PubMed Health⌕ Search

Biomedical subjects

M R Hammerman

Publications and source records attributed to M R Hammerman.

At least 55 records · Page 3Linked to original sources
PubMed1995

Growth factor gene expression in tubular epithelial injury.

In animal models of acute renal injury, administration of epidermal, insulin-like or hepatocyte growth factor accelerates restoration of kidney function and normalization of histology, and reduces mortality. Mechanisms for such action include stimulation of anabolism, maintenance of glomerular filtration, and enhancement of tubular regeneration. Further studies are needed to establish the utility of growth factors as therapeutic agents for acute renal failure in humans.

Acute Kidney Injury↗
PubMed1995

Triiodothyronine stimulates renal epidermal growth factor expression in adult rat.

To define the role that thyroid hormones play in regulation of renal epidermal growth factor (EGF) production, we characterized the effect of triiodothyronine (T3) administration on renal EGF expression in adult rats. The action of T3 to regulate EGF production was examined under one condition in which renal EGF expression is known to be diminished, posthypophysectomy, and in pituitary-intact rats. Levels of mature EGF, EGF precursor, and EGF mRNA, reduced in kidneys of hypophysectomized rats compared with pituitary-intact animals, increased significantly following the administration of T3 to hypophysectomized rats. Thus replacement of thyroid hormone alone was sufficient to enhance renal EGF expression. Induction of a hyperthyroid state in normal rats by injection of T3 for 4 days increased levels of extractable immunoreactive mature EGF, EGF precursor present in renal membranes, and EGF mRNA measured in kidneys. Levels of EGF in circulation were undetectable under all experimental conditions. We conclude that T3 enhances the renal synthesis of EGF in both hypopituitary and pituitary-intact rats. Enhancement of renal EGF expression is one mechanism that must be considered to explain the actions of thyroid hormones on kidney.

Animals↗
PubMed1995

Fulminant metanephric apoptosis and abnormal kidney development in bcl-2-deficient mice.

Apoptosis of the developing metanephric kidney plays an important role in renal organogenesis. The bcl-2 is an oncogene that inhibits apoptotic cell death in a variety of settings. The bcl-2 (-/-) mice complete embryonic development but, in contrast to bcl-2 (+/-) and bcl-2 (+/+) littermates, manifest growth retardation, hypopigmentation of hair, lymphoid apoptosis, abnormal kidney morphology, and renal failure postnatally. To provide insight into the mechanism for the latter abnormalities, we examined metanephric kidneys from bcl-2 (-/-), bcl-2 (+/-), and bcl-2 (+/+) mice, as well as embryonic day 12 (E12) mouse embryos, and compared growth and development of metanephroi in vitro. Kidneys from bcl-2 (+/-) mice developed normally. In contrast, development of kidneys from bcl-2 (-/-) mice was abnormal as reflected by a marked reduction of renal size in newborns compared with kidneys of bcl-2 (+/-) littermates. In addition, kidneys from bcl-2 (-/-) mice contained far fewer nephrons and had smaller nephrogenic zones. Although metanephroi obtained from E12 bcl-2 (+/-) and bcl-2 (-/-) mouse embryos were comparable in size, apoptosis of cells within metanephric blastemas of metanephroi from E12 bcl-2 (-/-) embryos was strikingly enhanced compared with that in blastemas of metanephroi from bcl-2 (+/-) embryos. During 3 days in culture, growth and development of metanephroi from bcl-2 (-/-) embryos were visibly reduced compared with those from bcl-2 (+/-) embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1995

Growth factors in renal development.

The formation of all organs during embryogenesis, including the kidney, is dependent on the timed and sequential expression of a number of polypeptide growth factors. Synthesis and actions of one or more members of the insulinlike growth factor (IGF), epidermal growth factor/transforming growth factor-alpha (EGF/TGF-alpha), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), hepatocyte growth factor (HGF), and nerve growth factor (NGF) families have been characterized in the developing metanephric kidney. Studies originating from a number of laboratories have defined the localization of growth factor mRNAs, receptors and peptides, have delineated patterns of growth factor synthesis, have established the growth factor-dependency of embryonic kidney development, and have identified abnormalities of growth factor-expression as potentially causative of aberrancies in metanephrogenesis. The results of these investigations are summarized in this review.

Animals↗
PubMed1994

Effects of IGF-I on renal function in end-stage chronic renal failure.

To determine whether insulin-like growth factor I (IGF-I) affects kidney function in patients with end-stage chronic renal failure, we administered recombinant human IGF-I (rhIGF-I) (100 micrograms/kg body wt subcutaneously twice daily) to nine individuals with baseline inulin clearances below 21 ml/min/1.73 m2. Four patients were treated for four days (short-term treatment) and five for periods between 13 and 27 days (long-term treatment). Administration of rhIGF-I increased inulin clearance, p-aminohippurate (PAH) clearance and the percent tubular reabsorption of filtered phosphate, and decreased plasma creatinine, blood urea nitrogen (BUN) and plasma phosphate during short-term administration. Kidney volume was unchanged in patients receiving the growth factor. rhIGF-I did not cause weight gain, proteinuria or hypoglycemia. Inulin clearance was not increased significantly above baseline after 13 or 20 days of IGF-I administration. PAH clearance remained elevated after 13 days, but not after 20 days of IGF-I. Levels of total circulating IGF-I were elevated above basal levels during the entire course of long-term IGF-I administration. In contrast, levels of circulating IGF binding protein 3 (IGFBP3) declined over time. Side effects related to IGF-I forced discontinuation of its use in two of five patients undergoing long-term treatment, and side-effects possibly related to IGF-I prompted discontinuation of its use in two others. We conclude that rhIGF-I can enhance glomerular filtration rate and renal plasma flow when administered short-term to humans with end-stage chronic renal renal failure. Further studies will be required to define its efficacy and usefulness long-term.

Adult↗
PubMed1994

Hepatocyte growth factor accelerates recovery from acute ischemic renal injury in rats.

Effects of hepatocyte growth factor (HGF) administration were examined in a model of acute ischemic renal injury induced by bilateral renal artery occlusion in rats. Compared with rats administered vehicle, rats administered 20 micrograms HGF subcutaneously 30 min postischemia had significantly lower serum creatinine and blood urea nitrogen levels over the course of 7 days postocclusion, enhanced insulin clearances measured on day 2 postocclusion, reduced mortality, and much less injury evident by examination of kidney histologies 7 days postinjury. The tubular regeneration that occurred postischemic injury was reflected by increased incorporation of 5-bromo-2'-deoxyuridine (BrdU) in cortical tubular epithelium compared with incorporation in kidneys from noninjured rats. HGF enhanced BrdU incorporation compared with vehicle, indicating enhanced mitogenesis. The weight loss that occurs postischemic injury was not ameliorated by the dose of HGF we employed. We conclude that administration of HGF postischemic injury to rats stimulates the recovery of normal kidney function and the regeneration of proximal tubular epithelium.

Animals↗
PubMed1994

Rat models for clinical use of insulin-like growth factor I in acute renal failure.

Insulin-like growth factor I (IGF-I) improves kidney function and histopathology, when given within a short time (0.5 or 5 h) after an ischemic renal insult in rats. To examine the effects of IGF-I at times that would be more applicable if it were to be used as a therapeutic agent for acute renal failure in humans, we administered IGF-I to rats 24 h after ischemic injury or prior to the induction of injury (pretreatment). In rats that received IGF-I 24 h postischemia, serum creatinine and blood urea nitrogen (BUN) values were significantly lower during the subsequent 6 days than in vehicle-treated rats, and incorporation of 5-bromo-2'-deoxyuridine into tubular cells of the regenerating cortex, measured 48 h postischemia, was enhanced. When examined 7 days postinjury, kidneys from rats that received IGF-I 24 h postischemia were improved in histopathological appearance compared with kidneys from vehicle-treated animals. Whereas creatinine and BUN values were elevated above baseline in both vehicle and IGF-I-pretreated groups, recovery of normal renal function was accelerated by pretreatment with IGF-I. In addition, although we could detect no differences in histopathology at 24 h postinjury, IGF-I pretreatment resulted in more normal renal histology at 7 days postischemic injury and reduced weight loss after injury. Our data show that IGF-I hastens recovery and accelerates regeneration or repair of damaged epithelia following acute renal failure in rats when administered either 24 h postinjury or prior to induction of acute renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1994

Effects of growth hormone on rat renal epidermal growth factor expression.

The kidney is a site of synthesis for several polypeptide growth factors including epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I). Interactions between growth hormone (GH) and growth factors have been described that regulate renal growth factor expression. For example, GH and EGF each enhances the expression of IGF-I in kidney. To further define interrelationships in this renal GH-growth factor axis, we characterized the effect of GH on renal EGF expression in hypophysectomized, pituitary-intact (normal) rats, and hypersomatotropic rats. Levels of extractable immunoreactive mature EGF, levels of a 142-kDa EGF-precursor present in renal membrane fractions, and levels of EGF mRNA were significantly reduced in kidneys from hypophysectomized rats compared with levels in normal rats. Each was increased significantly after the administration of GH to hypophysectomized rats. In contrast, induction of hypersomatotropism in normal rats by injection of GH for 17 days did not affect levels of extractable mature EGF or EGF mRNA measured in kidneys. We conclude that GH enhances the renal synthesis of EGF in hypopituitary, but not in hypersomatotropic states.

Animals↗
PubMed1994

Therapeutic use of growth factors in renal failure.

Polypeptide growth factors regulate kidney development, growth, and function and participate in processes of repair after renal injury. The use of one or more growth factors as therapeutic agents has been proposed in the settings of acute and chronic renal failure. In animal models of acute renal injury, the administration of epidermal growth factor, insulin-like growth factor I (IGF-I), or hepatocyte growth factor accelerates the restoration of kidney function and the normalization of histology post-acute renal injury and reduces mortality. The mechanisms by which the growth factors act in acute renal failure include the stimulation of anabolism, the maintenance of glomerular filtration, and the enhancement of tubular regeneration. IGF-I has been safely administered to humans with chronic renal failure. The growth factor enhances GFR and RPF in these individuals. Further studies will be required to establish a role for IGF-I or other growth factors as therapeutic agents for acute renal failure in humans and to define the utility of IGF-I as a medical therapy for chronic renal insufficiency.

Acute Kidney Injury↗
PubMed1993

Epidermal growth factor binding and stimulation of inositol trisphosphate production in basolateral membranes from dog kidney.

To ascertain whether epidermal growth factor (EGF) receptors are present in proximal tubular basolateral membranes from dog kidney and whether the growth factor activates phospholipase C at this site, we measured binding of 125I-EGF in isolated membranes and determined whether incubation of the membranes with EGF results in generation of inositol trisphosphate. Specific binding of 125I-EGF to basolateral membranes was observed that was half-maximally inhibited by approximately 7 x 10(-10) M EGF. The specific binding capacity of basolateral membranes for EGF averaged 45.9 fmol/mg protein. 125I-EGF was crosslinked to 2 proteins in basolateral membranes with M(r)s of 170,000 and 150,000. EGF stimulated phosphorylation of a 170,000 M(r) protein. Incubation of basolateral membranes with EGF stimulated inositol trisphosphate production in a concentration-dependent manner. We conclude that EGF activates a phospholipase C activity that cleaves phosphatidylinositol 4,5-bisphosphate within the basolateral membrane.

Animals↗
PubMed1993

Growth factors and kidney development.

The formation of the metanephric kidney is dependent upon the timed and sequential expression of a number of polypeptide growth factors. To shed light on the participation of members of the insulin-like growth factor (IGF) and epidermal growth factor/transforming growth factor-alpha (EGF/TF-alpha) families, we measured the synthesis of IGF-I, IGF-II, EGF and TGF-alpha by developing rat metanephroi in organ culture and determined the effect of anti-growth factor antibodies on growth and development. IGF-I, IGF-II and TGF-alpha were produced by metanephroi and released into culture media. We could detect no EGF. Inclusion of anti-IGF-I, anti-IGF-II, anti-IGF-II receptor or anti-TGF-alpha antibodies in organ cultures inhibited growth and development of metanephroi. Our findings suggest that both members of the IGF family and TGF-alpha are produced within the developing metanephros and promote renal organogenesis.

Animals↗
PubMed1993

Roles of growth hormone and growth factors in the pathogenesis and treatment of kidney disease.

Growth hormone and a number of polypeptide growth factors exert actions on renal development, growth, and metabolism and on repair processes following renal injury. There is increasing evidence that under selected circumstances, these agents play roles in the pathogenesis of kidney disease and that under others, they may be useful in its treatment. Growth hormone, platelet-derived growth factor, or transforming growth factor-beta may be causative of glomerulosclerosis. The reduction in epidermal growth factor expression within the kidney in the setting of acute ischemic injury could delay regeneration, and replacement may be therapeutic. Insulin-like growth factor I may play a role in the regenerative response to acute renal injury. Pharmacologic properties of growth hormone or insulin-like growth factor I to enhance glomerular filtration rate and renal plasma flow and to increase skeletal growth may be harnessable for treating chronic renal failure and its complications. It is likely that strategies designed to employ growth hormone or growth factors as pharmacologic agents or to block their activities will assume increasingly important roles in therapy for renal disease.

Animals↗
PubMed1993

Role of growth factors in regulation of renal growth.

It is clear that a number of growth factors are synthesized within the adult and the developing kidney. Compelling evidence exists that several of these agents orchestrate the nephrogenic process. A growing body of data supports roles for one or more of these agents in the adult kidney as regulators of renal function, growth, and repair processes. Growth factor expression may be the cause of glomerulosclerosis in one or more pathophysiological states. Our knowledge of the sites of growth factor synthesis and actions in the kidney and of the mechanisms by which growth factor synthesis is regulated and actions are exerted is rudimentary. Expansion of this knowledge base is likely to result in a greater understanding of renal disease mechanisms and thereby generate strategies by which kidney damage can be halted, prevented, or reversed.

Animals↗
PubMed1993

Effects of IGF-I on renal function in patients with chronic renal failure.

Insulin-like growth factor I (IGF-I) has been shown to increase glomerular filtration rate and renal plasma flow in rats and humans with normal renal function. However, rats with reduced renal function are resistant to these effects. To determine whether IGF-I affects glomerular filtration rate and renal plasma flow in humans with reduced renal function, we administered recombinant human IGF-I (rhIGF-I) to patients with moderate chronic renal failure. Four patients whose baseline inulin clearances were 21.9, 23.2, 34.9, and 55.1 ml.min-1.1.73 m-2 were placed on a 1 g.kg-1.day-1 protein diet and studied over a 10-day period (0-10). On days 4-7, 100 micrograms/kg of rhIGF-I was subcutaneously administered twice daily to the patients. The effects of rhIGF-I on levels of circulating IGF-I, inulin clearance, p-aminohippurate (PAH) clearance, kidney volume, plasma glucose, plasma and urine calcium and phosphate, and urine sodium and protein were determined. Administration of rhIGF-I increased levels of circulating IGF-I, inulin clearances, PAH clearances, and kidney size in each of the four patients receiving the growth factor. IGF-I did not cause weight gain, natriuresis, proteinuria, or hypoglycemia. Plasma calcium and phosphate were not affected by rhIGF-I. However, the percent tubular reabsorption of filtered phosphate was increased. We conclude that administration of rhIGF-I can enhance glomerular filtration rate and renal plasma flow at least in some humans with moderately reduced renal function. The enhancement is associated with an increase in kidney volume.

Adolescent↗
PubMed1993

Enhanced renal IGF-I expression following partial kidney infarction.

Renal insulin-like growth factor (IGF)-I expression is enhanced in tissue that remains following removal of kidney mass. To characterize the expression of renal IGF-I after reduction of kidney mass by partial unilateral infarction, we measured levels of IGF-I extracted from noninfarcted (remnant) renal tissue that remained after one-half unilateral kidney infarction that was performed without (1/2NX) or with (1 1/2NX) contralateral nephrectomy. Levels of IGF-I extracted from remnant renal tissue after 1/2NX increased significantly, peaking on day 3 after renal mass reduction, and then returned toward baseline. Steady-state levels of IGF-I mRNA were also elevated on day 3, suggesting that the increase in IGF-I results from enhanced synthesis. A similar pattern of increased extracted IGF-I and elevated IGF-I mRNA occurred after 1 1/2NX. Levels of IGF-I extracted from remnant renal tissue 3 days after 1 1/2NX were not higher than levels extracted from remnant tissue 3 days after 1/2NX, and both were higher than levels of IGF-I extracted from contralateral kidneys 3 days after unilateral nephrectomy. Therefore, levels of IGF-I did not correlate with the extent of reduction of renal mass per se. We conclude that partial renal infarction provides a stimulus to enhance IGF-I expression. Increased renal IGF-I must be considered in the interpretation of findings originating from use of remnant kidney models of chronic renal failure.

Animals↗
PubMed1993

Metanephric transforming growth factor-beta 1 regulates nephrogenesis in vitro.

Development of the metanephric kidney during embryogenesis is regulated by a number of polypeptide growth factors of renal origin. We have defined previously a role for insulin-like growth factors (IGF) I and II and for transforming growth factor (TGF)-alpha. To delineate the effect of TGF-beta 1, on renal organogenesis, we cultured metanephroi surgically dissected from 13-day-old rat embryos in serum-free chemically defined media. TGF-beta 1 mRNA was present in kidneys from 13-day-old rat embryos, and positive immunostaining for TGF-beta 1 could be demonstrated in cultured metanephroi. However, TGF-beta bioactivity could not be detected in media obtained from the metanephroi. Addition of 10(-9) M TGF-beta 1 to cultures inhibited tubulogenesis, but had no effect on synthesis of IGF-I or -II. Addition of anti-TGF-beta 1 antibodies to cultures accelerated tubulogenesis within the metanephric blastema. These findings establish the potential for TGF-beta 1 production within the rat metanephros during development in vivo. It is possible that this peptide exerts a negative control on the process of tubulogenesis within metanephric blastema and in this manner acts to shape the architecture of mature kidney.

Animals↗
PubMed1993

The growth hormone insulin-like growth factor axis in kidney revisited.

Studies characterizing actions of growth hormone (GH) and insulin-like growth factors (IGF) in kidneys of adult and developing animals and humans have provided a good deal of insight into the functions of these peptides. Although certain of the actions may be mediated directly by GH, most appear to result from effects of GH to increase levels of circulating IGF or IGF produced in kidney. In addition to GH, epidermal growth factor (EGF) enhances the renal synthesis of IGF-I. Enhancement of renal IGF-I expression is GH independent in compensatory hypertrophy. Stimulation of kidney IGF-I production also occurs in diabetes mellitus. Renal IGF-I production is elevated in these settings in the absence of changes in circulating IGF-I, consistent with a causative role of renal IGF-I for the accompanying increased glomerular filtration rate and kidney growth. Actions of IGF in kidney are initiated following binding of peptides to specific receptors. Receptor number may be altered during compensatory growth and in diabetes mellitus. In addition to IGF, several IGF binding proteins (IGFBP) are produced in kidney and are likely to both inhibit and enhance the actions of IGF in different circumstances through sequestration of peptides and regulation of peptide interactions with their receptors. Administration of IGF-I to rats following acute ischemic injury hastens the recovery of normal renal function and accelerates the regeneration of the damaged proximal tubular epithelium. IGF-I increases the glomerular filtration rate in humans with normal and reduced functional kidney mass. These findings establish the potential for use of this peptide as a therapeutic agent in the settings of acute and chronic renal failure.

Animals↗