Interaction Of Human Growth Hormone Research Articles

Simultaneous electrochemical investigation and detection of two glucocorticoids; interactions with human growth hormone, somatropin

In the present work, the simultaneous determination of dexamethasone (DXM) and hydrocortisone (HYD) is described by the use of a nano-porous glassy carbon electrode (GCE), prepared via an electrochemical treatment. Nano-porous/GCE provided the porosity which was increased the sensitivity of the surface of electrode to monitor the drugs. Differential pulse voltammetry (DPV) was used for the determination of DXM and HYD simultaneously at the surface of the electrode. Under the optimum pH 2 (0.1 M, phosphate buffer solution), it is found that the calibration plots for DXM and HYD are linear in the concentration ranges 0.02–22 and 0.1–42 µM with detection limits of 5 and 30 nM for DXM and HYD, respectively. Also, the interaction of human growth hormone (somatropin) with DXM and HYD has been studied by electrochemical and UV–Vis spectroscopy techniques. The binding of DXM and HYD to human growth hormone was also modeled by molecular docking methods. The glucocorticoids could inhibit the application of the human growth hormone.

Growth hormone receptor antagonist in the treatment of acromegaly

Exploration of construction, function and interaction of human growth hormone and growth hormone receptor in details resulted in the innovation of the new growth hormone receptor antagonist, pegvisomant. Pegvisomant with different mechanism of action extended the tools of medical management of acromegaly. Importance of the novel treatment modality is high. In one hand the necessity of the strict control of growth hormone/insulin-like growth factor-I axis has been proven regarding the mortality of the disease. On the other hand, despite the use of all current modes of treatment (surgery, radiotherapy, dopamine agonists, somatostatin analogs), a significant cohort of patients with acromegaly remains inadequately controlled. Pegvisomant has been registered in 2004. Since 2006, it has been used in Hungary for the treatment of acromegaly in patients who have had an inadequate response to surgery and/or radiation therapy and/or other medical therapies, or for whom these therapies are not appropriate. Clinical use of pegvisomant in the treatment of acromegaly is effective, well tolerated, and safe, based on international Acrostudy database. In order to improve the efficacy of therapy clinical trials started with pegvisomant and somatostatin analog combination treatment. Evidence of several further effects of the growth hormone/insulin-like growth factor-I axis suggests other potential uses of growth hormone receptor antagonists.

Thermodynamic Study of the Binding of Mercury Ion to Human Growth Hormone at Different Temperatures

The interaction of human growth hormone (hGH) with the divalent mercury ion was studied by isothermal titration calorimetry at two temperatures of 27 °C and 37 °C in aqueous solutions. We found that there is a set of two identical and non-interacting binding sites for Hg2+ ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 4.2 mmol⋅L−1 and −14.8 kJ⋅mol−1 at 27 °C and 5.1 mmol⋅L−1 and −14.2 kJ⋅mol−1 at 37 °C, respectively. The results obtained indicate that the stability of the protein increases due to the binding of mercury ions using the extended solvation theory.

Application of a simple calorimetric data analysis on the binding study of calcium ions by human growth hormone

A simple graphical linear method was introduced for isothermal titration calorimetric data analysis in the protein-ligand interaction. The number of binding sites, the dissociation binding constant and the molar enthalpy of binding site can be obtained by using this new isothermal titration calorimetric data analysis method. The method was applied to the study of the interaction of human growth hormone (hGH) with divalent calcium ion at 27°C in NaCl solution, 50 mM. hGH has a set of three identical and independent binding sites for Ca 2+ . The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 52 μMand -17.4, respectively. Results obtained by this new calorimetric data analysis are in good agreement with results obtained using our previous method.

The Thrombin Epitope Recognizing Thrombomodulin Is a Highly Cooperative Hot Spot in Exosite I

The functional epitope of thrombin recognizing thrombomodulin was mapped using Ala-scanning mutagenesis of 54 residues located around the active site, the Na(+) binding loop, the 186-loop, the autolysis loop, exosite I, and exosite II. The epitope for thrombomodulin binding is shaped as a hot spot in exosite I, centered around the buried ion quartet formed by Arg(67), Lys(70), Glu(77), and Glu(80), and capped by the hydrophobic residues Tyr(76) and Ile(82). The hot spot is a much smaller subset of the structural epitope for thrombomodulin binding recently documented by x-ray crystallography. Interestingly, the contribution of each residue of the epitope to the binding free energy shows no correlation with the change in its accessible surface area upon formation of the thrombin-thrombomodulin complex. Furthermore, residues of the epitope are strongly coupled in the recognition of thrombomodulin, as seen for the interaction of human growth hormone and insulin with their receptors. Finally, the Ala substitution of two negatively charged residues in exosite II, Asp(100) and Asp(178), is found unexpectedly to significantly increase thrombomodulin binding.

Interaction of Human Growth Hormone and Gonadotrophins on the Function of Rat Ovaries

Hypophysectomized and normal female rats were used for studying the interaction of human growth hormone and gonadotrophins in stimulating the rat ovary. Groups of rats were injected with increasing doses of gonadotrophins (Pergonal or Metrodin) in addition to human growth hormone (Norditropin) or placebo. In the test for follicle stimulating hormone activity the weight of the ovaries was recorded. In the hypophysectomized rats Norditropin and Pergonal or Metrodin had a synergistic stimulating effect on the ovary, resulting in a greater number and a larger follicle size. Norditropin had a slight stimulatory effect of its own. In the ovarian ascorbic acid depletion test for luteinising hormone activity Norditropin had a significant effect of its own. In combination with Pergonal an additive effect was seen. The effect of Norditropin was observed in hypophysectomized rats only.

Irreversibility of the interaction of human growth hormone with its receptor and analysis of irreversible reactions in radioreceptor assays—Theoretical considerations

Kinetic studies of the binding and dissociation of [125I]-human growth hormone to rabbit liver and mammary gland membrane receptors have showed that the binding of [125I]-human growth hormone was largely irreversible to liver membrane receptors and completely to the solubilised mammary gland receptor. As Scatchard analysis assumes complete reversibility of the hormone-receptor interaction the validity of estimates of affinity and capacity of receptors derived by this analysis may be questionable.

In vivo interaction of human growth hormone (HGH) with subcellular structures of rat liver

The interaction of circulating HGH with subcellular structures of female rat liver was studied in the intact animal. Various subcellular fractions including plasma membranes (Biochim. Biophys. Acta 154 : 540, 1968) and Golgi fractions (J. Cell. Biol. 59 : 45, 1973) were prepared from liver homogenates at different time intervals after a single injection of 125I-HGH into a peripheral vein. Labeling of plasma membranes occurred within the first minutes following injection, whereas labeling of Golgi fractions was delayed and reached a maximum by 15 minutes. Labeling of both subcellular structures was inhibited by excess (500 μg) native HGH but was unaffected by insulin. At all times studied virtually no radioactivity was found in the nuclear and mitochondrial-lysozomal fractions. The 125I-HGH eluted from the plasma membranes and from Golgi fractions appeared intact as tested by TCA precipitation and rebinding to rat liver membrane. The results suggest that, following binding to the surface of liver cells, HGH is translocated into Golgi elements under a biologically active form.

Interaction of Human Growth Hormone With Isolated Rat Liver Cells

The interaction of 125I-labeled human growth hormone (hGH) with isolated rat liver cells is a specific, time dependent and saturable process. In male rats, one cell binds a maximum of 2000 hormone molecules; the dissociation constant of the cell-hGH interaction is about 3 X 10(-10)M. Liver cells of female rats bind 5 to 10 times more hGH than do those of male rats at equivalent hormone concentrations. Binding of 125I-labeled hGH to liver cells is readily inhibited by native hGH; 50% inhibition occurs at about 2 X 10(-9)M hGH irrespective of sex. In male rats, bovine growth hormone (bGH) is almost as potent as hGH in inhibiting 125I-labeled hGH binding; no displacement occurs with ovine prolactin (oPRL) except at very high (greater than 10(-6)M) concentrations. In female rats, bGH competes less effectively, and oPRL, more effectively, than they do in males; in addition, oPRL demonstrates a higher apparent affinity for the hGH binding sites (4 X 10(-9)M) than does bGH (1 X 10(-8M). These findings suggest that in female rats hGH, unlike bGH, interacts with additional, "lactogenic" binding sites that are distinct from the "growth hormone" binding sites. The 125I-labeled hGH eluted from liver cells as well as that which remains in the incubation medium retains full biological activity, as judged on its ability to bind specifically to liver membranes. Treatment of liver cells by phospholipase A causes a 5-fold increase in cell binding capacity. Liver cells bind about the same amount of hGH as do crude particulate fractions from these cells; this suggests that in the intact cell, binding occurs at relatively accessible sites, presumably localized in the plasma membrane.

BINDING STUDIES OF GROWTH HORMDNE TO RAT LIVER CELLS

The interaction of human growth hormone (HGH) with isolated liver cells from normal rats has been studied. Cells prepared with the method described by Berry and Friend were incubated at room temperature with 125I-labeled HGH. Free and cell-bound hormone were separated by filtration or centrifugation. The binding of 125I-HGH to liver cells is a specific, time dependent, saturable and reversible process. At a hormone concentration of 5 × 10−11M, equilibrium of binding is achieved in 120 minutes. The bound labeled HGH is rapidly dissociated by addition of an excess of unlabeled hormone. The specific binding of 125I-HGH is saturable at a hormone concentration of 6 × 10−10M. 1500 molecules of HGH are specifically bound per cell. Native HGH inhibits binding of 125I-HGH to cells; half maximal inhibition occurs at 4 × 10−9M. No significant inactivation or degradation of 125I-HGH or of the specific receptors occurs. Preliminary data indicate that those receptor sites are biologically meaningful.

Binding of 125I-Human Growth Hormone to Specific Receptors in Human Cultured Lymphocytes: CHARACTERIZATION OF THE INTERACTION AND A SENSITIVE RADIORECEPTOR ASSAY

Abstract The interaction of human growth hormone with human lymphocytes from an established culture (IM-9) was studied using 125I-human growth hormone. The binding of 125I-human growth hormone was rapid; with human growth hormone at 0.1 nm a steady state was observed in 90 min at 30°. Bound labeled human growth hormone was dissociated rapidly by addition of excess unlabeled human growth hormone. Binding of 125I-human growth hormone to cultured lymphocytes was relatively insensitive to alterations in the pH and in the concentrations of Ca2+, Mg2+, or EDTA. At 30° there was very little degradation of labeled human growth hormone or of the specific receptor sites. Tryptic digestion destroyed the capacity of cells to bind human growth hormone. The IM-9 cells bound all human growth hormone preparations but not unrelated hormones or nonprimate growth hormones. The binding of 125I-human growth hormone was inhibited 10 to 14% with 1 to 2 ng per ml of unlabeled human growth hormone and 50% with 30 to 40 ng per ml, well within the range of hormone concentrations in vivo. Analysis of steady state data revealed a single order of binding sites with an affinity constant of 1.3 x 109 m-1 and about 4000 binding sites per cell. Numerous human growth hormone preparations were assayed by use of this receptor system as well as by immunoassay and by bioassay in vivo. The potencies of the human growth hormone preparations determined by the radioreceptor assay correlated more closely with the bioassay than with the radioimmunoassay.

Interaction of human growth hormone and human erythrocyte membranes studies by intrinsic fluorescence.

The intrinsic fluorescence of human erythrocyte membranes excited by unpolarized and polarized light has been studied with and without the addition of human growth hormone. The peak emission intensity of the membranes appeared at 332 nm, with a distinct shoulder at about 303 nm. Excitation spectra contained two peaks, at 282 and 225 nm. Fluorescence polarization was maximal (about 0.4) near 295 nm and decreased to approximately 0.18 near 225 nm. In the presence of 1 x 10(-15) M human growth hormone, or 70 molecules per membrane (1.45 x 10(-6) cm(2)), there was about a 20% decrease in peak membrane fluorescence. This occurred maximally with excitation at 282 and 225 nm, with little difference with excitation at 295 nm. Human growth hormone also decreased the fluorescence polarization from 0.34 to 0.25. The growth hormone effect was optimal at 37 degrees C and pH 7.4. No effect was noted at pH 6.0 or 8.0. Bovine growth hormone or bovine serum albumin was without effect. A biologically active fragment from a tryptic digest of bovine growth hormone produced effects on membrane fluorescence similar to human growth hormone. The data are consistent with the proposition that human growth hormone, by some cooperative mechanism, produces a conformational change in the membrane proteins with associated depolarization of fluorescence.

Interaction of human growth hormone and human erythrocyte membranes as demonstrated by

Human growth hormone in physiological concentrations induced a change in the ellipticity of human erythrocyte membranes at 222 mμ from −11,800 deg cm2/decimole to about −8,800 deg cm2/decimole. Bovine growth hormone, bovine serum albumin, bovine insulin or cortisol were without effect. This effect was demonstrable in the presence of phosphate buffer but not in distilled water. Erythrocyte membranes modified the near ultraviolet spectrum of human growth hormone. None of the effects observed could be accounted for by distortions due to light scattering or absorption flattening.