Impact of oncogenes in tumor angiogenesis: Mutant K-ras up-regulation of vascular endothelial growth factor/vascular permeability factor is necessary, but not sufficient for tumorigenicity of human colorectal carcinoma cells

Targeted disruption of the single mutant K-ras allele in two human colorectal carcinoma cell lines (DLD-1 and HCT-116) leads to loss of tumorigenic competence in nude mice with retention of ability to grow indefinitely in monolayer culture. Because expression of the mutant K-ras oncogene in these cell lines is associated with marked up-regulation of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF), we sought to determine whether this potent angiogenesis inducer plays a role in K-ras-dependent tumorigenic competence. Transfection of a VEGF₁₂₁ antisense expression vector into DLD-1 and HCT-116 cells resulted in suppression of VEGF/VPF production by a factor of 3- to 4-fold. The VEGF/VPF-deficient sublines, unlike the parental population or vector controls, were profoundly suppressed in their ability to form tumors in nude mice for as long as 6 months after cell injection. In contrast, in vitro growth of these sublines was unaffected, thus demonstrating the critical importance of VEGF/VPF as an angiogenic factor for HCT-116 and DLD-1 cells. Transfection of a full-length VEGF₁₂₁ cDNA into two nontumorigenic mutant K-ras knockout sublines resulted in a weak but detectable restoration of tumorigenic ability in vivo in a subset of the transfectants, with no consistent change in growth properties in vitro. The findings indicate that mutant ras-oncogene-dependent VEGF/VPF expression is necessary, but not sufficient, for progressive tumor growth in vivo and highlight the relative contribution of oncogenes, such as mutant K-ras, to the process of tumor angiogenesis.     

The effect of antibody against vascular endothelial growth factor on tumor growth and metastasis

Vascular endothelial growth factor (VEGF), a very important in the process of tumor angiogenesis, was chosen as a target in a study to determine whether manipulation of angiogenesis with antibody against VEGF may interrupt tumor growth and metastasis. Anti-VEGF antibody was obtained from immunized rabbits, purified on an affinity column, and identified as neutralized antibody by Mile's assay. IVTA₂MA891, a murine spontaneous breast cancer with a high rate of metastasis in lung in TA₂ × 615 F1 mice, was chosen as an animal model in this study, because of the high expression of VEGF in the primary tumor as well as in the lung metastatic tumor. The anti-VEGF antibody could inhibit growth of S180 sarcoma in a dose-dependent manner, and the inhibition rate could reach 41.0% with a dose of 200 μg mouse⁻¹ day⁻¹. Anti-VEGF antibody could inhibit tumor growth by 76.2% in nude mice bearing human gastric cancer (MGC 803). When anti-VEGF antibody was combined with ¹³¹I-3H11, a murine monoclonal antibody conjugated with ¹³¹I, only one of five nude mice developed tumor and 84.0% more inhibition of tumor growth was obtained in comparison with treatment by ¹³¹I-3H11 alone. The growth of the primary tumor was inhibited by 44.0% and the number and size of the metastatic foci in the lungs were reduced by 73.0% and 83.7% respectively in the animal model, with a high rate of metastasis in lung. The anti-VEGF antibody may be potentially useful for clinical treatment of cancer and metastasis. Received: 2 January 1998 / Accepted: 17 March 1998     

Bradycardia-induced coronary angiogenesis is dependent on vascular endothelial growth factor.

A marked coronary angiogenesis is known to occur with chronic bradycardia. We tested the hypothesis that vascular endothelial growth factor (VEGF), an endothelial cell mitogen and a major regulator of angiogenesis, is upregulated in response to low heart rate and consequential increased stroke volume. Bradycardia was induced in rats by administering the bradycardic drug alinidine (3 mg/kg body weight) twice daily. Heart rate decreased by 32% for 20 to 40 minutes after injection and was chronically reduced by 10%, 14%, and 18.5% after 1, 2, and 3 weeks of treatment, respectively. Arterial pressure and cardiac output were unchanged. Left ventricular capillary length density (mm/mm(3)) increased gradually with alinidine administration; a 15% increase after 2 weeks and a 40% increase after 3 weeks of alinidine treatment were documented. Left ventricular weight, body weight, and their ratio were not significantly altered by alinidine treatment. After 1 week of treatment, before an increase in capillary length density, VEGF mRNA increased >2-fold and then declined to control levels after 3 weeks of treatment. VEGF protein was higher in alinidine-treated rats than in controls after 2 weeks and increased further after 3 weeks of treatment. Injection of VEGF-neutralizing antibodies over a 2-week period completely blocked alinidine-stimulated angiogenesis. In contrast, bFGF mRNA was not altered by alinidine treatment. These data suggest that VEGF plays a key role in the angiogenic response that occurs with chronic bradycardia. The mechanism underlying this VEGF-associated angiogenesis may be an increase in stretch due to enhanced diastolic filling.     

A permissive role for tumor necrosis factor in vascular endothelial growth factor-induced vascular permeability

Vascular endothelial growth factor (VEGF) induces both angiogenesis and an increase in vascular permeability, 2 processes that are considered to be important for both tumor growth and the delivery of drugs to the site of tumors. This study demonstrates that transmembrane expression of tumor necrosis factor (tmTNF) is up-regulated in the endothelium of a murine methylcholanthrene (meth A)-induced sarcoma in comparison to the adjacent normal dermal vasculature and is also present on cultivated human endothelial cells. It is further shown that tmTNF is required for VEGF-mediated endothelial hyperpermeability in vitro and in vivo. This permissive activity of TNF appears to be selective, because anti-TNF antibodies ablated the VEGF-induced permeability but not proliferation of cultivated human endothelial cells. Furthermore, tnf gene-deficient mice show no obvious defects in vascularization and develop normally but failed to respond to administration of VEGF with an increase in vascular permeability. Subsequent studies indicated that the tmTNF and VEGF signaling pathways converge at the level of a secondary messenger, the "stress-activated protein kinase-2" (SAPK-2)/p38: (1) up-regulated endothelial expression of tmTNF resulted in the continuous activation of SAPK-2/p38 in vitro, and (2) an inhibitor of SAPK-2/p38 activation abolished the vascular permeability activity of VEGF in vivo. In conclusion, the study's finding that continuous autocrine signaling by tmTNF sensitizes endothelial cells to respond to VEGF by increasing their vascular permeability provides new therapeutic concepts for manipulating vascular hyperpermeability.     

Catecholamine-induced vascular wall growth is dependent on generation of reactive oxygen species

Alpha1-adrenoceptor-dependent proliferation of vascular smooth muscle cells (VSMCs) is strongly augmented by vascular injury, and may contribute to intimal growth and lumen loss. Because reactive oxygen species (ROS) are increased by injury and have been implicated as second messengers in proliferation of VSMCs, we investigated the role of ROS in catecholamine-induced VSMC growth. Rat aortae were isolated 4 days after balloon injury, maintained in organ culture under circumferential wall tension, and exposed to agents for 48 hours. The antioxidants N-acetylcysteine (NAC, 10 mmol/L) and Tiron (5 mmol/L) and the flavin-inhibitor diphenylene iodonium (DPI, 20 micromol/L) abolished norepinephrine-induced increases in protein synthesis and DNA content in media. In aortic sections, norepinephrine augmented ROS production (dihydroethidium confocal microscopy), which was dose-dependently inhibited by NAC, Tiron, and DPI. In cultured VSMCs, phenylephrine caused time- and dose-dependent ROS generation (aconitase activity), had similar efficacy to thrombin (1 U/mL), and was eliminated by the superoxide dismutase (SOD) mimetic Mn-(III)-tetrakis-(4-benzoic-acid)-porphyrin-chloride (200 micromol/L) and Tiron. Phenylephrine-induced ROS production and increases in DNA and protein content were blocked by prazosin (0.3 micromol/L) and abolished in p47phox-/- cells. PEG-SOD (25 U/mL) had little effect, whereas PEG-catalase (50 U/mL) eliminated phenylephrine-induced proliferation in VSMCs. DPI (10 micromol/L) and apocynin (30 micromol/L) abolished phenylephrine-stimulated mitogenesis, whereas inhibitors of other intracellular ROS sources had not effect. Furthermore, PE increased p47phox expression (RT-PCR). These data demonstrate that the trophic effect of catecholamines on vascular wall cells is dependent on a ROS-sensitive step that we hypothesize consists of activation of the NAD(P)H-dependent vascular oxidase.     

GH sensitivity of GH-deficient adults is dependent on gender but not timing of onset

Background Females secrete 2–3‐fold greater amounts of GH compared with males despite maintaining similar IGF‐I levels. IGF‐I generation tests in healthy subjects suggest this discordancy results from relative resistance to GH in females. In GHD females the presumed relative insensitivity to GH is reflected by a lower basal IGF‐I and the need for higher GH maintenance doses during replacement. Adults with severe GHD of childhood‐onset (CO) have lower basal IGF‐I SDS and require higher GH maintenance doses compared with adult‐onset (AO) patients with GHD of equal severity. We hypothesised CO‐GHD adults to be less sensitive to GH than AO‐GHD patients. Methodology In a single site study we analysed the incremental change in IGF‐I (ΔIGF‐I) in 116 GHD adults following initiation of GH replacement. The data were corrected to provide ΔIGF‐I/mg GH because of slight variances in initial GH dose. Results Following GH replacement ΔIGF‐I was 230 ± 245 and 356 ± 278 ng/ml/mg GH in females and males, respectively (P = 0·01). In CO and AO patients ΔIGF‐I was 282 ± 206 and 294 ± 292 ng/ml/mg GH, respectively (P = 0·83). Further analysis after stratification by both gender and timing of onset of GHD showed ΔIGF‐I was 226 ± 164, 324 ± 228, 231 ± 268, and 373 ± 304 ng/ml/mg GH in the CO females, CO males, AO females, and AO males, respectively (AO males vs. AO females, P = 0·03; CO males vs. CO females, P = 0·17; AO males vs. CO males, P > 0·05; AO females vs. CO females, P > 0·05). Multiple linear regression with ΔIGF‐I as the dependent variable and age, gender, BMI, baseline IGF‐I level, and timing of onset as independent variables showed ΔIGF‐I to be dependent on gender alone (R = 0·28, P = 0·004). Age (P = 0·44), BMI (P = 0·54), baseline IGF‐I level (P = 0·63) and timing of onset (P = 0·61) had no effect on ΔIGF‐I. Conclusion We have shown gender to have a significant impact on GH sensitivity in GHD adults, which, at least in part, explains differences in maintenance dosages during replacement. None of the additional variables impacted significantly on GH sensitivity. The lower basal IGF‐I SDS and higher GH replacement requirement reported in CO compared with AO patients cannot be explained by differences in sensitivity to GH.     

GPR120 promotes metastasis but inhibits tumor growth in pancreatic ductal adenocarcinoma

ObjectivesG-protein-coupled receptor 120 (GPR120) is a long-chain unsaturated fatty acid receptor, which regulates glucose metabolism and lipid. To date, there are disputes on the roles of GPR120 in the pathogenesis of cancer. Besides, little is known about its roles in the pathogenesis of pancreatic ductal adenocarcinoma (PDAC). This study was designed to investigate the roles of GPR120 in the pathogenesis of PDAC.MethodsImmunohistochemical staining (IHC) was used for detecting the level of GPR120, epithelial-mesenchymal transformation (EMT) markers, Ki-67 and CD31 in ninety-one PDAC patients. Western blot, CCK8, flow cytometry and transwell assays were performed to determine proliferation, apoptosis, and motility in vitro. Subcutaneous tumor model was established to validate the roles of GPR120 in vivo.ResultsGPR120 was highly expressed in PDAC tissues, which was associated with free fatty acids (FFAs), lymph node metastasis (LNM), and poor prognosis. Moreover, GPR120 activation led to down-regulation of E-cadherin and up-regulation of Snail, Vimentin, N-cadherin, MMP2, MMP9, and CD31. Additionally, GPR120 decreased the expression of P-PI3K, P-AKT and CMYC and increased the level of P-JAK2, P-STAT3, Wnt5a, total β-catenin and β-catenin in nucleus.ConclusionsGPR120 promoted proliferation inhibition and apoptosis of PDAC, and contributed to PDAC metastasis via inducing EMT and angiogenesis. GPR120 served as a double-edged sword in the pathogenesis of PDAC.     

Angiopoietin-like 4 prevents metastasis through inhibition of vascular permeability and tumor cell motility and invasiveness

Angiopoietin-like 4 (ANGPTL4), a secreted protein of the angiopoietin-like family, is induced by hypoxia in both tumor and endothelial cells as well as in hypoxic perinecrotic areas of numerous cancers. Here, we investigated whether ANGPTL4 might affect tumor growth as well as metastasis. Metastatic 3LL cells were therefore xenografted into control mice and mice in which ANGPTL4 was expressed by using in vivo DNA electrotransfer. Whereas primary tumors grew at a similar rate in both groups, 3LL cells metastasized less efficiently to the lungs of mice that expressed ANGPTL4. Fewer 3LL emboli were observed in primary tumors, suggesting that intravasation of 3LL cells was inhibited by ANGPTL4. Furthermore, melanoma B16F0 cells injected into the retro-orbital sinus also metastasized less efficiently in mice expressing ANGPTL4. Although B16F0 cells were observed in lung vessels, they rarely invaded the parenchyma, suggesting that ANGPTL4 affects extravasation. In addition, recombinant B16F0 cells that overexpress ANGPTL4 were generated, showing a lower capacity for in vitro migration, invasion, and adhesion than control cells. Expression of ANGPTL4 induced reorganization of the actin cytoskeleton through inhibition of actin stress fiber formation and vinculin localization at focal contacts. Together, these results show that ANGPTL4, through its action on both vascular and tumor compartments, prevents the metastatic process by inhibiting vascular activity as well as tumor cell motility and invasiveness.     

Cointegrate formation by Tn5, but not transposition, is dependent on recA.

We have studied the effect of the recA-dependent homologous recombination system of Escherichia coli on both Tn5-mediated cointegrate formation and Tn5 transposition. We demonstrate here that, whereas transposition of Tn5 is independent of the recA gene product (as has been shown by other workers), Tn5-mediated cointegrate formation is strongly dependent on recA. The structures of both the simple transposition products and the cointegrates formed in a recA- background seem to be the same as those produced in a recA+ background. These results provide strong evidence that Tn5 does not transpose via an obligate cointegrate intermediate and suggest that the recA effect on cointegrate formation is exerted during the process of transposition.     

GPIb-dependent platelet activation is dependent on Src kinases but not MAP kinase or cGMP-dependent kinase

Glycoprotein Ib-IX-V (GPIb-IX-V) mediates platelet tethering to von Willebrand factor (VWF), recruiting platelets into the thrombus, and activates integrin alphaIIbbeta3 through a pathway that is dependent on Src kinases. In addition, recent reports indicate that activation of alphaIIbbeta3 by VWF is dependent on protein kinase G (PKG) and mitogen-activated protein (MAP) kinases. The present study compares the importance of these signaling pathways in the activation of alphaIIbbeta3 by GPIb-IX-V. In contrast to a recent report, VWF did not promote an increase in cyclic guanosine monophosphate (cGMP), while agents that elevate cGMP, such as the nitrous oxide (NO) donor glyco-SNAP-1 (N-(beta-D-glucopyranosyl)-N2-acetyl-S-nitroso-D,L-penicillaminamide) or the type 5 phosphosdiesterase inhibitor, sildenafil, inhibited rather than promoted activation of alphaIIbbeta3 by GPIb-IX-V and blocked aggregate formation on collagen at an intermediate rate of shear (800 s(-1)). Additionally, sildenafil increased blood flow in a rabbit model of thrombus formation in vivo. A novel inhibitor of the MAP kinase pathway, which is active in plasma, PD184161, had no effect on aggregate formation on collagen under flow conditions, whereas a novel inhibitor of Src kinases, which is also active in plasma, PD173952, blocked this response. These results demonstrate a critical role for Src kinases but not MAP kinases in VWF-dependent platelet activation and demonstrate an inhibitory role for cGMP-elevating agents in regulating this process.     

Pneumothorax-associated pleural eosinophilia in mice is interleukin-5 but not interleukin-13 dependent

STUDY OBJECTIVES: To establish a murine model of pneumothorax-associated pleural eosinophilia and to examine the role of interleukin (IL)-5 and IL-13 in the pathogenesis of this reaction. DESIGN: An animal study. INTERVENTIONS: One hundred thirty-seven C57/Bl-6 mice were used in this study. Wild-type animals were injected intrapleurally with 0.4 mL of air and were killed at different time points (30 min to 7 days) after the injection. IL-5 knockout and IL-13 knockout animals were killed 24 h and 48 h after the injection. Pleural inflammation was assessed by pleural lavage (PL). MEASUREMENTS AND RESULTS: PL cells were significantly increased following the induction of pneumothorax. The peak number of neutrophils, observed at 12 h, was 900 times higher than the control. The peak number of eosinophils, observed at 48 h, was 700 times higher than the control. Lymphocytes and mononuclear cells increased threefold and fourfold, respectively. IL-5 knockout mice had significantly less PL eosinophils than that the wild-type or the IL-13 knockout mice at 24 h (150 +/- 46/microL, 903 +/- 244/microL, and 912 +/- 168/microL, respectively; p = 0.013) and 48 h (181 +/- 45/microL, 1,587 +/- 212/microL, and 1,379 +/- 364/microL, respectively; p = 0.003). CONCLUSION: Pneumothorax induces an inflammatory reaction of the mouse pleura, mainly characterized by increased neutrophils and eosinophils. IL-5 but not IL-13 is required for pneumothorax-associated pleural eosinophilia.     

Mid-luteal angiogenesis and function in the primate is dependent on vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is essential for the angiogenesis required for the formation of the corpus luteum; however, its role in ongoing luteal angiogenesis and in the maintenance of the established vascular network is unknown. The aim of this study was to determine whether VEGF inhibition could intervene in ongoing luteal angiogenesis using immunoneutralisation of VEGF starting in the mid-luteal phase. In addition, the effects on endothelial cell survival and the recruitment of periendothelial support cells were examined. Treatment with a monoclonal antibody to VEGF, or mouse gamma globulin for control animals, commenced on day 7 after ovulation and continued for 3 days. Bromodeoxyuridine (BrdU), used to label proliferating cells to obtain a proliferation index, was administered one hour before collecting ovaries from control and treated animals. Ovarian sections were stained using antibodies to BrdU, the endothelial cell marker, CD31, the pericyte marker, alpha-smooth muscle actin, and 3' end DNA fragments as a marker for apoptosis. VEGF immunoneutralisation significantly suppressed endothelial cell proliferation and the area occupied by endothelial cells while increasing pericyte coverage and the incidence of endothelial cell apoptosis. Luteal function was markedly compromised by anti-VEGF treatment as judged by a 50% reduction in plasma progesterone concentration. It is concluded that ongoing angiogenesis in the mid-luteal phase is primarily driven by VEGF, and that a proportion of endothelial cells of the mid-luteal phase vasculature are dependent on VEGF support.     

Angiogenesis mediated by metabolites is dependent on vascular endothelial growth factor (VEGF)

Metabolites released from hypoxic tissues have recently been reported to be angiogenic, although it remains to be clarified if they have a role independent of the upregulation of hypoxia-inducible genes such as vascular endothelial growth factor (VEGF). In an attempt to conclusively evaluate their role, the metabolites lactate, pyruvate, malate and adenosine were tested in a two-dimensional in vitro angiogenesis assay which consists of human umbilical vein endothelial cells (HUVECs) co-cultured with fibroblasts of dermal origin. In addition, ethanol was tested. Metabolism of ethanol leads to increased levels of lactate and malate, which may explain its recently reported angiogenic properties. Lactate, malate, adenosine and ethanol produced a significant angiogenic response, although this was only observed at certain concentrations. However this angiogenic response was abolished when repeated in the presence of neutralising anti-VEGF antibodies. The results of this study therefore indicate that the angiogenic potential of metabolites is dependent upon increased expression of VEGF.     

Apocynin is not an inhibitor of vascular NADPH oxidases but an antioxidant

A large body of literature suggest that vascular reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases are important sources of reactive oxygen species. Many studies, however, relied on data obtained with the inhibitor apocynin (4'-hydroxy-3'methoxyacetophenone). Because the mode of action of apocynin, however, is elusive, we determined its mechanism of inhibition on vascular NADPH oxidases. In HEK293 cells overexpressing NADPH oxidase isoforms (Nox1, Nox2, or Nox4), apocynin failed to inhibit superoxide anion generation detected by lucigenin chemiluminescence. In contrast, apocynin interfered with the detection of reactive oxygen species in assay systems selective for hydrogen peroxide or hydroxyl radicals. Importantly, apocynin interfered directly with the detection of peroxides but not superoxide, if generated by xanthine/xanthine oxidase or nonenzymatic systems. In leukocytes, apocynin is a prodrug that is activated by myeloperoxidase, a process that results in the formation of apocynin dimers. Endothelial cells and smooth muscle cells failed to form these dimers and, therefore, are not able to activate apocynin. Dimer formation was, however, observed in Nox-overexpressing HEK293 cells when myeloperoxidase was supplemented. As a consequence, apocynin should only inhibit NADPH oxidase in leukocytes, whereas in vascular cells, the compound could act as an antioxidant. Indeed, in vascular smooth muscle cells, the activation of the redox-sensitive kinases p38-mitogen-activate protein kinase, Akt, and extracellular signal-regulated kinase 1/2 by hydrogen peroxide and by the intracellular radical generator menadione was prevented in the presence of apocynin. These observations indicate that apocynin predominantly acts as an antioxidant in endothelial cells and vascular smooth muscle cells and should not be used as an NADPH oxidase inhibitor in vascular systems.     

Circulating vascular endothelial growth factor (VEGF) is a possible tumor marker for metastasis in human hepatocellular carcinoma

Vascular endothelial growth factor (VEGF) is closely related to angiogenesis in various human cancers. However, little is known of its circulating levels in hepatocellular carcinoma (HCC). We examined circulating VEGF levels in chronic liver disease to assess their clinical significance. Plasma VEGF concentrations were determined, by enzyme immunoassay, in patients with chronic hepatitis (CH; n = 36), liver cirrhosis (LC; n = 77), and HCC (n = 86) for a cross-sectional study. Plasma VEGF levels in healthy controls (n = 20) and CH, LC, and HCC patients were 17.7 ± 5.4 (mean ± SD), 30.6 ± 22.8, 34.4 ± 27.0, and 51.1 ± 71.9 pg/ml, respectively. The levels were significantly elevated in the HCC group, compared with the control, CH, and LC groups. Plasma VEGF levels in stage I, II, III, IVA, and IVB HCC patients were 27.6 ± 16.1, 26.5 ± 13.7, 35.8 ± 15.3, 45.4 ± 39.4, and 103.1 ± 123.2 pg/ml, respectively. The stage IVB patients with remote metastasis showed significantly marked elevation compared with the patients at the other stages. Platelet numbers were weakly correlated with plasma VEGF levels in the HCC group. Plasma VEGF level was highly elevated in patients with HCC, particularly those with metastatic disease. We consider that plasma VEGF is a possible tumor marker for metastasis of HCC. Circulating VEGF may be derived mainly from the large burden of tumor cells, and partly from platelets activated by the vascular invasion of HCC cells. (Received June 30, 1997; accepted Oct. 30, 1997)     

Apomorphine-induced growth hormone response is attenuated by ethanol but not dextromethorphan

BACKGROUND: Misuse of alcohol drinking is a major health problem. Alcohol decreases spontaneous growth hormone (GH) secretion, but the mechanism is unclear. The aim of this study was to test whether administration of alcohol (study 1) or a N-methyl d-aspartate (NMDA) receptor antagonist (study 2) attenuates the GH response to pharmacological dopaminergic stimulation. METHODS: The 2-session repeated measures design was conducted at the endocrine laboratory at the Department of Psychiatry at the Free University Berlin. Twenty healthy Caucasian males aged 35+/-10 years without a history of alcohol use disorders were tested using the Apomorphine (APO) challenge test. In study 1, we injected APO (0.01 mg/kg s.c.) 1 hour after oral administration of 1 g/kg ethanol and placebo, respectively. In study 2, the APO challenge was conducted after 0.3 mg/kg dextromethorphan (DXM) and placebo. The main outcome measures were the peak serum GH concentration and area under the time/concentration curve up to 120 minutes after APO. The effects of ethanol and DXM were tested using the Wilcoxon signed-rank tests. RESULTS: Compared with placebo, alcohol significantly decreased the APO-induced GH release (mean and SEM peak GH concentration 19.9+/-3.2 vs 6.2+/-1.9 ng/mL, p=0.002). Dextromethorphan did not change APO-induced GH response (22.5+/-5.4 vs 21.0+/-5.8 ng/mL, p=0.105). CONCLUSION: A single intermediate alcohol dose markedly reduces GH response to dopaminergic stimulation. Although alcohol is thought to stimulate dopaminergic function in certain pathways, but not necessarily in the hypothalamus, our results are in line with the alcohol effect on baseline GH secretion. Growth hormone suppression appears not to be mediated by ethanol's NMDA-antagonistic properties.     

Nutritional regulation of IGF-II, but not IGF-I, is age dependent in sheep

In post-natal animals, plasma concentrations of IGF-I are tightly regulated by nutritional status. The current study reports that plasma levels of IGF-II in sheep are also regulated by nutrition, but whether plasma IGF-II is increased, decreased or remains the same, depends on the age of the animal. Ewe lambs, ranging in age from 2 days to 2 years, were fed or fasted for lengths of time between 24 and 72 h. Blood samples were taken at intervals of 24 h throughout the treatment period and immediately before slaughter. Plasma concentrations of IGF-I increased with advancing age in fed animals (P<0.001) and were reduced by fasting in all age groups (P<0.001). Plasma concentrations of IGF-II also increased as animals matured (P<0.001), but did not show an overall effect of the fasting treatment. An interaction between age and nutrition (P<0.001) resulted from a decrease in plasma IGF-II in response to fasting in neonatal animals (P<0.01) and, conversely, increased levels of plasma IGF-II in fasted mature animals (P<0.01 or P<0.001). Fasted sheep of peripubertal age showed no change in plasma levels of IGF-II. The nutritional sensitivity of serum IGF-binding proteins (BPs) also changed with age. The 29 kDa BP, which we presume to be BP1, was elevated by fasting in young animals and reduced slightly in older animals. BP2 was increased to a similar magnitude by fasting at all ages. BP3 was depressed by fasting in young animals and showed little change in adults. In contrast, a 24 kDa BP, which is probably BP4, showed little change in young animals and was reduced substantially in older sheep. In conclusion, the response of plasma IGF-II to fasting suggests that this peptide has functions in mediating nutritional stress which depend on the age of the animal, and also that the role of IGF-II may differ from that of IGF-I in adults.