Serum somatomedin activity depressed after glucagon administration in man.

The variations in serum somatomedin (SM) activity were compared in 14 subjects after glucagon injection (1 mg im), and in 10 controls. A significant decrease in SM activity was observed 30 and 60 min after glucagon (p less than 0.01 to less than 0.001) whereas no significant change was noted in the controls. Analysis of the dose-response curves suggests that this decrease reflects depressed SM concentration. No correlation was found between the variations of growth hormone (GH), cortisol, or fatty acids and those of SM activity. The maximum variations in glycemia, insulin and SM activity occured during the same time interval. These results suggest that glucagon may play some role in the regulation of circulating SM.

Early paradoxical decrease in serum somatomedin activity following injection of growth hormone.

The early effects have been investigated of an intra-muscular growth hormone injection (6 mg/m2) on serum somatomedin activity in 21 children with growth hormone deficiency and in 5 children with constitutional short stature. In cases of hGH total deficiency, there was an early and significant decrease in SM activity, which reached a minimum level 2 hours after the injection (-34% p less than 0.01). After 24 hours, SM activity increased to +64% above basal levels. In cases of hGH partial deficiency and in short, non-hGH deficient children, no similar early changes were observed. Neither was any correlation found between the variations in SM activity and those in hGH or free fatty acid levels. The unexpected early decrease in SM activity following hGH administration seems to be related to GH deficiency.

Growth hormone response to thyrotropin-releasing hormone and oral glucose-loading tests in tall children and adolescents.

The effects of TRH and oral glucose loading on the release of GH were investigated in 10 children or adolescents with constitutional tall stature. Eight of these children had a family history of above average height. The mean (and SEM) baseline GH levels (3.12 +/- 2.0 ng/ml) were similar to those in control subjects. Somatomedin activity, measured by sulfate incorporation into chick embryo cartilage, was elevated. Oral glucose loading caused an early significant increase in plasma GH at 30 min in 2 of these subjects and a late rise at 180 min in 4 others. Intravenous injection of synthetic TRH (0.2 mg/m2) caused a marked increase in plasma GH (17 +/- 3.0 ng/ml) in 7 of the 10 patients; the peak of GH was observed within the first hour after the injection of TRH in 3 cases, while a later peak was observed in the second hour after injection in 4 others. Peak plasma PRL (47 +/- 3.8 ng/ml) and TSH (20 +/- 1.2 microU/ml) levels in response to TRH were normal. These results suggest a disorder of hypothalamo-pituitary regulation of GH secretion in certain children with apparently constitutional tall stature. Similar findings in a probably preacromegalic girl are reported.

Age-related variation in growth-promoting activity human plasma measured in human lymphocytes.

The age-related variations in the growth-promoting activity of human plasma have been studied from birth (cord blood) to adulthood using a bioassay which measures the incorporation of tritiated thymidine into lectin-activated human lymphocytes. Cord blood values were low (0.69 +/- 0.004 U/ml). A definite increase was found at 5 days of age, correlating with the level at birth. Higher levels were attained after 1 month of age, with a 2-fold increase during the first months of life. Lower values were found in children 1-10 yr old, and high levels were found during puberty. This pattern, different from those of sulfation activity and plasma somatomedins suggests that factors other than somatomedins may be involved in growth stimulation during the first year of life in humans.

Identification of neurotensin-related peptides in human thymic epithelial cell membranes and relationship with major histocompatibility complex class I molecules.

This study shows the expression at the cell surface of human thymic epithelial cells (TEC) of a neurotensin (NT)-like immunoreactivity. NT radio-immunoassay (RIA) revealed that cultured human TEC contain +/-5 ng immunoreactive (ir) NT/10(6) cells, of which 5% is associated with plasma cell membranes. HPLC analysis of NT-ir present in human TEC showed a major peak of NT-ir corresponding to NT1-13. NT-ir was not detected in the supernatant of human TEC cultures. Using an affinity column prepared with a anti-MHC class I monoclonal antibody, NT-ir-related peptides were retained on the column and eluted together with MHC class I-related proteins. According to the elution time on HPLC of these peptides, they correspond to intact NT1-13, as well as to smaller fragments of NT1-13.

Plasma neurotensin levels in humans: relation to hormone levels in diseases involving the hypothalamo-pituitary-thyroid axis.

This study was aimed to investigate, in humans, the possible relationship between plasma neurotensin (NT) levels and the activity of the hypothalamo-pituitary-thyroid axis. Neurotensin was measured by radioimmunoassay in 14 healthy adult volunteers and in 41 patients among whom 10 were considered as controls and 31 had thyroid dysfunction according to free thyroxine and thyrotropin plasma values. Basal NT levels were not significantly different in healthy adults and in control patients: 9.7 +/- 1.1 fmol/ml (mean +/- SEM) vs 13.3 +/- 2.9 fmol/ml, respectively. In patients with central hypothyroidism the NT level was significantly lower (5.7 +/- 1.2 vs healthy volunteers and controls; p < 0.05) and in patients with peripheral hypothyroidism and hyperthyroidism the NT level was significantly higher (35.9 +/- 12.8 and 29.9 +/- 9.5 fmol/ml, respectively, vs healthy adults (p < 0.01) and vs controls (p < 0.05)). After thyrotropin-releasing hormone (TRH) injection (250 micrograms iv) in nine subjects (two control patients, five patients with hypothyroidism and two patients with hyperthyroidism), NT levels decreased independently of the endocrine status from mean values of 13.4 +/- 8.4 at basal level to 7.3 +/- 0.8 fmol/ml 30 min after injection (p < 0.01 on paired percentage decrease values). These data suggest that plasma NT levels in humans depend upon the pituitary-thyroid status and indicate that TRH could exert a negative regulation on circulating NT levels.

Modulating effect of human growth hormone on tumour necrosis factor-alpha and interleukin-1beta.

We measured serum tumour necrosis factor-alpha (TNF-alpha) as well as interleukin-1betta (IL-1beta) and GH concentrations in 15 children with isolated growth hormone deficiency (GHD), age range 5.1-13.9 years, before and 4 and 24h after the first GH injection (0.1 IU/kg s.c.). No differences were found in basal concentrations of serum TNF-alpha and IL-1beta between GHD children (10.01 +/- 1.55 pg/ml and 2.14 +/- .16 ng/ml respectively) and sex- and age-matched controls (11.57 +/- 2.16 pg/ml and 3.78 +/- 1.46 ng/ml respectively). In GHD children, serum TNF-alpha and IL-1beta values had significantly increased (P < 0.002) 4h (26.75 +/- 5.57 pg/ml and 2.99 +/- 0.21 ng/ml respectively) and decreased again 24 h after GH administration. Likewise, serum GH levels had significantly increased 4 h (from 1.29 +/- 0.69 to 48.71 +/- 13.35 ng/ml, P < 0.001) and decreased to basal values 24h after GH administration. A significant correlation was found between basal serum concentrations of GH and those of both TNF-alpha (P < 0.01) and IL-1beta (P < 0.05). However, no correlation was found between serum GH concentration and either TNF-alpha or IL-1beta levels 4 and 24h after GH administration. Our data suggest that GH plays a role in modulating TNF-alpha and IL-1beta release in humans.

Developmental pattern of neurotensin content in rat hypothalamic neurons cultured in serum-free medium: comparison with in vivo data.

Neurotensinergic cells were visualized by immunocytochemistry in rat hypothalamic cultures grown in serum-free medium for 12 days. They represented 0.03% of the total cell population. The pattern observed for the evolution of neurotensin content in hypothalamic cultures, from day 5 to day 21 (7-fold increase), was similar to that observed in the rat hypothalamus during the corresponding period of in vivo ontogeny, from birth to 19 days postnatal (6-fold increase).

Plasma neurotensin levels in prepubertal children and adults: possible involvement in the regulation of growth hormone secretion.

The present study investigated a possible relationship between plasma neurotensin (NT) and serum growth hormone (GH) levels after GH-stimulation provocative tests in humans. Samples were obtained from twelve prepubertal children and sixteen normal adult volunteers. Basal plasma NT levels were higher in children with growth delay (19.02 +/- 4.01 fmol/ml) (mean +/- SEM) than in normal adults (6.13 +/- 1.1 fmol/ml) (p < 0.001). Basal GH levels in children (1.52 +/- 0.06 ng/ml) were not different from those in adults (0.60 +/- 0.41 ng/ml). After stimulation of GH secretion, NT values decreased when GH peaked, and increased when GH levels diminished. These data suggest that plasma NT levels may be involved in the regulation of GH secretion, as a peripheral signal, probably through modulation of somatostatin release from the median eminence.

Possible role of plasma neurotensin on growth hormone regulation in neonates.

OBJECTIVE: To evaluate secretion of plasma neurotensin (NT) which could be involved as a peripheral signal in growth hormone (GH) regulation, NT release was measured during early postnatal life, a period of striking changes in GH secretion. METHODS: Blood samples were collected from 19 normal full-term neonates on day 5 and at 3 months of age to evaluate plasma NT concentrations by radioimmunoassay, serum growth hormone (GH) levels using an immunofluorometric assay, and serum insulin-like growth factor-I (IGF-I) values by radioimmunoassay. RESULTS: Five day-old neonates showed significantly higher (p < 0.001) mean (+/- SEM) plasma NT levels (83.55 +/- 12.07 fmol/ml) compared with those in 11 prepubertal children and those in 14 adults who were studied as control subjects (13.30 +/- 2.90 and 9.70 +/- 1.10 fmol/ml, respectively). In 5 day-old neonates we observed significantly higher (p < 0.001) serum GH levels (29.53 +/- 3.40 ng/ml) compared with those in the prepubertal children (1.26 +/- 0.28 ng/ml). Five day-old neonates showed significantly lower (p < 0.001) serum IGF-I concentrations (27.01 +/- 0.77 ng/ml) than those in the prepubertal children (210 +/- 25 ng/ml). At 3 months of age, plasma NT levels (59.37 +/- 7.47 fmol/ml) and serum GH values (4.40 +/- 0.60 ng/ml) were significantly decreased (p < 0.001). At the 3rd month of life, serum IGF-I levels (44.88 +/- 4.30 ng/ml) were increased significantly (p < 0.001). CONCLUSIONS: The human neonate showed very high concentrations of NT and GH in comparison with those observed in control subjects. The postnatal rise in IGF-I values is presumed to determine the fall in serum GH concentrations by stimulating somatostatin secretion. Neurotensin could be involved as a peripheral signal in the inhibitory mechanisms mediated by release of somatostatin.

[Relationships between growth, and plasma growth hormone and growth factors under normal physiological conditions and during pathological states (author's transl)]. / Relations entre croissance, hormone de croissance et facteurs de croissance plasmatiques en physiologie et en pathologie.

Growth hormone (GH) and somatomedin (Sm) are the main factors of human growth. Sm is GH-dependent, but Sm increase after hGH injection in hypopituitary dwarfs is slow, and preceded by a decrease. The liver and kidneys are the main places of Sm production in vivo, the liver having probably also a regulatory effect. In vitro, GH-dependent production of Sm may be obtained from fibroblasts as well as from liver cells. Sm activates thymidine uptake by cultured human fibroblasts and by activated human lymphocytes, this effect needing cofactors from serum. Discrepant correlations between growth, GH and Sm are found in some pathological situations, such as obesity, craniopharyngioma, celiac disease, infantile malnutrition. Moreover, transferrin, a plasma protein, correlates also with growth.

[Measurement of tritiated thymidine incorporated into activated lymphocytes and of somatomedin activity in serum]. / Mesure de l'incorporation de thymidine tritiée dans le lymphocyte activé et activité somatomédine du sérum.

The authors describe a new technique of biological quantitative determination of the somatomedin activity in human plasma by incorporation of tritiated thymidine into human lymphocytes treated by specific activator. This method is more simple, faster, and more sensitive than the biological assays described so far.

Neonatal serum growth-promoting activity measured in human lymphocytes: comparison of cord and capillary blood.

The growth-promoting activity of serum was studied in 47 normal full-term newborns, comparing the effects of cord and of capillary serum upon the 3H-thymidine uptake into activated adult human lymphocytes. At birth the mean +/- SEM (TA) was significantly higher (P less than 0.001) in capillary serum (1.26 +/- 0.08 U/ml) than in cord blood (0.88 +/- 0.05 U/ml), the individual values being significantly correlated. The relatively low values in cord blood do not result from the presence of an inhibitor, nor from the cortisol levels. It may be concluded that study of cord blood is not the best means to measure growth-stimulating factors in newborns.

Production of interleukin-1-alpha and interleukin-2 by mononuclear cells in healthy adults in relation to different experimental conditions and to the presence of growth hormone.

Several reports support the view that the growth hormone (GH) possesses a number of important immunomodulatory properties. This study was undertaken to determine in vitro the role of the GH on interleukin (IL) production. Cultures of blood peripheral lymphocytes obtained from human normal adults were performed in RPMI medium in the presence or absence of phytohemagglutinin (PHA), heated normal serum (NHS) 1% and GH 12.5-500 microgram/l. After incubation from 15 h to 4 days at 37 degrees C in a humidified atmosphere containing 5% CO2, cells were discarded and the supernatants were tested for their contents of IL-1 alpha and IL-2 measured using the Amersham radioimmunoassay system. The results of these in vitro experiments show that: (1) the bulk cultures from peripheral lymphocytes are suitable to study the IL-1 and IL-2 production; (2) in optimal conditions for IL production (incubation during 48 h in the presence of PHA and NHS) no effect of GH was observed on IL production; (3) in the absence of PHA GH acts at physiological doses (less than 100 ng/ml) by increasing the IL production. This effect of GH was optimized with a short time of incubation (16 h) and in the simplest conditions of cultures, that is to say in the absence of serum and of PHA: thus in the presence of GH 100 ng/ml the IL-1 production increases from 0.53 to 3.86 fmol (tubes) and IL-2 increases from 0.18 to 3.22 fmol (tubes). These differences are significant (p less than 0.001). We conclude that GH acts in vitro on mononuclear cells to induce IL production.

In vitro effect of human growth hormone on lymphocyte transformation and lymphocyte growth factors secretion.

Cultures of human blood peripheral lymphocytes were performed in the presence or absence of human growth hormone, and also of phytohemagglutinin and normal human serum 10%. After incubation for 48 h, the supernatants were tested for their ability to promote the uptake of [3H]thymidine into lectin-activated lymphocytes. Supernatants from lymphocyte-free control samples, treated in the same manner, were assayed under the same experimental conditions. Variance analysis of the different dose-response relationships was performed. The results of these in vitro experiments confirm that physiological levels of GH inhibit the lectin-induced lymphoproliferation and that lymphocytes secrete an 'activity' able to stimulate the incorporation of [3H]thymidine into lectin activated lymphocytes. Furthermore we show that: 1) Secretion of this lymphocyte-stimulating activity is increased by physiological levels of GH; 2) This lymphocytic secretion is not radioimmunoassayable IGF-I; 3) Using fast protein liquid chromatography (FPLC), this activity appears in fractions with various molecular weights.

A hormonally controlled serum factor stimulating the thymidine uptake into lectin-activated lymphocytes.

The in vitro stimulation of [3H]thymidine uptake into lectin-activated lymphocytes in the presence of various sera was studied. The mean precision of the assay is 5%, and the study of the confidence intervals shows variations from 4% to 12%. Compared to a normal reference serum (fixed as 1 U/ml), the serum thymidine uptake stimulating activity (mean +/- SEM) was 1.04 +/- 0.07 U/ml in normal adult males, 2.63 +/- 0.48 U/ml in acromegalic patients, 1.51 +/- 0.13 U/ml in constitutional dwarfism and 0.37 +/- 0.04 U/ml in untreated hypopituitary dwarfism with a significant difference between the groups (P less than 0.001). In patients with hypopituitarism a single im hGH dose (6 mg/m2 increased the thymidine uptake stimulating activity of serum within 24 to 48 h following injection. The effects of directly adding hGH, insulin and T3 to the assay, have been studied: pharmacological concentrations are required to produce only a slight effect. Physiological concentration of a purified preparation of somatomedin A stimulated thymidine uptake and its effect is increased in the presence of serum. These data demonstrate that [3H]thymidine uptake into lectin-activated lymphocytes is stimulated by a GH-dependent serum factor. The data suggest that this method should be proposed for an accurate and sensitive biological evaluation of serum thymidine uptake stimulating activity.

[Interference of liquemine with plasma somatomedin activity]. / Interférence de la liquémine sur l'activité somatomédine du plasma.

Experimental conditions for preparation of plasma and the interference of the heparin (liquemine) on the somatomedin bioassay were studied. Results showed the significant inhibitory effect of liquemine, increasing with the delay before centrifugation, on the interpretation of the results of the assay.