Degradation of IGF-I in the adult rat gastrointestinal tract is limited by a specific antiserum or the dietary protein casein

1995 ◽  
Vol 146 (2) ◽  
pp. 215-225 ◽  
Author(s):  
C J Xian ◽  
C A Shoubridge ◽  
L C Read
Keyword(s):  
Receptor Binding ◽  
Dietary Protein ◽  
Half Life ◽  
Structural Integrity ◽  
Binding Activity ◽  
Adult Rats ◽  
Adult Rat ◽  
Igf I

Abstract To investigate the potential of IGF-I peptides as therapeutics in the gut, the survival profiles of a bolus of 125I-labelled IGF-I (8·6 ng) in vivo in various ligated gut segments of fasted adult rats have been examined. The intactness of IGF-I tracer in the flushed luminal contents was estimated by trichloroacetic acid precipitation, antibody and receptor binding assays. It was found that IGF-I was degraded very rapidly in duodenum and ileum segments with a half-life (t1/2) of 2 min by all three methods. IGF-I was slightly more stable in the stomach (t1/2=8, 5 and 2·5 min by the above three methods), and considerably more stable in the colon (t1/2=38, 33 and 16 min as judged by the three methods). Rates of degradation in gut flushings in vitro were similar to the in vivo rates except for the colon, where IGF-I was proteolysed more rapidly in vivo. As a means of developing gut-stable and active forms of IGF-I, several approaches were examined for their effectiveness in prolonging IGF-I survival in the upper gut. It was found that the extension peptide on the analogue, LR3IGF-I did not protect IGF-I, nor did association with IGF-binding protein-3. However, an IGF-I antiserum was effective in prolonging IGF-I half-life in duodenum fluid by 28-fold. Charge interaction between IGF-I and heparin could also protect IGF-I in the stomach but not in duodenum flushings. Furthermore, casein (a non-specific dietary protein) and to a lesser extent, BSA and lactoferrin, were effective in preserving IGF-I structural integrity and receptor binding activity in both stomach and duodenum fluids. It can be concluded that IGF-I cannot be expected to retain bioactivity if delivered orally because of rapid proteolysis in the upper gut, but the use of IGF antibodies and casein could represent useful approaches for IGF-I protection in oral formulae. Journal of Endocrinology (1995) 146, 215–225

Effects of hypophysectomy and subsequent FSH and testosterone treatment on inhibin production by adult rat testes

1985 ◽  
Vol 105 (1) ◽  
pp. 1-6 ◽  
Author(s):  
C. L. Au ◽  
D. M. Robertson ◽  
D. M. de Kretser
Keyword(s):  
Seminiferous Tubule ◽  
Hormonal Control ◽  
Human Chorionic Gonadotrophin ◽  
Experimental Conditions ◽  
Adult Rats ◽  
Adult Rat ◽  
Fluid Production ◽  
Tubule Fluid

ABSTRACT The hormonal control of inhibin production by adult rat testes was investigated using an in-vitro inhibin bioassay validated for the measurement of inhibin activity in charcoal-treated rat testicular extracts. The effect of hypophysectomy examined at 16 h, 3, 7 and 42 days after surgery showed a decrease in testicular inhibin content and seminiferous tubule fluid production by 7 days and a decrease in inhibin production by 42 days. Serum FSH and LH were suppressed 3 days after surgery. In 30-day chronically hypophysectomized adult rats treated for 3 days with twice daily s.c. injections of (a) human FSH (hFSH, 22 i.u./rat per day), (b) testosterone (5 mg/rat per day), (c) hFSH + testosterone (same doses as a and b), or (d) human chorionic gonadotrophin (hCG, 12 i.u./rat per day), hFSH or hFSH and testosterone stimulated an increase in testicular inhibin content but not in inhibin production or tubule fluid production. Testosterone and hCG had no effect on these parameters. It is concluded that in vivo, FSH alone stimulates an increase in testicular inhibin content. The failure to observe an increase in inhibin production in vivo is attributed to the suppression of seminiferous tubule fluid production under the same experimental conditions. J. Endocr. (1985) 105, 1–6

Insulin-like growth factor I receptors in adult rat liver: characterization and in vivo regulation

1990 ◽  
Vol 258 (2) ◽  
pp. E329-E337 ◽  
Author(s):  
N. Venkatesan ◽  
M. B. Davidson
Keyword(s):  
Growth Factor ◽  
Rat Liver ◽  
Structural Changes ◽  
Electrophoretic Analysis ◽  
Binding Activity ◽  
Female Rats ◽  
Insulin Like Growth Factor ◽  
Adult Rat ◽  
Igf I

Although the presence of significant amounts of insulin-like growth factor (IGF)-I receptors in fetal tissues is well documented, adult liver has been reported to contain little or no IGF-I binding activity. In the present investigation, substantial amounts of specific IGF-I receptors were detected in crude membrane fractions and in partially purified receptor preparations of female adult rat liver. Insulin was 100 times less potent than IGF-I in competing for 125I-IGF-I binding. IGF-I binding activity was much less than that of insulin binding in both the microsomal fraction and partially purified receptor preparations. Affinity cross-linking of 125I-IGF-I to purified receptors and microsomal fractions followed by electrophoretic analysis under nonreducing conditions revealed labeling of proteins with relative molecular weight (Mr) of 350,000 and 210,000-220,000, corresponding to the molecular mass of the intact tetramer and alpha-beta dimers, respectively. Under reducing conditions, the labeling of proteins with Mr of 130,000 and 260,000, corresponding to the alpha-subunit of IGF-I receptor and its dimer, respectively, was observed. Treatment of microsomes as well as partially purified receptors with 0.5-1 mM dithiothreitol resulted in decreased IGF-I binding, and this correlated with structural changes in the receptor as detected by affinity labeling and electrophoretic analysis. Hepatic IGF-I binding activity was significantly diminished in female rats exposed to chronic growth hormone excess, suggesting down-regulation of IGF-I receptors by the enhanced circulating levels of IGF-I in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Postovulatory steroidogenesis after PMS-induced ovulation in immature female rats

1981 ◽  
Vol 241 (3) ◽  
pp. E221-E225 ◽  
Author(s):  
K. Taya ◽  
G. S. Greenwald
Keyword(s):  
Serum Levels ◽  
Female Rats ◽  
Corpora Lutea ◽  
Adult Rats ◽  
Rat Serum ◽  
Follicular Maturation ◽  
Adult Rat ◽  
Serum Lh

Thirty-day-old rats given a single subcutaneous injection of 5 IU pregnant mare serum gonadotropin (PMS) at 0900 h ovulated on the morning of day 33 (= estrus). However, the second ovulation did not occur until 9.4 days later. To determine the mechanism responsible for the delay in the second ovulation, in vivo and in vitro determinations of steroid and peptide hormones were compared between PMS-primed immature rats and adult cyclic rats. In PMS-primed rats, the corpora lutea (CL) produced progesterone for 2 days longer (until day 36) than the CL of the adult rat. Serum levels of 20 alpha-dihydroprogesterone, testosterone, and estradiol in PMS-primed rats were significantly lower than the corresponding values in adult rats. Serum LH was consistently lower in the PMS-primed rats. An increase in serum FSH occurred on days 36–37, which may be responsible for maturation of the follicles destined to ovulate at the second ovulation. On day 37, the nonluteal ovary of the PMS-primed rats also began to produce in vitro appreciable amounts of testosterone and estradiol. These findings suggest that the greater levels of prolactin and/or low levels of luteinizing hormone during estrus in PMS-primed rats may be responsible for the prolonged secretion of progesterone by the CL. This in turn inhibits follicular maturation, indirectly by lowering serum LH, which is reflected in reduced ability of the follicles in vitro to produce testosterone and estradiol until the CL regress.

Local Circuit Properties Underlying Cortical Reorganization

2002 ◽  
Vol 88 (3) ◽  
pp. 1288-1301 ◽  
Author(s):  
Peter W. Hickmott ◽  
Michael M. Merzenich
Keyword(s):  
Cortical Reorganization ◽  
The Novel ◽  
Adult Rats ◽  
Postsynaptic Potentials ◽  
Local Circuit ◽  
Adult Rat ◽  
The Times ◽  
Stimulation Of

Peripheral denervation has been shown to cause reorganization of the deafferented somatotopic region in primary somatosensory cortex (S1). However, the basic mechanisms that underlie reorganization are not well understood. In the experiments described in this paper, a novel in vivo/in vitro preparation of adult rat S1 was used to determine changes in local circuit properties associated with the denervation-induced plasticity of the cortical representation in rat S1. In the present studies, deafferentation of rat S1 was induced by cutting the radial and median nerves in the forelimb of adult rats, resulting in a rapid shift of the location of the forepaw/lower jaw border; the amount of the shift increased over the times assayed, through 28 days after denervation. The locations of both borders (i.e., original and reorganized) were marked with vital dyes, and slices from the marked region were used for whole-cell recording. Responses were evoked using electrical stimulation of supragranular S1 and recorded in supragranular neurons close to either the original or reorganized border. For each neuron, postsynaptic potentials (PSPs) were evoked by stimulation of fibers that crossed the border site (CB stim) and by equivalent stimulation that did not cross (NCB stim). Monosynaptic inhibitory postsynaptic potentials (IPSPs) were also examined after blocking excitatory transmission with 15 μM CNQX plus 100 μMdl-APV. The amplitudes of PSPs and IPSPs were compared between CB and NCB stimulation to quantify effects of the border sites on excitation and inhibition. Previous results using this preparation in the normal (i.e., without induced plasticity) rat S1 demonstrated that at a normal border both PSPs and IPSPs were smaller when evoked with CB stimulation than with NCB stimulation. For most durations of denervation, a similar bias (i.e., smaller responses with CB stimulation) for PSPs and IPSPs was observed at the site of the novel reorganized border, while no such bias was observed at the suppressed original border site. Thus changes in local circuit properties (excitation and inhibition) can reflect larger-scale changes in cortical organization. However, specific dissociations between these local circuit properties and the presence of the novel border at certain durations of denervation were also observed, suggesting that there are several intracortical processes contributing to cortical reorganization over time and that excitation and inhibition may contribute differentially to them.

scholarly journals Effect of thyroxine administration on the IGF/IGF binding protein system in neonatal and adult thyroidectomized rats

2001 ◽  
Vol 169 (1) ◽  
pp. 111-122 ◽  
Author(s):  
S Ramos ◽  
L Goya ◽  
C Alvarez ◽  
MA Martin ◽  
AM Pascual-Leone
Keyword(s):  
Body Weight ◽  
Mrna Expression ◽  
Plasma Insulin ◽  
Binding Protein ◽  
Adult Rats ◽  
Igf I ◽  
Igf Binding ◽  
Igf Binding Protein

The effects of different doses of thyroxine (T(4)) delivered by injection or s.c. pellet implantation on alterations of the IGF/IGF binding protein (IGFBP) system were studied in neonatal and adult thyroidectomized (Tx) rats. Body weight, blood glucose, plasma insulin, TSH and GH and pituitary GH content, as well as serum IGF-I, IGF-II, IGFBP-1, -2 and -3 and their liver mRNA expression were assayed. Pellet implantation with the smaller dose of T(4) (1.5 microg/100 g body weight (b.w.) per day) in Tx neonatal rats decreased serum IGF-I, -II and the 30 kDa complex of IGFBPs (IGFBP-1 and -2), and increased serum IGFBP-3. Only the larger dose of T(4) (3 microg/100 g b.w. per day) recovered liver mRNA expression of IGF-I and ensured euthyroid status as shown by the normalized levels of plasma TSH. The rapid increase of body weight and serum GH after T(4) administration indicated a high sensitivity to T(4) during the neonatal period. Serum and liver mRNA expression of IGFs and plasma insulin and GH recovered in adult Tx rats after pellet implantation of 1.75 microg/100 g b.w. per day throughout 10 days. The continuous replacement of T(4) by pellet seems to be the most suitable method for thyroid rehabilitation. A very good correlation was found between insulin and IGF-II in Tx neonates treated with T(4) but not between insulin and IGF-I in Tx adults. IGFBP-2 seems to be up-regulated by T(4) deprivation in neonatal and adult rats. Finally, a good correlation as well as a partial correlation were found between IGFs and thyroid hormones in both neonatal and adult Tx populations, suggesting a direct effect in vivo of T(4) on the hepatic secretion of IGFs, as previously suggested in vitro.

Abstract 15601: On the Mechanisms of Accelerated Calcification of Bioprosthetic Heart Valve Biomaterials in Juvenile Animal Models

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Yingfei Xue ◽  
Alexander Kossar ◽  
Gaetano THIENE ◽  
Robert LEVY ◽  
Giovanni Ferrari
Keyword(s):  
Pediatric Patients ◽  
Calcium Deposition ◽  
Collagen Structure ◽  
Adult Rats ◽  
Rat Serum ◽  
Juvenile Rats ◽  
Adult Rat ◽  
Circulating Markers

Objective: Bioprosthetic heart valves (BHV) are subject to accelerated structural valve degeneration (SVD) in pediatric patients. Prior literature has reported differences in circulating markers of mineralization in pediatric patients compared to adults. Here we test the hypothesis that calcification-related circulating markers are differentially expressed in juvenile vs adult animals, and these markers functionally drive the accelerated SVD in juvenile animals in vitro and in vivo . Methods: Serum calcium (Ca 2+ ), phosphate (PO 4 - ), alkaline phosphatase (ALP), and osteopontin (OPN) levels of juvenile (3 week-old; n=5) and adult (8 month-old; n=5) Sprague-Dawley rats were measured by commercially-available assay kits. Glutaraldehyde-fixed bovine pericardial discs (BP) were incubated in juvenile or adult rat serum in vitro for 4 or 8 weeks. BP were subcutaneously implanted in juvenile or adult rats for 7 or 30 days (4-6 discs/rat). Pericardial transcatheter valves were implanted in juvenile Dorset sheep for 150 days (n=3). Alizarin Red staining, Von Kossa staining, and a quantitative assay were used for calcium analyses. Second harmonic generation imaging visualized collagen structure. Results: Serum Ca 2+ (p<0.05), PO 4 - (p<0.05), ALP (p<0.01), and OPN (p<0.01) were all increased in juvenile rats compared to adult rats. BP incubated in juvenile rat serum resulted in higher calcium deposition (p<0.05) and more disruption to collagen structure as evidenced by reduced alignment coefficient (p<0.01) as compared to those incubated in adult rat serum. Similarly, BP explanted from juvenile rats had higher calcium deposition (p<0.01) and more disrupted collagen structure in terms of collagen alignment and crimp period (p<0.01). Results in progress in juvenile sheep implantation model further confirmed the in vitro and in vivo findings that BHV explants had substantial calcium deposition and collagen disalignment. Conclusion: Calcium accumulates within BHV biomaterials more prominently in juvenile rats; increased serum markers of mineralization may explain the increased susceptibility to SVD in pediatric patients. Future studies will investigate novel strategies for the prevention and mitigation of accelerated SVD in pediatric patients.

scholarly journals Glutamine gluconeogenesis in the small intestine of 72 h-fasted adult rats is undetectable

2006 ◽  
Vol 401 (2) ◽  
pp. 465-473 ◽  
Author(s):  
Guy Martin ◽  
Bernard Ferrier ◽  
Agnès Conjard ◽  
Mireille Martin ◽  
Rémi Nazaret ◽  
...  
Keyword(s):  
Small Intestine ◽  
Glucose Production ◽  
Sprague Dawley ◽  
Adult Rats ◽  
Concentration Difference ◽  
Adult Rat ◽  
Nutrition And Diabetes ◽  
Glucose Synthesis

Recent reports have indicated that 48–72 h of fasting, Type 1 diabetes and high-protein feeding induce gluconeogenesis in the small intestine of adult rats in vivo. Since this would (i) represent a dramatic revision of the prevailing view that only the liver and the kidneys are gluconeogenic and (ii) have major consequences in the metabolism, nutrition and diabetes fields, we have thoroughly re-examined this question in the situation reported to induce the highest rate of gluconeogenesis. For this, metabolically viable small intestinal segments from 72 h-fasted adult rats were incubated with [3-13C]glutamine as substrate. After incubation, substrate utilization and product accumulation were measured by enzymatic and NMR spectroscopic methods. Although the segments utilized [13C]glutamine at high rates and accumulated 13C-labelled products linearly for 30 min in vitro, no substantial glucose synthesis could be detected. This was not due to the re-utilization of [13C]glucose initially synthesized from [13C]glutamine. Arteriovenous metabolite concentration difference measurements across the portal vein-drained viscera of 72 h-fasted Wistar and Sprague–Dawley rats clearly indicated that glutamine, the main if not the only gluconeogenic precursor taken up, could not give rise to detectable glucose production in vivo. Therefore we challenge the view that the small intestine of the adult rat is a gluconeogenic organ.

Circulating forms and biological activity of intact and truncated insulin-like growth factor I in adult and neonatal rats

1990 ◽  
Vol 123 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Katarina Drakenberg ◽  
Claes-Göran Östenson ◽  
Vicki Sara
Keyword(s):  
Biological Activity ◽  
Binding Proteins ◽  
Adult Rats ◽  
Igf Binding Proteins ◽  
Igf I ◽  
Igf Binding ◽  
Old Rats ◽  
In Vivo Administration

Abstract. A variant of IGF-I with a truncated aminoterminal region has been isolated and shown to display increased biological activity in vitro, but weak affinity of binding to the IGF binding proteins compared with intact IGF-I. In the present study, the circulating molecular forms and biological activity of intact and truncated IGF-I were compared after in vivo administration. Adult and 10-day-old rats were given 125I-truncated or 125I-intact IGF-I iv. In both adult and 10-day-old rats 125I-truncated IGF-I showed weaker affinity of binding to the IGF binding proteins and greater degradation than 125I-intact IGF-I. Serum half-life was 2 h for 125I-truncated IGF-I and 3 h for 125I-intact IGF-I in adult rats. The half-life in 10-day-old rats was 20.5 min for 125I-truncated IGF-I and 27 min for 125I-intact IGF-I. The uptake of 125I-truncated IGF-I into the kidney, liver and brain of 10-day-old rats was significantly higher than for 125I-intact IGF-I 15 min after iv administration. The insulin-like effects of the IGF-I peptides were examined in vitro and in vivo. Truncated IGF-I stimulated [3-3H]glucose incorporation into free fatty acids in adipocytes in vitro to a greater extent than did intact IGF-I. In vivo administration of both intact and truncated IGF-I to adult rats significantly decreased serum glucose levels and significantly increased the incorporation of [U-14C]glucose into glycogen. Thus, the present results demonstrated that truncated IGF-I displays reduced binding to the IGF binding proteins in vivo compared with intact IGF-I.

Comparison of the effects on purified Leydig cells of four hormones (oxytocin, vasopressin, opiates and LHRH) with suggested paracrine roles in the testis

1987 ◽  
Vol 113 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. M. Sharpe ◽  
I. Cooper
Keyword(s):  
Leydig Cells ◽  
Interstitial Fluid ◽  
Adult Rats ◽  
Adult Rat ◽  
Clear Cut ◽  
Testosterone Production ◽  
Time Period ◽  
High Doses

ABSTRACT Four hormones have been identified by various authors as possible paracrine regulators of testicular Leydig cells. The aim of this study was to evaluate their effects on purified adult rat Leydig cells under various conditions in vitro, and then to assess whether comparable effects occurred in vivo. In agreement with previous findings, an LHRH agonist (LHRH-A) exerted clear-cut effects on testosterone secretion by Leydig cells both in vitro and in vivo. On its own, LHRH-A stimulated testosterone production by Leydig cells for up to 24 h in culture but inhibited testosterone production stimulated by human chorionic gonadotrophin (hCG) between 24 and 72 h of culture. In-vivo, unilateral intratesticular injection of adult rats with 1 ng LHRH-A resulted 5 h later in a significant increase in testosterone concentrations in testicular interstitial fluid (IF). Vasopressin exerted effects in vitro which were similar to those of LHRH-A. On its own, vasopressin stimulated testosterone production for up to 5 h of culture, but not thereafter, while in the presence of hCG, vasopressin inhibited testosterone production beyond 24 h of culture. The initial stimulatory effect of vasopressin on testosterone production occurred with concentrations of 1 nmol/l and higher, but the magnitude of stimulation (threefold or less) was considerably less than that induced by LHRH-A (ninefold) over the same time period. In contrast to LHRH-A, unilateral intratesticular injection of vasopressin in high doses (20 and 2 ng) had no effect on IF testosterone levels 5 h later. When Leydig cells were cultured in the presence of testicular IF, to approximate in-vivo conditions, there was marked stimulation of testosterone production, but the effects of vasopressin and LHRH-A in the presence of IF were comparable to those observed in its absence. Neither morphine nor oxytocin at concentrations of 0·1 μmol/l had any effect on testosterone production under any of the conditions of culture, and unilateral intratesticular injection of oxytocin, morphine or naloxone was without effect on the IF levels of testosterone. It is concluded that opiates and oxytocin are probably not involved in the paracrine regulation of Leydig cells, whereas vasopressin may play such a role. However, as the stimulatory effects of vasopressin were small in relation to those of LHRH-A and were not evident in vivo, the physiological significance of the effects of vasopressin are uncertain. J. Endocr. (1987) 113, 89–96

GH receptor signaling in skeletal muscle and adipose tissue in human subjects following exposure to an intravenous GH bolus

2006 ◽  
Vol 291 (5) ◽  
pp. E899-E905 ◽  
Author(s):  
Jens O. L. Jørgensen ◽  
Niels Jessen ◽  
Steen B. Pedersen ◽  
Esben Vestergaard ◽  
Lars Gormsen ◽  
...  
Keyword(s):  
Dna Binding ◽  
Kinase Activity ◽  
Human Subjects ◽  
Binding Activity ◽  
In Vivo Model ◽  
Gh Receptor ◽  
Dna Binding Activity ◽  
Igf I

Growth hormone (GH) regulates muscle and fat metabolism, which impacts on body composition and insulin sensitivty, but the underlying GH signaling pathways have not been studied in vivo in humans. We investigated GH signaling in biopsies from muscle and abdominal fat obtained 30 ( n = 3) or 60 ( n = 3) min after an intravenous bolus of GH (0.5 mg) vs. saline in conjunction with serum sampling in six healthy males after an overnight fast. Expression of the following signal proteins were assayed by Western blotting: STAT5/p-STAT5, MAPK, and Akt/PKB. IRS-1-associated PI 3-kinase activity was measured by in vitro phosphorylation of PI. STAT5 DNA binding activity was assessed with EMSA, and the expression of IGF-I and SOCS mRNA was measured by real-time RT-PCR. GH induced a 52% increase in circulating FFA levels with peak values after 155 min ( P = 0.03). Tyrosine-phosphorylated STAT5 was detected in muscle and fat of all subjects after GH. Activation of MAPK was observed in several lysates but without GH dependency. Neither PKB/Akt nor PI 3-kinase activity was affected by GH. GH-induced STAT5 DNA binding and expression of IGF-I mRNA were detected in fat, whereas expression of SOCS-1 and -3 tended to increase after GH in muscle and fat, respectively. We conclude that 1) STAT5 is acutely activated in human muscle and fat after a GH bolus, but additional downstream GH signaling was significant only in fat; 2) the direct GH effects in muscle need further characterization; and 3) this human in vivo model may be used to study the mechanisms subserving the actions of GH on substrate metabolism and insulin sensitivity in muscle and fat.

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