EGF-GH Axis in Rat Steatotic and Non-steatotic Liver Transplantation From Brain-dead Donors.

BACKGROUND: We evaluated the potential dysfunction caused by changes in growth hormone (GH) levels after brain death (BD), and the effects of modulating GH through exogenous epidermal growth factor (EGF) in steatotic and nonsteatotic grafts. METHODS: Steatotic and nonsteatotic grafts from non-BD and BD rat donors were cold stored for 6 hours and transplanted to live rats. Administration of GH and EGF and their underlying mechanisms were characterized in recipients of steatotic and nonsteatotic grafts from BD donors maintained normotensive during the 6 hours before donation. Circulating and hepatic GH and EGF levels, hepatic damage, and regeneration parameters were evaluated. Recipient survival was monitored for 14 days. Somatostatin, ghrelin, and GH-releasing hormones that regulate GH secretion from the anterior pituitary were determined. The survival signaling pathway phosphoinositide-3-kinase/protein kinase B that regulates inflammation (suppressors of cytokine signaling, high-mobility group protein B1, oxidative stress, and neutrophil accumulation) was evaluated. RESULTS: BD reduced circulating GH and increased GH levels only in steatotic livers. GH administration exacerbated adverse BD-associated effects in both types of graft. Exogenous EGF reduced GH in steatotic livers, thus activating cell proliferation and survival signaling pathways, ultimately reducing injury and inflammation. However, EGF increased GH in nonsteatotic grafts, which exacerbated damage. The benefits of EGF for steatotic grafts were associated with increased levels of somatostatin, a GH inhibitor, whereas the deleterious effect on nonsteatotic grafts was exerted through increased amounts of ghrelin, a GH stimulator. CONCLUSIONS: GH treatment is not appropriate in rat liver transplant from BD donors, whereas EGF (throughout GH inhibition) protects only in steatotic grafts.

The impact of nandrolone decanoate and growth hormone on biosynthesis of steroids in rats.

Growth hormone (GH) and anabolic androgenic steroids (AAS) are commonly used in sports communities. Several studies have suggested an association between GH and AAS. We have investigated the impact of GH in rats treated with nandrolone decanoate (ND). Male Wistar rats received ND (15 mg/kg) every third day during three weeks and were subsequently treated with recombinant human GH (1.0I U/kg) for ten consecutive days. Plasma samples were collected and peripheral organs (i.e. heart, liver, testis and thymus) were dissected and weighed. Concentration of thirteen endogenous steroids was measured in the rat plasma samples using high specificity LC-MS/MS methods. Seven steroids were detected and quantified, and concentrations of estrone, testosterone, and androstenedione were significantly different among the groups, while concentrations of pregnenolone, DHEA, 17-hydroxyprogesterone and corticosterone were not altered. Administration of rhGH alone altered the plasma steroid distribution, and the results demonstrated significantly increased concentrations of plasma estrone as well as decreased concentrations of testosterone and androstenedione in the ND-treated rats. Administration of rhGH to ND-pretreated rats did not reverse the alteration of the steroid distribution induced by ND. Administration of ND decreased the weight of the thymus, and addition of rhGH did not reverse this reduction. However, rhGH administration induced an enlargement of thymus. Taken together, the plasma steroid profile differed in the four groups, i.e. control, AAS, rhGH and the combination of AAS and rhGH treatment.

Effects of growth hormone and ultrasound on mandibular growth in rats: MicroCT and toxicity analyses.

It has been shown by previous studies that mandibular growth can be enhanced by the systemic administration of recombinant growth hormone (rGH) and/or local application of therapeutic low intensity pulsed ultrasound (LIPUS). The purpose of this study was to determine if local injection of rGH and application of LIPUS to the temporomandibular joint (TMJ) would synergistically enhance mandibular growth. In an animal study, the effect of rGH, LIPUS, and combination of rGH and LIPUS on male Sprague-Dawley rats was observed. Mandibular growth was evaluated by measuring total hemimandibular and condylar bone volume and bone surface area as well as condylar bone mineral density (BMD) after 21 days on dissected rats' mandibles using micro-computed tomography (MicroCT). The expression of c-jun mRNA extracted from the liver of each of these rats was also quantified by real-time polymerase chain reaction to evaluate possible systemic effect of local rGH administration. Significant growth stimulation was observed in the mandibular and condylar bone of the animals treated with rGH, LIPUS, and rGH/LIPUS combined when compared with the control group. Bone volume, surface area, condylar bone mineral density, and c-jun expression were also compared between the treatment groups and the control in the liver. The results suggest that mandibular growth may be enhanced by injection of rGH or LIPUS application. The current study although showed synergetic effect of rGH and LIPUS application in increasing mandibular condylar head length, there was no significant changes in mandibular bone volume using both treatments together when compared to the two individual treatments. Moreover, combined rGH and LIPUS decreased condylar bone mineral density than each treatment separately. Future research could be directed to investigate the effects of different rGH doses and/or different LIPUS exposures parameters on lower jaw growth.

Immunogenicity, toxicology, pharmacokinetics and pharmacodynamics of growth hormone ligand-receptor fusions.

A fundamental concern for all new biological therapeutics is the possibility of inducing an immune response. We have recently demonstrated that an LR-fusion (ligand-receptor fusion) of growth hormone generates a potent long-acting agonist; however, the immunogenicity and toxicity of these molecules have not been tested. To address these issues, we have designed molecules with low potential as immunogens and undertaken immunogenicity and toxicology studies in Macaca fascicularis and pharmacokinetic and pharmacodynamic studies in rats. Two variants of the LR-fusion, one with a flexible linker (GH-LRv2) and the other without (GH-LRv3), were tested. Comparison was made with native human GH (growth hormone). GH-LRv2 and GH-LRv3 demonstrated similar pharmacokinetics in rats, showing reduced clearance compared with native GH and potent agonist activity with respect to body weight gain in a hypophysectomized rat model. In M. fascicularis, a low level of antibodies to GH-LRv2 was found in one sample, but there was no other evidence of any immunogenic response to the other fusion protein. There were no toxic effects and specifically no changes in histology at injection sites after two repeated administrations. The pharmacokinetic profiles in monkeys confirmed long half-lives for both GH-LRv2 and GH-LRv3 representing exceptionally delayed clearance over rhGH (recombinant human GH). The results suggest that repeated administration of a GH LR-fusion is safe, non-toxic, and the pharmacokinetic profile suggests that two to three weekly administrations is a potential therapeutic regimen for humans.

Recombinant rat and mouse growth hormones: risk assessment of carcinogenic potential in 2-year bioassays in rats and mice.

Recombinant rat growth hormone (rrGH) and recombinant mouse growth hormone (rmGH) were developed to evaluate the potential carcinogenicity of each biologically active growth hormone (GH) as assessed in the respective species. Biological activities of rrGH and rmGH were demonstrated by showing an increase in body weight gain and serum levels of insulin-like growth factor-1 (IGF-1) in hypophysectomized rats receiving daily sc injections for 6 days. With the exception of pharmacologically mediated weight gain, rrGH and rmGH had no adverse effects in 5-week oral toxicity studies and no production of anti-recombinant GH antibodies. The high doses selected for the carcinogenicity studies provided systemic exposures of GH up to approximately 10-fold over basal levels. In the 105-week mouse carcinogenicity study, daily sc injections of rmGH at 0.1, 0.2, or 0.5 mg/kg/day were well tolerated and had no effects on survival or incidence of tumors. In the 106-week rat carcinogenicity study, daily sc injections of rrGH at 0.2, 0.4, or 0.8 mg/kg/day had a favorable effect on longevity in female rats administered 0.4 or 0.8 mg/kg/day, an increased weight gain in females and males, and no increase in the incidence of tumors. The absence of carcinogenic effects of recombinant GH administered daily for 2 years to rodents was consistent with publications of clinical experience, indicating a lack of convincing evidence for an increased risk of cancer in children receiving human recombinant GH replacement therapy.

Attitudes and behaviors with regards to androgenic anabolic steroids among male adolescents in a county of Sweden.

AIMS: The aim of this study was to investigate attitudes towards androgenic anabolic steroids among male adolescents who have used anabolics compared to those who have not. DESIGN AND SETTING: A cross-sectional survey was performed in the year 2000 in all secondary schools in the county of Halland on the west coast of Sweden. PARTICIPANTS AND MEASUREMENTS: An anonymous multiple-choice questionnaire was distributed to all classes with 14-, 16-, and 18-year-old male adolescents. The response rate was 92.7% (n=4049). FINDINGS: Those who admitted having used androgenic anabolic steroids differed in several ways from those who had not. Fewer believed androgenic anabolic steroids to be harmful [odds ratio (OR) = 0.15, 95% CI 0.08-0.30] and more believed that girls preferred boys with large muscles (OR = 6.1, 95% CI 3.4-11.0). They trained more often at gyms (OR = 5.6, 95% CI 3.0-10.6), drank more alcohol (OR = 4.2, 95% CI 2.0-9.1), and had used narcotic drugs more often (OR = 15.3, 95% CI 8.5-27.5) than the other male adolescents. More immigrants than native-born adolescents had used anabolics (OR = 4.2, 95% CI 2.2-7.9). CONCLUSION: Attitudes towards anabolics differ between users and nonusers. These aspects may be beneficial to focus on as one part of a more complex intervention program in order to change these attitudes and decrease the misuse of androgenic anabolic steroids.

Morphological changes in the kidney of dogs chronically exposed to exogenous growth hormone.

Porcine growth hormone was administered subcutaneously to beagle dogs at doses of 0.025, 0.1, and 1 IU/kg/d for 14 weeks, markedly elevating serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels. This was accompanied by a significant increase in body weight gain and kidney weights in both male and female dogs. The increase in kidney weight (6 to 54%) was slightly greater than the increase in body weight (6 to 40%). By light microscopy, glomerular deposits, mesangial thickening, and very slight cellular infiltration in glomeruli were seen in mid- and high-dose groups. Based on morphometric evaluation, there was an increase in the renal glomerular area, which was statistically significant (p < or = 0.05) in the mid- and high-dose males and in the high-dose females. This was associated with a statistically significant (p < or = 0.05) increase in the number of total glomerular cells in the mid- and high-dose males. By transmission electron microscopy, thickening of the glomerular basal lamina and diffuse increase of the mesangial matrix were observed in both male and female dogs in the mid- and high-dose groups. Immunohistochemical reactions were negative for IgG, IgM, and C3. The morphological changes in the kidney of dogs resemble the diffuse glomerulosclerosis described in human diabetic nephropathy.

Adenoviral vector cytotoxicity depends in part on the transgene encoded.

First-generation adenoviral vectors induce G(2)/M arrest and cell death at high multiplicities of infection (m.o.i.'s) in vitro. It is unclear whether this cytotoxicity is entirely adenoviral gene related or influenced in part by the encoded transgene. We examined this question in epithelial cells using seven vectors at relatively low (50) or higher (200) m.o.i.'s. The vectors contained no transgene (+/-promoter), transgenes encoding a cytoplasmic reporter protein (two luciferase constructs; beta-galactosidase), or transgenes encoding a secretory protein (alpha1-antitrypsin; growth hormone). After 24 h with a m.o.i. of 50, vectors encoding cytoplasmic reporter proteins led to greatest cytotoxicity (approximately 35-40% cells in G(2)/M). Vectors without a transgene resulted in lower cytotoxicity (approximately 15%, minus, or 23%, plus promoter, cells in G(2)/M). Vectors encoding secretory proteins led to approximately 22-25% cells in G(2)/M. A similar pattern resulted when cell number was measured. Results were unrelated to the steady-state levels of transgene product. At the higher m.o.i., all vectors caused substantial growth retardation. This is the first demonstration that adenoviral vector-induced cytotoxic effects are in part related to the transgene encoded.

Evaluation of certain veterinary drug residues in food. Fiftieth report of the joint FAO/WHO Expert Committee on Food Additives.

This report presents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of residues of certain veterinary drugs in food and to recommend maximum levels for such residues. The first part of the report considers the neurotoxicity of anthelminthics belonging to the avermectin and milbemycin classes of compounds and the evaluation policy of the Committee in establishing Maximum Residue Levels (MRLs) for veterinary drugs in food. A summary follows of the Committee's evaluations of toxicological and residue data on a variety of veterinary drugs: five anthelminthic agents (eprinomectin, febantel, fenbendazole, oxfendazole and moxidectin), seven antimicrobial agents (gentamicin, procaine benzylpenicillin, sarafloxacin, spectinomycin, chlortetracycline, oxytetracycline and tetracycline), three antiprotozoal agents (diclazuril, imidocarb and nicarbazin), one glucocorticosteroid (dexamethasone), one production aid (recombinant bovine somatotropins) and one tranquilizing agent (azaperone). Annexed to the report are a summary of the Committee's recommendations on these drugs, including Acceptable Daily Intakes and MRLs, and further toxicological studies and other information required.

Pharmacological and toxicological effects of chronic porcine growth hormone administration in dogs.

The purpose of this study was to evaluate the pharmacological and toxicological effects of exogenous GH administration in normal adult dogs. Because porcine GH (pGH) is structurally identical to canine GH, pGH was selected for a 14-wk study in dogs. Thirty-two dogs (< 2 yr) were randomized to 4 groups (4 dogs/sex/group); 1 group was treated with the vehicle and 3 groups received pGH at 0.025, 0.1, or 1.0 IU/kg/day subcutaneously. Daily clinical signs and weekly body weights were recorded. Hematology, serum biochemistry, urinalyses, electrocardiograms, and ophthalmoscopic examinations were done. Serum GH, insulin-like growth factor-1 (IGF-1), insulin, thyroxine (T4), triiodothyronine (T3), and cortisol levels were determined. Necropsies were performed, organs weighed, and tissues were fixed and processed for light microscopic examination. Porcine GH caused increased body weight gain (p < or = 0.05) through the mid dose; the mean weight gains at study termination in mid- and high-dose groups were 2.8 kg and 4.7 kg, respectively, compared to 0.4 kg and 0.8 kg in control and low-dose groups, respectively. Dose-related increased weights of liver, kidney, thyroid, pituitary gland, skeletal muscle, and adrenal gland were noted. In pGH-treated dogs, increased skin thickness seen grossly correlated histologically with increased dermal collagen. There was no gross or histomorphological evidence of edema. There were dose-related increased serum IGF-1 levels (approximately 2-10-fold; p < or = 0.05) that correlated with the elevated serum GH levels in pGH-treated dogs. Also, increased serum insulin levels (p < or = 0.05) through the mid dose were seen throughout the study. In high-dose dogs, the insulin levels remained elevated over 24 hr postdose. The serum glucose levels in fasted dogs remained within the control range and there was no chronic hyperglycemia based on glycosylated hemoglobin levels. Renal glomerular changes, significant polyuria with decreased urine specific gravity, and increased serum insulin levels suggested that the dogs had early insulin-resistant diabetes. There was minimal or no biologically significant effect of pGH on serum T3, T4, and cortisol levels in dogs. Other serum biochemical changes in pGH-treated dogs included decreased urea nitrogen and creatinine, and increased potassium, cholesterol, and triglycerides. Significant increases in serum calcium and phosphorous levels and alkaline phosphatase activity (bone isozyme) correlated with the histological changes in bone. In pGH-treated dogs, there was a dose-related normochromic, normocytic, nonregenerative anemia. The changes described above, except for the anemia, are related to either anabolic or catabolic effects of high doses of GH. Based on this study, it is concluded that the dog is a good model in which to evaluate the safety of GH secretagogues as well as compounds with GH-like activity.

Morphological changes in the pituitary gland of dogs chronically exposed to exogenous growth hormone.

Growth hormone (GH) synthesis and release from the pituitary is regulated by hypothalamic releasing hormone, insulin-like growth factor-1 (IGF-1), and somatostatin. However, the potential effects of pharmacological doses of exogenous GH on the pituitary are not well studied. To determine the potential chronic effects of exogenous GH on pituitary morphology in dogs, porcine GH (pGH) was administered subcutaneously to 3 groups of dogs (4 animals/sex/group) at doses of 0.025, 0.1, and 1.0 IU/kg/day for 14 wk. A group (4/sex) of dogs served as the vehicle control. The pituitaries from all dogs were weighed and fixed in appropriate fixatives for light and electron microscopic examination; in addition, cells of the pars distalis were quantitated by a point counting method following immunostaining to identify cells containing GH, prolactin (PRL), and adrenocorticotrophic (ACTH) hormones. Administration of pGH resulted in a statistically significant (p < or = 0.05) increased pituitary weight through the high dose. By light microscopy (LM), hypertrophy of pars distalis cells was evident in mid- and high-dose female dogs. The pituitaries of dogs given the lowest dose (0.025 IU/kg/day) of pGH were not remarkable based on weight and LM findings. In addition, transmission electron microscopic (TEM) examination of the pituitary gland of high-dose demonstrated, in both sexes, pituitary cells with variably dilated rough endoplasmic reticulum and decreased numbers of secretory granules; some of these cells reacted positively to GH immunostaining. Quantitative analysis of the pituitary gland of high-dose males and females showed an increase in the absolute volume of all cell populations studied: GH-, PRL-, and ACTH-positive cells. Based on the LM and TEM findings, the increased volume of the cell populations studied is likely related to cellular hypertrophy. The expected elevation in serum GH levels following repeated administration of pGH and an associated elevation in serum IGF-1 levels resulted in morphologic changes in the pituitary gland of dogs given high doses (> or = 0.1 IU/kg/day) of pGH; these observations differed from the reported findings in pituitaries of transgenic mice secreting large quantities of bovine GH.

Effect of chronic growth hormone administration on skeletal muscle in dogs.

Administration of growth hormone (GH) results in increased body weight gain in dogs. Increased body weight gain is believed to be a result of the trophic effect of GH on the musculoskeletal system. However, edema is one of the side effects described in man following exogenous GH administration. Thus, the objective of this study was to determine if the expected increased weight gain in GH-treated dogs is a result of increased muscle mass. Porcine growth hormone (pGH), administered subcutaneously to beagle dogs at doses of 0.025, 0.1, and 1 IU/kg/day for 14 wk, resulted in elevated serum GH and insulin-like growth factor-1 (IGF-1) levels (see accompanying paper, Prahalada et al). This was associated with a significant increase in body weight gain and weights of the cranial tibialis muscle in both male and female dogs. The increased muscle mass likely contributed to the significant increase in body weight gain seen in both sexes. Quantitative analysis of skeletal muscle sections stained for ATPase activity showed increases in type I (slow twitch) and type II (fast twitch) myofiber sizes in mid- and high-dose males and in high-dose females. The ratio of type I and type II muscle fibers remained unchanged. Hypertrophic myofibers were enlarged but had a normal histologic and ultrastructural organization when observed by light and transmission electron microscopy. The results of this study have demonstrated that increased muscle mass in pGH-treated dogs is related to hypertrophy of muscle fibers and not due to edema. Exogenous GH administration has an anabolic effect on skeletal muscle in dogs.

Unwanted effects of growth hormone excess in the adult.

This review discusses in vitro, animal and human studies which provide insights into the deleterious effects of excess GH and IGF-I. The systemic sequelae of hypersomatotrophism include disorders of the cardiovascular, respiratory and rheumatologic systems. Impaired carbohydrate metabolism and an increased incidence of gastrointestinal malignancy also contribute to morbidity and an average 10 year reduction in mortality. Major determinants of these sequelae appear to include both the magnitude and duration of hypersomatotrophism. Extrapolation of these findings to adults receiving replacement or pharmacologic doses of GH requires longer term controlled studies.

Growth hormone treatment and development of malignancy: recombinant human growth hormone does not induce leukemia in AKR/O-mice.

In 1988 several reports described leukemia in former/present growth hormone (GH)-treated children, and a doubled incidence of leukemia in GH-treated children was concluded in a workshop in Bethesda. A mouse strain (AKR/O) with a high incidence of leukemia was used as a model. AKR/O-mice in the preleukemic adult age and younger mice during rapid growth were treated with recombinant human GH (rhGH) in human therapeutic doses to see whether this treatment would affect the time and presentation of malignant disease. The malignant development did not appear earlier or in a different way in the animals receiving rhGH from day 6 to 50 than in their appropriate controls. A borderline protective effect to the development of leukemia was seen in the adult group receiving rhGH; in this group antibodies to hGH also developed. We conclude that in this experimental model human therapeutic doses of rhGH do not influence the development of malignancy in the AKR/O mice.

Recombinant human growth hormone promotes human lymphocyte engraftment in immunodeficient mice and results in an increased incidence of human Epstein Barr virus-induced B-cell lymphoma.

Recombinant human growth hormone (rhGH) previously has been demonstrated to promote human or mouse T-cell engraftment in immunodeficient mice. We then wanted to examine long-term effects of rhGH on human cell engraftment in these mice. Mice with severe combined immune deficiency (SCID) were given human peripheral blood lymphocytes or human bone marrow cells and daily injections of rhGH (20 micrograms ip every other day). Upon later assessment for engraftment by flow cytometric analysis, it was determined that rhGH strongly promoted human T-cell engraftment in the thymus and spleens of these mice. However, there was considerable variability in both the incidence and extent of engraftment which appears to be due to donor-to-donor variation. Additionally, rhGH promoted B lymphomagenesis in these mice since long-term treatment of these xenogeneic chimeras with rhGH resulted in the increased incidence of human Epstein-Barr virus (EBV)-infected B-cell lymphoma. Thus, while rhGH can be used to optimize human T-cell engraftment in SCID mice, it also increases the likelihood of B-cell lymphoma generation when the donor is EBV infected. The results suggest that the activation of human T cells by rhGH results in an increased ability of these cells to traffic to the peripheral lymphoid organs of the SCID mice and results in a lymphoid microenvironment conducive to the outgrowth of EBV-transformed B lymphocytes.

Endocrine manipulation--toxicological frontiers.

A variety of hormonal products has been developed for use in food animal production. Applications include therapy, particularly for fertility problems, zootechnical purposes comprising mainly the management of reproduction, for example the synchronization of oestrus, and the improvement of performance such as increased growth rate or increased milk yield. Although there is well established legislation both domestically and internationally for the registration of veterinary pharmaceutical products, hormones have become a special case at least to the public. This is particularly true when hormones are used to improve animal performance. The two notable issues to date have been the use of anabolic steroids as growth promoters and of bovine somatotrophin (BST) to increase milk yield in dairy cows. The high public profiles of these two issues have separately forced the introduction of new legislation in the EC, which will continue to have far-reaching implications for research and development in animal health and production for many years. This paper interprets recent developments in legislation concerning veterinary products and hormonal products in particular, giving examples of the toxicological assessment of four specific molecules and speculating upon the likely implications for the future practical exploitation of endocrine mechanisms in food animal production.

Stimulatory effects of growth hormone on rat bladder carcinogenesis.

The authors investigated the influences of recombinant human growth hormone (rh-GH) on rat urinary bladder carcinogenesis induced with N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Rats belonging to the control group (Group I, n = 19) were given 0.05% BBN in drinking water for 9 weeks, and the bladder was excised on the 22nd week after the initiation of BBN administration and inspected. All animals developed visible tumors in the bladder. The mean number of tumors per bladder was 11.26 +/- 5.21, and the mean total volume of tumors per bladder was 126.1 +/- 212.7 microliters. In all but one of the experimental groups (Group V) and in the control group, all animals developed visible tumors in the bladder. When 0.5 units of rh-GH was injected subcutaneously once a week from the week 1 through the week 6 (Group II; n = 20), the mean number of tumors and mean total volume of the tumors were 12.15 +/- 6.59 and 206.6 +/- 318.0 microliters, respectively. When the administration period of rh-GH was changed to between week 7 through the week 12 (Group III; n = 19), the mean number of tumors and mean total volume of the tumors were 16.95 +/- 7.07 and 204.5 +/- 317.7 microliters, respectively. When rh-GH was administered from the week 13 through the week 18 (Group IV; n = 19), the respective values were 16.79 +/- 10.75 and 213.4 +/- 274.6 microliters. In Group V (n = 19), which received only rh-GH from week 1 through the week 6, no tumors were detected. There were statistically significant differences in the mean tumor numbers between Groups I and III, Groups I and IV, and Groups II and III. The mean volume of individual tumor was the greatest in Group II, although the differences were not statistically significant in comparison with the other groups. Histologically, all tumors were transitional cell carcinoma in every group. There were no statistically significant differences in distributions of tumor stage and tumor grade between any groups. These findings suggest that rh-GH enhances the promotion of carcinogenesis of chemically induced rat urinary bladder cancer. It will be necessary to elucidate whether this effect of rh-GH is expressed by the somatostatin hypothesis of GH action, its direct action, or some other mechanisms.

Recombinant porcine somatotropin: an immunotoxicology study.

The present study was designed to determine the effect of recombinant porcine somatotropin (rpST; 5, 15, or 25 mg.pig-1.d-1 for 57 d) on a variety of immune function variables. We observed no significant effect of rpST treatment on the gross pathology of the pigs, histopathology of the immune system organs, total and differential white blood cell counts, lymphocyte blastogenic response to mitogens, or the neutrophil functions of chemotaxis, ingestion, reduction of cytochrome C, iodination, and antibody-dependent cell-mediated cytotoxicity. Those variables that were significantly affected by rpST treatment include a decreased hemoglobin and packed red blood cell volume (at some time points for all three rpST dosages), a decrease in plasma protein level at the 25-mg dose, a small increase in neutrophil random migration (at all three rpST dosages), and a decrease in IgG antibody response to tetanus toxoid at 15 d after immunization (but not at d 8, 22, or 29). Additionally, rpST treatment was associated with a decreased rate of BW gain (at 15-mg dose), increased liver and kidney weights (at all three dosage levels), and an increased incidence of renal tubular cytoplasmic vacuolation of minor severity. There were no observed differences in the overall health of the pigs due to rpST treatment, based on clinical observations as well as determination of antibody titer to, and isolation of, common swine pathogens. Therefore, there was no evidence that the observed influence of rpST treatment on immune function would be clinically relevant.

A recombinant-DNA-derived modification of human growth hormone (hGH44-191) with enhanced diabetogenic activity.

A modified human growth hormone (hGH) that lacks the first 43 residues of the intact hormone was prepared by recombinant-DNA technology. For preparative purposes an additional alanine was made the amino terminal residue. Sequence analysis and tryptic peptide mapping combined with amino acid analyses confirmed the structure of the polypeptide. Less than 2% N-terminal methionine was detected. The hGH44-191 was estimated to be at least 10 times more active than hGH in producing glucose intolerance in obese yellow mice (Avy/A) and was equipotent to hGH in increasing serum free fatty acids in fasted, hypophysectomized rats. The peptide did not promote growth in hypophysectomized rats nor did it exhibit early (1h) insulin-like activity in fasted, hypophysectomized rats, as indicated by its failure to lower blood glucose and fatty acids. The modified hGH was inactive in the Nb-2 cell assay but was about one-third as active as hGH in stimulating the pigeon crop sac. In radioimmunoassays using 125I-labeled hGH and polyclonal antibodies to intact hGH, cross-reactivity of hGH44-191 was less than 1%. We conclude that removal of the amino terminal portion of hGH enhances its diabetogenic properties, and that this activity does not depend upon the ability to promote growth. Furthermore, the insulin-like activity can be separated from its diabetogenic action by deletion of the first 43 amino terminal residues. This is the first report of a modified hGH that has anti-insulin effects greater than hGH itself.