A dose-response study of the effects of biosynthetic human growth hormone on formation and strength of granulation tissue

Dose-Response Study of Human Growth Hormone in Venous Ulcers: Influence on Healing and Synthesis of Collagen Types I and III

Objective:

To investigate the dose-response effect of topical human growth hormone on healing and local collagen synthesis and to study procollagen propeptides as markers of healing in chronic venous ulcers.

Design:

Double-blind, placebo-controlled study.

Setting:

Multicentre study, University Hospitals of Copenhagen, Denmark.

Patients:

Eighty-seven patients with chronic venous ulcers.

Interventions:

Solutions of growth hormone (Norditropin), 0.17 IU/ml, 1 IU/ml and 11.2 IU/ml, 0.1 ml/cm2/day, or placebo (groups 1–4) was administered daily except weekends for 6 weeks.

Main outcome measures:

Healing rates evaluated as weekly ulcer area reduction and complete healing. Local collagen synthesis was evaluated by measurement of the propeptides of collagen types I and III (PICP and PIIINP) in wound washings twice weekly during the first 3 weeks.

Results:

No significant difference in ulcer area reduction between the groups was seen, although patients treated with 0.17 IU/ml healed faster than the other groups ( p = 0.14). Nine (45%), five (29%), seven (31%) and six (31%) ulcers in groups 1–4 respectively were healed at follow-up ( p = 0.06–0.1, log rank test). PICP and PIINP increased by 21.4% per week, (14.5–28% per week) and 20.2% per week, (12.2–28.2% per week) respectively compared with placebo, p < 0.05. Both PIIINP and PICP at 3 weeks correlated significantly with the healing rates, r = 0.44, p < 0.001 and r = 0.34, p < 0.005.

Conclusion:

The study failed to demonstrate a significant influence on healing, whereas collagen synthesis was stimulated dose-dependently by growth hormone. Procollagen propeptides are sensitive markers of growth hormone action and may be useful markers of healing in clinical investigations in chronic venous ulcers. Lower doses of growth hormone should be considered in future studies.

Topical Human Growth Hormone Treatment of Chronic Leg Ulcers

In a double-blind placebo-controlled trial, 37 patients with chronic leg ulceration were randomized to receive either topical human growth hormone, 1 IU cm −2 ulcer area, 5 d per week, or placebo, in addition to a standard treatment (compression, hydrocolloid dressing). The two groups were broadly similar in age, sex, initial ulcer area and underlying aetiological variables. During the study 18 patients were withdrawn (six in the growth hormone group and 12 in the placebo group; NS). Eight of them did not complete the 2 weeks of treatment necessary to establish a healing rate and were consequently not included in the analyses of healing. During a mean treatment period of 8 weeks, the healing rate was 16% per week (95% confidence interval 8.7 to 23% per week) in the growth hormone group and 3% per week (−3.4 to 8.4% per week) in the placebo group, ( P = 0.02). In 11 patients (61%) in the growth hormone group and two patients (18%) in the placebo group, the ulcer area decreased by 50% during the study ( P = 0.03). The treatment was neither accompanied by side-effects nor signs or symptoms indicating a significant absorption of growth hormone. Further studies are needed to address the dose-response relationship and optimal administration frequency of topical growth hormone in the treatment of chronic leg ulcers.

Epidermal homeostasis: the role of the growth hormone and insulin-like growth factor systems

GH and IGF-I and -II were first identified by their endocrine activity. Specifically, IGF-I was found to mediate the linear growth-promoting actions of GH. It is now evident that these two growth factor systems also exert widespread activity throughout the body and that their actions are not always interconnected. The literature highlights the importance of the GH and IGF systems in normal skin homeostasis, including dermal/epidermal cross-talk. GH activity, sometimes mediated via IGF-I, is primarily evident in the dermis, particularly affecting collagen synthesis. In contrast, IGF action is an important feature of the dermal and epidermal compartments, predominantly enhancing cell proliferation, survival, and migration. The locally expressed IGF binding proteins play significant and complex roles, primarily via modulation of IGF actions. Disturbances in GH and IGF signaling pathways are implicated in the pathophysiology of several skin perturbations, particularly those exhibiting epidermal hyperplasia (e.g., psoriasis, carcinomas). Additionally, many studies emphasize the potential use of both growth factors in the treatment of skin wounds; for example, burn patients. This overview concerns the role and mechanisms of action of the GH and IGF systems in skin and maintenance of epidermal integrity in both health and disease.

Contribution of circulating IGF-I to wound repair in GH-treated rats

Systemic administration of growth hormone (GH) stimulates granulation tissue formation, increases collagen deposition, improves the breaking strength of incisional wounds, and decreases donor-site healing times in burn patients. The possible role for circulating IGF-I in mediating this effect of growth hormone has not been investigated. To assess the relative effects of systemic IGF-I and GH on dermal repair, incisional wounds were created on the backs of male Sprague-Dawley rats treated with GH, or IGF-I or a combination of GH and IGF-I. After 7 days of treatment, wound strips were taken for wound strength and immunohistochemical analysis. Uninjured skin and liver samples were collected for mRNA analysis and plasma samples were taken at the completion of the experiment to determine circulating IGF-I levels. Increased circulating IGF-I levels and increased weight gain were observed only in the IGF-I and IGF-I+GH treatment groups, although steady-state igf-I levels were not altered in liver and uninjured skin after 7 days in any treatment group. IGF-I treatment had no positive effects on wound repair. Wound strength was increased with GH treatment only and associated with an increase in the intensity of IGF-I immunostaining in the granulation tissue of GH-treated animals. In line with the wound strength data, co-administration of IGF-I resulted in the decreased intensity of IGF-I immunostaining. We conclude that the GH-stimulated increase in wound strength is not mediated via endocrine-derived IGF-I and that only locally produced IGF-I acting in an autocrine or paracrine fashion contributes to the regulation of the wound repair process.

The effect of equine recombinant growth hormone on second intention wound healing in horses

OBJECTIVE

To evaluate the effect of intramuscular administration of recombinant equine growth hormone on healing of full thickness skin wounds on equine limbs.

STUDY DESIGN

Experimental.

ANIMALS

Nine Standardbred horses.

METHODS

In study 1, standardized full thickness skin wounds (2.5 x 2.5 cm) were made over the dorsomedial aspect of the mid-cannon bone of 1 forelimb and 1 hindlimb in 9 horses. Wounds were bandaged without treatment (control subjects) and videorecorded twice weekly until healed. Then, in study 2, similar wounds were created on the opposite limbs; 6 horses were administered intramuscular recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days), and 3 horses (control subjects) were administered equivalent volumes of sterile water. Wounds were videorecorded twice weekly until healed. Wound healing variables were measured from the videorecordings using a computer software package and analyzed as a randomized complete block design factorial analysis of variance; significance was set at P <.05.

RESULTS

No differences in the measured variables were detected between wounds in study 1 and the control wounds in study 2. In recombinant equine growth hormone-treated horses, wounds retracted more during treatment and contracted faster after treatment stopped when compared with wounds from untreated horses. No other treatment effects were detected.

CONCLUSIONS

Recombinant equine growth hormone seemingly increases wound retraction. After treatment ceases, wound contraction increases.

CLINICAL RELEVANCE

Intramuscular administration of recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days) does not appear to have any beneficial clinical effect on healing of equine limb wounds.

Sustained release of human growth hormone (hGH) from collagen film and evaluation of effect on wound healing in db/db mice

Collagen films containing human growth hormone (hGH) were prepared and the release of hGH from these films and their effect on healing of full-thickness wounds in db/db mice were evaluated. The release profiles of hGH from the collagen films varied with composition and preparation conditions. The film prepared by air-drying of the mixture of hGH and collagen solution released hGH continuously over 3 days both in vitro and in vivo. By application of collagen film containing 3 mg of hGH twice at an interval of 6 days to wounds, area of wounds on day 21 was significantly reduced compared with that of non-treated wounds. Application of hGH alone at the same dose had no significant effect on wound healing. The maximum serum hGH concentration after single administration of the hGH collagen film was lower than that with hGH alone, and hGH persisted in serum over 3 days. These results suggest that hGH collagen film may be a useful topical formulation for the treatment of wounds.

Growth hormone does not attenuate the inhibitory effects of sepsis on wound healing

Chronic abdominal sepsis is associated with impaired tissue repair. Treatment of burn patients with growth hormone results in improved healing of skin graft donor sites. The goal of this study was to determine whether administration of growth hormone could attenuate the inhibitory effects of sepsis on cutaneous wound healing. Four groups of male Sprague Dawley rats were studied: control, control + growth hormone, sepsis, and sepsis + growth hormone. Sepsis was caused by implantation of a bacterial focus in the peritoneal cavity. Control animals underwent sham laparotomy, and polyvinyl alcohol sponge implants were placed in subdermal pockets in all animals. Saline or growth hormone (400 microg) was injected subcutaneously every 12 hours. On day 5, the incisional wounds and polyvinyl alcohol sponge implants were harvested. The breaking strength of abdominal incisions was measured. Granulation tissue penetration and quality were determined by scoring polyvinyl alcohol sponge implant histology from 1 to 4 in a blinded fashion. Collagen deposition in polyvinyl alcohol sponge implants was quantitated by hydroxyproline assay. Septic mortality was not altered by growth hormone administration. Septic animals showed a reduction in food consumption for 2 days after surgery (p < 0.05 vs. controls), which was not affected by growth hormone administration. The breaking strength of incisional wounds and hydroxyproline content of polyvinyl alcohol sponge implants was reduced in septic rats (p < 0.001 vs. controls) but administration of growth hormone for 5 days did not improve breaking strength or collagen deposition in either group. We conclude that the administration of growth hormone for 5 days did not improve collagen deposition or breaking strength in cutaneous wounds from control or septic animals. The results suggest that growth hormone treatment is unlikely to improve tissue repair in sepsis-induced catabolic illness.

Effect of the environment on fetal skin wound healing

Skin wound healing has been shown to be a different process in the fetus than in the adult animal. Some of these differences have been attributed to the unique fetal environment (i.e., amniotic fluid). The aim of the present study is to compare fetal skin healing in intraamniotic and extraamniotic wounds. A fetal rabbit model has been used in which three types of skin wounds were induced on 23-day-old fetuses in contact with either amniotic fluid or maternal peritoneal fluid. The wounds consisted of a sutured skin incision, a nonsutured incision, and an electrocautery burn. Seven days later all wounds were examined mechanically (scar resistance), biochemically (collagen and noncollagen protein concentration), and histologically. Biochemical and growth factor studies of both environments, the amniotic and the peritoneal fluids, were also conducted. The results showed excellent healing by first intention and absence of healing by second intention in both environments, greater scar resistance in the intraperitoneally positioned fetal wounds, and a higher concentration of insulin-like growth factor-1 (IGF-1) in the peritoneal fluid than in the amniotic fluid. It can be concluded that fetal skin wounds in contact with peritoneal fluid show the same healing pattern as in the natural fetal environment (amniotic fluid). The higher concentration of IGF-1 in the peritoneal fluid suggests that this growth factor, through its relationship with the growth hormone, plays a role in increasing the scar resistance of fetal skin wounds in contact with maternal peritoneal fluid.

Current treatment of severely burned patients

OBJECTIVE

The authors provide an update on a multidisciplinary approach to the treatment of severely burned patients. A review of studies and clinical trials from the past to the present include fluid resuscitation, sepsis, immune function, hypermetabolism, early excision, wound healing, scar formation, and inhalation injury.

SUMMARY BACKGROUND DATA

Advances in treating initial burn shock, infection control, early wound closure, and modulation of the hypermetabolic response have decreased morbidity and mortality in the last two decades. Specialized burn care centers, using a multidisciplinary approach, not only successfully treat large burns and their complications, but provide the necessary rehabilitation and psychological support required for readjustment back into society.

CONCLUSIONS

Thermal injury results in a number of physiologic alterations that can be minimized by adequate fluid resuscitation to maintain tissue perfusion, early excision of burn wounds, and rapid wound coverage. These measures, in combination with antibiotic coverage and nutritional support in the form of early enteral tube feedings, will decrease the hypermetabolic response and the incidence of sepsis that can lead to hemodynamic instability and organ failure. Ongoing clinical trials using anabolic agents (e.g., recombinant human growth hormone) and pharmacologic agents that modulate inflammatory and endocrine mediators (e.g., ibuprofen and propranolol) show promise in the treatment of severe burn injuries.

Effects of growth factors and L-arginine on ischemic skin flaps in rats

This study determined the effect of the polypeptide growth factors transforming growth factor-beta (TGF-beta), insulin-like growth factor-I (IGF-I), and growth hormone (GH) alone and in combination with dietary L-Arginine HCL (ARG) on skin flap survival in rats. Caudally based dorsal skin flaps were created in 110 Sprague-Dawley rats. The rats were randomly assigned into three treatment groups, based on drinking water supplementation. Group 1 (n = 50) received ARG in their drinking water, group 2 (n = 50) received tap water alone, and group 3 (n = 10) received N-omega-nitro-L-arginine (L-NA) and hydralazine. Groups 1 and 2 were divided into subgroups of 10 rats each based on treatment with either: TGF-beta, IGF-I, GH, or IGF-I + GH. All subgroups that received GH had significantly greater (P < .0001) median body weight gains when compared with subgroups not receiving GH. L-arginine HCL when added to IGF-I negated the positive effects of IGF-I on both flap survival and weight gain. Although the rats in all subgroups from groups 1 and 2 had an increase in mean percent skin flap survival when compared with the water alone subgroup, only rats receiving IGF-I, or the combination of ARG with either TGF-beta or GH, had statistically significant enhanced skin flap survival. Rats in group 3 did not show an increase in skin flap survival when compared with the control subgroup.

Topical zinc oxide treatment increases endogenous gene expression of insulin-like growth factor-1 in granulation tissue from porcine wounds

Application of zinc oxide has been shown to accelerate the healing of both chronic and acute wounds, but the mechanisms are unknown. We quantified the gene expression (mRNA) for one important growth factor, insulin-like growth factor-1 (IGF-1) in 12 full-thickness wounds in each of three domestic pigs treated with or without topical zinc oxide. We used a RNAase protection/solution hybridisation technique to measure IGF-1 mRNA concentrations, which were 50% higher in the granulation tissue in wounds treated with zinc oxide compared with control wounds on days 3-4 (p < 0.05), but not thereafter (up to postoperative day 11). Topical zinc oxide increased the healing rate of wounds compared to the control group (p < 0.01). The cell composition of the granulation tissue was similar in the two groups. The increased gene expression of IGF-1 may be one mechanism by which topical zinc oxide enhances wound healing.

Growth hormone therapy initiated before starvation ameliorates the catabolic state and enhances the protein-sparing effect of total parenteral nutrition

The effect of 7 days of subcutaneously administered bovine growth hormone (bGH) (0.2 mg kg-1 day-1; n = 4) or an equivalent volume of 0.15 mol l-1 saline (n = 3) on protein metabolism was assessed in lambs. The catabolic response to 48 h of starvation and subsequent hypocaloric total parenteral nutrition (TPN) was measured using primed constant intravenous infusions of [15N]urea and [14C]leucine. Following 48 h of starvation and 7 h of TPN, bGH-treated animals had a significantly decreased rate of net protein catabolism compared with controls (mean(s.e.m.) 2.4(0.2) versus 3.2(0.3) g kg-1 day-1, P < 0.01). The mean(s.e.m.) rate of whole-body protein catabolism was also significantly decreased in bGH-treated animals at 10.9(0.3) g kg-1 day-1 compared with 12.9(0.7) g kg-1 day-1 in saline-treated controls (P < 0.05). In addition, the rates of net and whole-body protein catabolism decreased significantly (P < 0.05) during the period of hypocaloric parenteral feeding to mean(s.e.m.) values of 2.3(0.2) and 8.6(0.6) g kg-1 day-1 respectively in bGH-treated animals. By contrast, in saline-treated controls net and whole-body protein catabolism continued to increase during hypocaloric parenteral feeding. There was a significant decrease (P < 0.05) in the rate of [14C]leucine uptake in tissues of the gastrointestinal tract, heart and diaphragm in bGH-treated animals compared with controls. These results demonstrate that daily administration of growth hormone decreases the catabolic response to a metabolic stress, resulting in the conservation of protein in the heart, diaphragm, gastrointestinal tract and musculoskeletal system by a primary anticatabolic action. In addition, growth hormone therapy initiated before induction of the catabolic state enhances the protein-sparing effects of TPN. Further study is justified to determine whether growth hormone therapy initiated before elective or urgent surgery in the nutritionally depleted patient may have a role in reducing the severity of the postoperative catabolic state, particularly in the patient in whom a complicated course is anticipated.

Effect of N-terminal modified analogs of growth hormone on collagen synthesis in avian skin fibroblasts

Human growth hormone (hGH) inhibits alpha 1(I) collagen gene expression in cultured avian skin fibroblasts resulting in a decrease in the amount of collagenase-digestible proteins (CDP) in the medium. In addition, a synergism exists between GH and insulin-like growth factor-I (IGF-I) in their effect on CDP. Four N-terminal modified hGH analogs were tested for their ability to affect collagen metabolism in these cells. The truncated analog Des-7 hGH(R8M, D11A) was found to be a strong antagonist of the hGH-induced inhibition of the collagen synthesis but by itself did not inhibit collagen alpha 1(I) gene expression or modify the CDP appearance in the medium. Some synergism between Des-7 hGH and IGF-I was observed. The analog Met-hGH(R19H, L20P), in which Arg19 was replaced by histidine, and Leu20 by proline was only partially potent compared with the native hormone in causing inhibition of collagen gene expression, in attenuating CDP appearance in the medium, and in antagonizing hGH. However, this analog was as potent as hGH in its ability to synergize with IGF-I. The importance of His18 was assessed by testing the response to Met-hGH(H18D), in which His18 was replaced by Asp, and to Met-hGH(H18Q), in which His18 was replaced by glutamine (as in chicken GH sequence). Substitution of His18 by a negatively charged amino acid abolished all the hormone activities tested whereas substitution with glutamine restored only part of the activity.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo activation of circulating monocytes by exogenous growth hormone in man

Animal studies have shown that administration of growth hormone improves wound healing. Monocyte activation is a prerequisite for optimal repair of damage. In vitro, human recombinant growth hormone was shown to be a potent human monocyte chemoattractant. It induced random migration and chemotaxis at picomolar concentrations of recombinant human growth hormone; combinations of growth hormone with other chemoattractants deactivated the chemotactic response. Other functions of monocytes that are activated by growth hormone include release of superoxide anion and production of cytokines. In order to test activation of human monocytes by growth hormone in vivo, we investigated the effects of recombinant human growth hormone administration on monocyte migration in nine healthy young adults. After a single dose of recombinant human growth hormone (4 IU subcutaneously injected), random migration of circulating monocytes significantly increased, whereas chemotaxis of monocytes that was maximally stimulated with f-Meth-Leu-Phe decreased (p < .05). The alterations paralleled the concomitantly measured plasma levels of growth hormone. After recombinant human growth hormone administration, no changes were seen in plasma levels of proinflammatory cytokines. These in vivo data on monocyte migration are comparable to effects of growth hormone on monocyte migration in vitro and strongly suggest that recombinant human growth hormone can activate circulating monocytes in man.

The effect of insulin-like growth factor-I and human growth hormone on periodontal ligament fibroblast morphology, growth pattern, DNA synthesis, and receptor binding

Repopulation of the detached root surface by cells from the periodontal ligament (PDL) is a prerequisite for new attachment formation. Stimulation of PDL-cell growth may therefore serve as an essential method to enhance formation of new attachment. Studies have demonstrated that insulin-like growth factor-I (IGF-I) has a mitogenic effect on fibroblasts originating from various connective tissues and cell-lines. Further, human growth hormone (hGH) is known to regulate the plasma concentration of IGF-I and to mediate cellular biological effects. In the present study we examined the effect of IGF-I and hGH on morphology, growth pattern, and DNA synthesis. The expression of IGF-I and hGH receptors on the surface of cultured PDL fibroblasts is also described. A primary fibroblastic cell line was established from rat PDL tissue, and blind, photographic recordings of morphology and growth pattern, as well as incorporation of [3H]thymidine in cellular DNA, was carried out in the presence and absence of IGF-I and hGH. The presence of specific membrane receptors was investigated by binding of [125I]IGF-I and [125I]hGH. The analysis of photographs showed that IGF-I and hGH had no effect on morphology and growth pattern. Incorporation of 3H-thymidine, however, was increased in a dose-dependent manner by IGF-I, whereas hGH alone or in combination with IGF-I produced no dose-dependent response. Maximum effect (% of control) on DNA synthesis was 176% for IGF-I and 91% for hGH.(ABSTRACT TRUNCATED AT 250 WORDS)

Collagen types I and III propeptides as markers of healing in chronic leg ulcers. A noninvasive method for the determination of procollagen propeptides in wound fluid--influence of growth hormone

A noninvasive method allowing measurements of the propeptides of collagen type III (PIIINP) and type I (PICP) in ulcer washings was developed. The response to topical human growth hormone was examined. Fourteen patients with venous ulcers were treated sequentially with human growth hormone (0.1, 0.25, and 1 IU/cm2/day), each dose for 1 week, followed by 1 week washout. On alternate days, three and two times during treatment and washout periods, respectively, the ulcers were washed and incubated for 30 minutes with sterile water. No changes in healing rates in relation to growth hormone application were observed. In contrast, PIIINP increased significantly to 168% (154% to 184%) (mean, 95% confidence interval) and 195% (179% to 218%) 5 and 9 days, respectively, after start of treatment, (p < 0.01). Propeptides of collagen type I reached a significant increase, to 196% (172% to 232%), in the fourth week, (p < 0.01). The areas under the curves of PICP and PIIINP correlated significantly with the healing rates (r = 0.57, p = 0.04; and r = 0.64, p = 0.01, respectively). The authors conclude that propeptide measurements may be useful markers of healing in clinical studies.

Growth hormone and insulin-like growth factor I regulate collagen gene expression and extracellular collagen in cultures of avian skin fibroblasts

Avian skin fibroblasts were isolated, cultured and incubated with [3H]proline for 24 h. The cells exported radiolabeled collagenase-digestible (CDP) and non-collagenase-digestible (NCDP) proteins into the medium. Human, bovine and avian growth hormone (GH) as well as insulin-like growth factor I (IGF-I) attenuated the appearance of [3H]CDP in the medium without affecting [3H]NCDP. The appearance of [3H]CDP was not affected by prolactin. The effects of GH and IGF-I were enhanced by increasing concentrations of fetal calf serum (FCS). A synergism was observed between GH and IGF-I in their effect on CDP. Each peptide, at an ineffective concentration, increased the sensitivity of the cells to the other peptide. Collagenase activity in the medium was enhanced by IGF-I, but not modified by GH, FCS, or by their interaction with IGF-I. GH and IGF-I inhibition of type I procollagen gene expression was demonstrated with the aid of probes containing sequences corresponding to the mRNAs for avian alpha I and alpha II chains. The results suggest that GH and IGF-I cooperate in regulating collagen synthesis, but collagen degradation is affected by IGF-I and not by GH.

Alterations in the cross-links of skin collagen of rats treated with biosynthetic growth hormone

The effect of biosynthetic human growth hormone (b-hGH) treatment on rat skin collagen was investigated. Groups of rats were injected with b-hGH 0.16, 1.10 and 8.33 mg/kg/day for 90 days. The weight gain of the rats treated with b-hGH 1.10 and 8.33 mg/kg/day was 13% and 82% higher, respectively, compared with that of the placebo control group. The extractability of the skin collagen was studied by extraction with phosphate buffered saline (pH 7.4), followed by acetic acid (0.5 M) and acetic acid with pepsin. The reducible collagen cross-links were measured after reduction of the cross-links by KB3H4, followed by acid hydrolysis and ion-exchange chromatography. Furthermore, patterns of cyanogen bromide peptides were studied by SDS-poly-acrylamide-gel-electrophoresis. Peptides bound together by stable cross-links and the relative amounts of collagen type I and collagen type III were measured. Treatment with b-hGH 8.33 mg/kg/day resulted in increased extractability of the skin collagen in acetic acid, increased relative amounts of reducible collagen cross-links and reduced amounts of high molecular weight cyanogen bromide cleaved peptides of the collagen. These alterations probably reflect an increased synthesis of skin collagen induced by the highest dose of b-hGH. The relative amounts of collagen type I and collagen type III of the skin were not influenced by the b-hGH treatment.

The influence of aminoguanidine on borohydride reducible collagen cross-links and wound strength

The mechanical strength of skin wounds as well as the deposition of hydroxyproline and KB3H4 reducible hydroxylysinonorleucine (HLNL) and dihydroxylysinonorleucine (DHLNL) cross-links in subcutaneously implanted cellulose sponges have been investigated in rats treated with aminoguanidine (AG) or beta-aminopropionitrile (BAPN). Treatment with AG (25 mg/kg BW/day) did not influence the mechanical strength of the wounds, the deposition of hydroxyproline or the pattern of reducible collagen cross-links, whereas AG (125 mg/kg BW/day) reduced the maximum load by 17%, but did not influence the deposition of hydroxyproline or reducible cross-linking pattern. Treatment with BAPN (333 mg/kg BW/day) reduced the strength of the wounds by 59%, the HLNL by 50% and the DHLNL 57%, whereas the deposition of hydroxyproline did not seem to be influenced by BAPN treatment. In conclusion, AG at moderate dosage does not seem to influence the formation of lysyl oxidase dependent reducible cross-links of collagen.

Growth hormone increases the mass, the collagenous proteins, and the strength of rat colon

The effect of growth hormone treatment on the left colon was investigated in 4-month-old Wistar rats. The animals were injected with saline (controls) or biosynthetic human growth hormone (b-hGH) in doses of 1.0 and 5.0 mg b-hGH/kg/day for 30 days. The total body weight of the rats injected with 1.0 mg b-hGH/kg/day did not differ from that of the control group, whereas the body weight of the rats injected with 5.0 mg b-hGH/kg/day was increased by 37% compared with the control group. The colonic dry weight per unit length was increased by 57% and 46% by 1.0 mg and 5.0 mg b-hGH/kg/day, respectively. The defatted dry weight was increased by 52% and 44%, respectively. The hydroxyproline content per unit length was increased by 31% and 23%, respectively. Furthermore, the biomechanical strength was increased by the b-hGH injections. No difference between the two b-hGH doses was found in any of the data.

An investigation of the anabolic activity of somatropin in normal and burned rats

A 'blind', cross-over study was performed in 10 control and 12 burned rats which were assigned to receive either biosynthetic human growth hormone (somatropin) or placebo for 5 days each in random order. There was a significant rise in urinary nitrogen excretion and rapid weight loss in the burned rats, which also had significantly lower plasma somatomedin levels than control rats. Somatropin administration resulted in a significant increase in somatomedin levels in control rats only. There was no significant difference in weight or nitrogen balance between somatropin or placebo-treated rats. It is concluded that rats with normal pituitary function are insensitive to the anabolic effects of somatropin and that burn injury abolishes the normal somatomedin response to somatropin.

Dose response of growth hormone on fracture healing in the rat

The effect of different doses of biosynthetic human growth hormone on the mechanical properties of tibial fractures and intact bones was studied in a rat model; a three-point bending test was applied 40 days after fracturing. Ninety-day-old female rats received a daily dose of 0, 0.08, 0.4, 2.0, or 10 mg of growth hormone/kg body weight starting 1 week before fracture and continuing until mechanical testing. In the animals given 2.0 and 10 mg of hormone, the ultimate load sustained by the fractures, stiffness, and energy absorption at ultimate load increased, while the ultimate stress increased only in the latter groups. In the intact bones, ultimate load of the bones increased in the same groups, while stiffness and energy absorption at ultimate load increased only in the group given the highest dose of hormone.

Increased mechanical strength of healing rat tibial fractures treated with biosynthetic human growth hormone

The effects of biosynthetic human growth hormone on the biomechanical properties of healing tibial fractures and intact bones in the rat were studied after 20 and 40 days of healing. Growth hormone, 2.0 mg per kg per day, was given subcutaneously in two daily doses. Control animals were injected with a corresponding volume of saline. After 20 days of fracture healing, there were no differences in mechanical properties between the healing fractures and intact bones. After 40 days, the ultimate load and maximum stiffness of the fractures of the b-hGH injected animals had increased to more than 400% of the corresponding values of the saline injected animals, and ultimate stress and energy absorption at ultimate load had increased to 270% compared with the saline injected animals. Ultimate load, stiffness, and energy absorption of the intact bones increased in the b-hGH injected animals, but no differences were found in ultimate stress values or normalized energy, indicating that the changes in the intact bones were quantitative phenomena.