusion and dispersed human fetal pituitary cells cultured on an extracellular matrix in static incubation from 14 to 23 wk gestational age. The action of hCRF in vitro was potentiated by arginine vasopressin (AVP) at all ages studied. 8-Br-cAMP induced a response similar to hCRF. The AVP effect on ACTH was synergistic with both CRF and 8-Br-cAMP. hCRF-mediated secretion of ACTH was noncompetitively inhibited by 24-h pretreatment, or by 3-h concomitant treatment, with dexamethasone. Neither oxytocin, catecholamines, prostaglandins, nor indomethacin exerted significant effects on ACTH secretion, either alone or in combination with hCRF or AVP during the gestational ages studied. These results support a physiologic role for CRF in the regulation of secretion by corticotropic cells as early as 14 wk gestation, by which time corticotropes and ability to secrete ACTH have been demonstrated.

Corticotrophin-releasing factor-like immunoreactivity and bioactivity of human fetal and adult hypothalami.

Corticotrophin releasing factor-like immunoreactivity (CRF-LI) and bioactivity, and arginine vasopressin-like immunoreactivity (AVP-LI) have been measured in extracts of human fetal and adult hypothalamic tissue and their development with the gestational age of the fetuses (12-27 weeks) studied. CRF-LI was measured by a radioimmunoassay developed for ovine corticotrophin-releasing factor (oCRF-41). Corticotrophin-releasing factor bioactivity was measured in a rat isolated anterior pituitary cell perfusion system. CRF-LI and bioactivity and AVP-LI were all detectable in fetal hypothalamic extracts from 12 to 13 weeks of gestational age. CRF-LI was also present in human fetal pituitary glands from 12 weeks of gestational age. The concentration of CRF-LI in the fetal hypothalamic extracts (9.2 +/- 11.4 ng/g, mean +/- S.E.M., n = 33) showed no significant correlation with the gestational age of the fetuses. However the concentration of AVP-LI (25.0-36.8 ng/g, n = 17) did show a positive correlation (r = 0.508, P less than 0.05) with gestational age, as did the concentration of CRF bioactivity (471.3-556.3 ng ACTH released/g tissue, n = 13, r = 0.725, P less than 0.01). The CRF bioactivity of all fetal hypothalamic extracts was potentiated by the addition of synthetic human (h)AVP, but the bioactivity of the adult hypothalamic extracts was not, presumably because of the higher levels of AVP-LI already present in the adult extracts. Pretreatment of tissue extracts with antisera to oCRF-41 and/or hAVP reduced the CRF bioactivity of all hypothalamic extracts. Sephadex chromatography of fractions which co-eluted with synthetic oCRF-41 or hAVP contained CRF bioactivity and this bioactivity was potentiated when synthetic hAVP or oCRF-41, respectively, were added to the fractions. However, a larger molecular weight form of CRF-LI (8000-10 000 daltons), which was observed only in fetuses of 20 weeks of gestational age or less, did not contain any significant CRF bioactivity.

Human fetal adenohypophysis. Histologic and immunocytochemical analysis.

One hundred and forty human fetal pituitary glands were removed from fetuses at 7-40 weeks of gestation and studied by light microscopy and immunocytochemistry to localize adenohypophysial hormones. For immunocytology, the avidin-biotin-peroxidase complex technique was more sensitive and identified hormones in younger fetuses than did the immunoperoxidase method. Adrenocorticotrophin, beta-endorphin, and growth hormone were the first hormones detected; they were identified by intense cytoplasmic immunopositivity at 8 weeks of gestation. Between 10 and 20 weeks, many growth hormone containing cells were large and showed scattered, faint positivity; after 20 weeks, smaller cells with intense positivity predominated. alpha-Subunit of the glycoprotein hormones was identified at 9 weeks of development; beta-subunits of thyroid-stimulating hormone, follicle-stimulating hormone, and luteinizing hormone appeared by 12 weeks. Gonadotrophs differed in numbers related to fetal age and sex. From 15 to 25 weeks, glands of female fetuses contained more gonadotrophs than did those of males; after 25 weeks, there was no significant difference in total gonadotroph numbers. Throughout gestation, adenohypophyses of male fetuses had more luteinizing hormone containing cells than follicle-stimulating hormone containing cells; pituitaries of females had approximately the same numbers of follicle-stimulating hormone containing and luteinizing hormone containing cells. Prolactin was identified in few small cells at 12 weeks; at term, prolactin-containing cells were numerous, comparable to those seen in the hyperplasia of maternal glands in late gestation and during lactation. This comprehensive study indicates morphologic correlations with pituitary hormone extraction data and with the appearance of the various hormones in the fetal circulation.

Light and electron microscopic localization of the N-terminal fragment of human pro-opiomelanocortin in the human pituitary gland and in neoplasms.

Immunohistochemical localization of the N-terminal fragment (1-76) (NTF) of human pro-opiomelanocortin (POMC) was studied in human adult and fetal pituitary glands, as well as in pituitary adenomas associated with Cushing's syndrome and in ectopic ACTH-producing tumors. Comparison of localization between NTF and ACTH was performed using mirror sections. Our results indicated concomitant localization of NTF and ACTH in the same cells, not only in normal adult and fetal pituitaries but also in pituitary adenomas and ectopic ACTH producing tumours. Specificity of the NTF staining was confirmed by immunoabsorption. Negative staining of the bovine pituitary gland indicated the immunohistochemical localization of N-terminal (1-45) of human POMC as there is a known species difference in the sequence 1-45 between human and the bovine N-terminal fragment. Presence of NTF in cisterna of rough endoplasmic reticulum indicates its production by small cell carcinoma. These findings, together with the previous studies, suggest that the complete form of POMC is produced in the tumours as well as in normal pituitaries.

Light and electron microscopic localization of ACTH and pro-opiomelanocortin-derived peptides in human developmental and neoplastic cells.

Oncofetal aspects of ACTH and pro-opiomelanocortin (POMC)-derived peptides were studied immunohistochemically at the light and electron microscopic level in human fetal pituitary glands, pituitary adenomas, and small-cell carcinoma of the lung. ACTH, beta-endorphin, and gamma-MSH were localized in the same cells of both fetal and adult pituitary, as well as in the above-mentioned neoplastic tissues. However, alpha-MSH was observed only in the early fetal pituitary, its concentration decreasing with advancing gestational age. The adult pituitary contained only a few alpha-MSH-positive cells. By immunoelectron microscopy, ACTH in the adult pituitary was localized exclusively in the secretory granules. In fetal pituitary at 9 weeks' gestation, ACTH was localized in the perinuclear spaces (PNS), cisternae of rough endoplasmic reticulum (RER), Golgi saccules, and secretory granules. The staining pattern of ACTH in these organelles varied from cell to cell. In fetal pituitaries of greater gestational ages, ACTH was localized in secretory granules. The pituitary adenomas mimicked the staining characteristics of the adult pituitary, i.e., negative or only very occasional alpha-MSH staining and localization of ACTH in the secretory granules. The ectopic ACTH-producing tumors showed a staining pattern similar to that of the early fetal pituitary, i.e., positive staining for alpha-MSH and the presence of ACTH in PNS and cisternae of RER.

Effects of Synthetic Corticotropin-Releasing Factor and Dopamine on the Release of Immunoreactive β-Endorphin/β-Lipotropin and α-Melanocyte-Stimulating Hormone from Human Fetal Pituitariesin Vitro*

The effects of synthetic corticotropin-releasing factor (CRF) and dopamine on immunoreactive beta-endorphin/beta-lipotropin (i beta-END/LPH) and alpha MSH release were studied in superfused human fetal pituitary glands. CRF (20 ng) stimulated the release of i beta-END/LPH in four anterior hemipituitaries from fetuses older than 20 weeks in gestation. There was no effect on three anterior hemipituitaries from fetuses of 19-20 weeks gestation. CRF had no effect on i beta-END/LPH or alpha MSH secretion from neurointermediate lobes regardless of fetal age. Dopamine (10(-6) M) had no effect on i beta-END/LPH or alpha MSH secretion from either anterior or neurointermediate lobes. The data suggest that anterior pituitary responsiveness to CRF develops at about 20 weeks gestation and that fetal neurointermediate lobe secretion of peptides is not regulated by CRF.

Levels of alpha-melanotrophin in the human fetal pituitary gland throughout gestation, in adult pituitary gland and in human placenta.

alpha-Melanotrophin was detected by radioimmunoassay in the human fetal pituitary gland from 11 weeks of gestation. The peak hormone concentration of 3.4 nmol/g pituitary tissue was reached at 17-20 weeks. From 17 to 36 weeks of gestation the total gland content rose gradually from 28 to 102 pmol. During this latter period, the pituitary gland grew some 10-fold, with the result that the alpha-melanotrophin concentration declined steadily to 1.3 nmol/g. In the final month of gestation, both the total gland content and the concentration of alpha-melanotrophin rose significantly to 254 pmol and 2.4 nmol/g respectively. The variations in pituitary gland content of alpha-melanotrophin were consistent with a role for pars intermedia peptides in the fetus. alpha-Melanotrophin-like peptides were not demonstrated in human placental tissue.

Functional differentiation of cells in the anterior and intermediate pituitary glands - Immunohistochemical studies.

Immunohistochemical studies have demonstrated that in the adult rat and human anterior pituitary glands that one cell might be devoted to the production of one hormone with the exception of FSH and LH. In addition, the intermediate lobe cells are exclusively positive for ACTH. In studies of rat and human fetal pituitary glands, ACTH was the first hormone to appear in both anterior and intermediate cells, followed by other hormone-producing cells. As the hypothalamic tropic hormones appear later than the corresponding pituitary hormones, it was considered that the pituitary cells might differentiate toward hormone production independently of the hypothalamus and that hypothalamic tropic factors might be necessary to maintain or promote hormone production. This is supported by studies on human anencephalic pituitaries and cultured rat pituitary primordial cells.

The major immunoreactive alpha-melanocyte-stimulating hormone (alpha MSH)-like substance found in human fetal pituitary tissue is not alpha MSH but may be desacetyl alpha MSH (adrenocorticotropin1-13NH2).

Pituitary glands were obtained from human abortuses during the second half of gestation. Acid extracts were made from the anterior and neurointermediate lobes, and alpha MSH immunoreactivity (alpha MSHi) was quantified by RIA. alpha MSHi was found in both lobes of the pituitary gland, with 20-80% of the total pituitary alpha MSHi being present in extracts of the anterior lobe. Anterior and neurointermediate lobe extracts subjected to gel filtration on Sephadex G-50 revealed one peak of alpha MSHi having an elution profile identical to those of alpha MSH and desacetyl alpha MSH (ACTH1-13NH2). To characterize further the alpha MSHi extracts were subjected to high pressure liquid chromatography. No alpha MSH could be identified in extracts of the anterior lobe, and most of the alpha MSHi had an elution profile identical to that of desacetyl alpha MSH. Although small amounts of alpha MSH might be present in the neurointermediate lobe, most of the alpha MSHi in this lobe coeluted with desacetyl alpha MSH. Since alpha MSH was not converted to desacetyl alpha MSH during the extraction and chromatographic procedures, we hypothesize that the predominant form of alpha MSH-like material in the human fetal pituitary gland may be desacetyl alpha MSH.

Fetal neurohypophyseal arginine vasopressin and arginine vasotocin in man and sheep.

Immunoreactive arginine vasopressin (AVP) and arginine vasotocin (AVT) were quantitated in 15 of 17 human fetal pituitary glands early in gestation (11-19 weeks) and in 8 of 9 ovine fetal pituitary glands late in gestation (109-137 days). In 14 of 15 human fetal glands, AVT content exceeded that of AVP. There was a significant rise of AVP (as a percentage of total AVP plus AVT content) with gestational age over the period of 12-19 weeks (P less than 00.01). The ovine fetal glands demonstrated a preponderance of AVP over AVT. The mean AVP and AVT content in the ovine glands was 5.7 +/- 2.9 and 0.8 +/- 0.2 mU/mg gland weight, respectively, compared with the values in the human fetal pitiutaries, 0.8 +/- 0.2 and 1.2 +/- 0.2 mU/mg gland weight, respectively. The relative percentage of AVP and AVT in the ovine fetal pituitaries was 76.0+/- 9.6% and 23.9 +/- 9.6%, respectively, as contrasted to the human fetal glands, 36.7 +/- 2.7% AVP and 63.3 +/- 2.7% AVT. The preponderance of AVT over AVP in the early gestational age mammalian fetus may represent a primative first step in molecular evolution of the neurohypophyseal peptides.

THE RELEASE OF TSH FROM ORGAN CULTURES OF HUMAN FETAL PITUITARY GLANDS

It is known that the fetal human pituitary gland starts producing proteohormones in the 5th week of gestation (Siler et al., 1971). Thyreotropin (TSH) was detected in anterior pituitary tissue after the 12th week of gestation (Fukuchi et al., 1970). We studied the TSH release from long-term organ cultures of human fetal pituitary glands and its response to synthetic thyreotropin releasing-factor (TRF) and triiodothyronine (T3).

The ontogenesis of human fetal hormones. I. Growth hormone and insulin.

The content and concentration of immunoreactive growth hormone (GH) were measured in 117 human fetal pituitary glands from 68 days of gestation to term and in the pituitary glands of 20 children 1 month to 9 yr of age. Physicochemical and immunochemical properties of GH of fetal pituitary glands and GH from adult pituitary glands were indistinguishable by disc gel electrophoresis, immunoelectrophoresis, starch gel electrophoresis, and radioimmunoassay techniques. In the fetal pituitary gland, the GH content rose from mean levels of 0.44+/-0.2 mug at 10-14 wk of gestation, to 9.21+/-2.31 mug at 15-19 wk, to 59.38+/-11.08 mug at 20-24 wk, to 225.93+/-40.49 mug at 25-29 wk, to 577.67+/-90 mug at 30-34 wk, and to 675.17+/-112.33 mug at 35-40 wk. There was a significant positive correlation between growth hormone content of the pituitary and gestational age, crown-rump length, and the weight of the pituitary gland. The content and concentration (micrograms/milligram) of human growth hormone (HGH) in the fetal pituitary showed significant increments (P < 0.001) for each 4 wk period of gestation until 35 wk. Further increases in the HGH content were noted in pituitaries of children aged 1-9 yr (range of 832 to 11.211 mug). Immunoreactive GH was detected in fetal serum at a concentration of 14.5 ng/ml as early as 70 days gestation, the youngest fetus assayed. At 10-14 wk, the mean concentration of serum growth hormone was 65.2+/-7.6 ng/ml; at 15-19 wk 114.9+/-12.5 ng/ml; at 20-24 wk 119.3+/-19.8 ng/ml; at 25-29 wk 72.0+/-11.5 ng/ml; and 33.5+/-4.2 ng/ml at term. A significant negative correlation of serum growth hormone with advancing gestational age after 20-24 wk was observed (P < 0.001). In 17 fetuses paired serum and pituitary samples were assayed; no significant correlation between the concentration of serum GH and the pituitary content or concentration of GH was demonstrable. The serum concentration of chorionic somatomammotropin (HCS) in the fetus was unrelated to gestational age. Insulin (1-30 muU/ml) was detected in 42 of 46 fetal sera assayed. These data suggest that the appearance and development of the secretory capacity for GH by the human fetal pituitary gland coincides with developmental changes in the portal system and hypothalamus. Maturation of inhibitory central nervous system control mechanisms for secretion of GH may not occur until infancy.