Clinical mastitis in cows treated with sometribove (recombinant bovine somatotropin) and its relationship to milk yield

Effect of sometribove (methionyl bovine somatotropin) on mastitis in 15 full lactation trials (914 cows) in Europe and the US and 70 short-term studies (2697 cows) in eight countries was investigated. In full lactation studies, sometribove (500 mg/2 wk) was given for 252 d, commencing 60 d postpartum. Although herds varied considerably, incidence of clinical mastitis within a herd was similar for cows receiving control and sometribove treatments. Relative risk analyses indicated no treatment effect, and percentage of mastitis during treatment was similar for control and sometribove groups. A positive linear relationship existed between peak milk yield and mastitis incidence (percentage of cows contracting mastitis or cases per 100 cow days); sometribove treatment did not alter this relationship. Increases in mastitis related to milk yield increase from sometribove or related to genetic selection were similar. When expressed per unit of milk, mastitis incidence declined slightly as milk yield increased; this relationship was not altered by sometribove. No effect on clinical mastitis was observed in 70 commercial herds utilizing sometribove for 84 d. However, effects were significant for stage of lactation and milk yield. Overall, studies represented a wide range of research and commercial situations demonstrating that sometribove had no effect on incidence of clinical mastitis during the lactation of treatment. Furthermore, sometribove did not alter typical relationships between milk yield or herd factors and incidence of clinical mastitis.

Effect of daily replacement therapy with recombinant bovine somatotropin on somatotropin, insulin-like growth factor I, and onset of puberty in beef heifers immunized against growth hormone-releasing factor

Two experiments examined whether replacement therapy with recombinantly derived bovine somatotropin (rbST) would induce puberty in heifers that had been actively immunized at 6 mo of age against growth hormone-releasing factor (GRF). Heifers received daily i.m. injections of 25 mg of rbST (Exp. 1, n = 6; Exp. 2, n = 4) or vehicle (VEH; Exp. 1, n = 6; Exp. 2, n = 4) for 56 d. Serum concentrations of somatotropin (ST, nanograms/milliter) were low in all heifers before first injection in Exp. 1 (1.56 +/- .04) and 2 (.95 +/- .03). During treatment, serum ST was greater (P < .01) in rbST than in VEH heifers (75.4 +/- 4.8 vs 2.8 +/- .1 ng/mL, respectively) in both experiments and remained increased through d 57 (32.2 +/- 6.4 vs .90 +/- .01 ng/mL). IN Exp. 1 and 2, concentrations of serum IGF-I were similar in rbST and VEH heifers before treatment, increased (P < .01) 12 h after first rbST, and remained increased (P < .01) through d 57 in rbST heifers. Concentrations of serum insulin (INS) and plasma glucose (GLU) were similar (P > .10) in rbST and VEH heifers before first injection (Exp. 1 and 2). Serum INS (micro-units/milliliter) was greater (P < .01) in rbST (61.7 +/- 3.7 and 36.0 +/- 2.4) than in VEH (12.4 +/- 1.6 and 8.1 +/- 1.0) heifers on d 1 or 2 only, in Exp. 1 and 2, respectively. In Exp. 1, GLU was increased (P < .05) by rbST on d 2 through 57, but only on d 1 in Exp. 2. Proportion of heifers pubertal by d 21 tended to be greater (P < .07) in rbST (3 of 6) than in VEH (0 of 5) heifers in Exp. 1, but not in Exp. 2 (1 of 4 vs 1 of 4, respectively). All heifers in Exp. 1 and 50% of the heifers in Exp. 2 attained puberty by d 56. Daily rbST increased ST, IGF-I, INS, and GLU but did not hasten onset of puberty in heifers immunized against GRF.

Recombinant human growth hormone accelerates wound healing in children with large cutaneous burns

OBJECTIVE

Two forms of recombinant growth hormone that accelerate the healing of skin graft donor sites in severely burned children were evaluated.

SUMMARY BACKGROUND DATA

Growth hormone has been shown to reduce wound healing times in burned pediatric patients. Through genetic engineering, several different forms have been synthesized; however, not all are marketed currently. Two forms of growth hormone were used in these studies, Protropin (Genentech, Inc., San Francisco, CA), a commercially available product that possesses a N-terminal methionine residue not found in the second form Nutropin (Genentech, Inc., San Francisco, CA), which, as yet, is not commercially available. Through the use of recombinant human growth hormone, rapid wound healing may reduce the hypermetabolic period, the risk of infection, and accelerate the healing of donor sites used for grafting onto burned areas. The two structurally different forms of growth hormone were tested for their efficacy in healing donor sites in severely burned children.

METHODS

Forty-six children, with a > 40% total body surface area and > 20% total body surface area full-thickness burn were entered in a double-blind, randomized study to receive rhGH within 8 days of injury. Twenty received (0.2 mg/kg/day) Nutropin or placebo by subcutaneous or intramuscular injection beginning on the morning of the initial excision. Eighteen patients who failed the entry criteria for receiving Nutropin received Protropin therapeutically (0.2 mg/kg/day). Donor sites were harvested at 0.006 to 0.010 inches in depth and dressed with Scarlet Red impregnated fine mesh gauze (Sherwood Medical, St. Louis, MO). The initial donor site healing time, in days, was reached when the gauze could be removed without any trauma to the healed site.

RESULTS

Donor sites in patients receiving Nutropin (n = 20) or Protropin (n = 18) healed at 6.8 +/- 1.5 and 6.0 +/- 1.5 (mean +/- SD) days, respectively, whereas those receiving placebo (n = 26) had a first donor site healing time of 8.5 +/- 2.3 days. Both groups receiving rhGH showed a significant reduction in donor site healing time compared with placebo at p < 0.01. When subgroups were compared, no difference in healing times could be shown with regards to age or time of admission after injury.

CONCLUSION

Our results indicate that both forms of rhGH are effective in reducing donor site healing time compared with placebo and suggest that accelerating wound healing is of clinical benefit because the patients' own skin becomes rapidly available for harvest and autografting. With this increase in the rate of wound healing, the total length of hospital stay can be reduced by more than 25%.

Growth hormone (GH) binding and effects of GH analogs in transgenic mice

Overexpression of human (h) or bovine (b) growth hormone (GH) in transgenic mice is associated with marked (2- to 12-fold) and significant increase in hepatic binding of GH and prolactin (PRL). This is due to an increase in the number of GH and PRL receptors (GHR, PRLR) per mg of microsomal protein without changes in binding affinity. Comparison of results obtained in transgenic animals expressing bGH with a mouse metallothionein (MT) or a rat phosphoenolpyruvate carboxykinase (PEPCK) promoter suggests that effects of bGH on hepatic GHR and PRLR do not require GH overexpression during fetal life and, within the dose range tested, the effects on PRLR are not dose dependent. The increase in hepatic GHR was accompanied by significant increases in plasma GH-binding protein (GHBP) and in mean residence time of injected GH. Thus, life-long elevation of peripheral GH levels alters the availability of both free GH and GHR. Site-directed in vitro mutagenesis was used to produce hGH and bGH analogs mutated within one of the sites involved in binding to GHR and PRLR. Mutating hGH to produce amino acid identity with bGH at Position 11, 18 (within Helix 1), 57, or 60 (within the loop between Helix 1 and 2) did not affect binding to GHR in vitro, or somatotropic activity in transgenic mice in vivo but reduced lactogenic activity in Nb2 cells by 22%-45%. Mutations of bGH designed to produce amino acid identity with hGH at one to four of the corresponding positions in the bGH molecule did not interfere with binding to GHR or somatotropic activity in vivo, and failed to produce significant binding to PRLR but resulted in alterations in the effects on the hypothalamic and anterior pituitary function in transgenic mice. Apparently region(s) outside the domains examined are essential for lactogenic activity of hGH, and different portions of the GH molecule are responsible for its diverse actions in vivo.

In vitro and in vivo studies of antagonistic effects of human growth hormone analogs

A bovine growth hormone (bGH) analog, bGH-G119R, has been shown to act as a functional antagonist of GH activity both in vitro and in vivo. In the present study, human (h) GH analogs with alterations in the third alpha-helix (G120A, G120R) and N terminus (I4A) were generated. These two regions have been reported to form binding site 2 in hGH, which is involved in in vitro dimerization of the GH receptor (GHR). The biological activities of these hGH analogs were tested in vitro by a radioreceptor assay and an assay to test the ability of the molecules to induce tyrosine phosphorylation of a 93-kDa protein in a human lymphocyte line, IM-9. The growth rate of transgenic mice that express different hGH analogs was used as an in vivo test of the activity of the molecules. The results demonstrated that G120R is a potent hGH antagonist both in vitro and in vivo. Transgenic mice expressing G120R demonstrated a growth-suppressed phenotype. However, I4A, which has been demonstrated to be a potent inhibitor of in vitro GHR dimerization, exhibited full growth promoting activity in transgenic mice. Thus, the ability of hGH analogs to induce GHR dimerization in vitro and the ability to promote growth in vivo are not directly correlated.

Pharmacological characterization of a biosynthetic trisulfide-containing hydrophobic derivative of human growth hormone: comparison with standard 22 K growth hormone

Growth hormone is the classical anabolic hormone which promotes organ growth after binding to somatogenic target cell receptors, present in various target tissues. The present study elucidated the pharmacological characteristics in vitro and in vivo of human growth hormone and a recently identified by-product of a recombinant human growth hormone preparation; i.e. a trisulfide-containing (cys 182-cys 189) hydrophobic, folding derivative of growth hormone, hydrophobic derivative-growth hormone. Standard growth hormone and hydrophobic derivative-growth hormone possessed similar characteristics in vitro, both as regards binding to the somatogenic receptor on the human IM-9 cell line, and the prolactin receptor-mediated proliferation of rat Nb2 cells. This indicates that no change occurs in the binding characteristics in spite of a change in conformation of the molecule. Using an ELISA assay that detected standard and hydrophobic derivative-growth hormone equally well, the plasma pharmacokinetical profiles of the preparations following a single intravenous or subcutaneous dose were indistinguishable. Thus, following initial disposition of hydrophobic derivative-growth hormone and standard growth hormone into a volume, V1, of one to two times the plasma volume, almost 90% of either compound disappeared from plasma during the alpha-phase of the plasma decay curve. Similar half-lives of 4-5 min. were found for hydrophobic derivative-growth hormone and standard growth hormone during this phase, indicating rapid removal of drug from the circulation. Also, the AUC and Cmax values for standard and hydrophobic derivative-growth hormone did not differ following intravenous or subcutaneous administration.(ABSTRACT TRUNCATED AT 250 WORDS)

[Analysis of the relationship between the effect of growth hormone therapy and the width of the radial metaphysis]

A radio-dense metaphyseal band (MB) of different width is present at the distal end of the radius in growing children. Authors studied 30 prepubertal children before and after one and two years of treatment by recombinant human growth hormone (rhGH). They examined the relationship between the MB, bone age (BA), height velocity (HV) and insulin like growth factor-I (IGF-I). However all the four parameters showed significant change in the study period, correlation was found only after the second year of treatment between the change MB and IGF-I levels. Authors suggest that the regulation of bone growth in these children can be compared only after two years to the normally growing children.

A novel 3-substituted benzazepinone growth hormone secretagogue (L-692,429)

The 3-substituted benzazepinone, L-692,429 (compound 1), is the prototype compound of a novel class of compounds that stimulate release of growth hormone (GH). The molecule evolved from efforts to identify a non-peptide mimic of the growth hormone-releasing hexapeptide, GHRP-6. Compound 1 is prepared by sequential attachment of dimethyl-beta-alanine and 2'-biphenylyltetrazole side chains to a chiral 3-aminobenzolactam nucleus. Comparison of the biological activity of 1 with the corresponding six- and eight-membered lactam analogs shows the seven-membered benzazepinone skeleton to be preferred. Molecular modeling of the structurally diverse GH secretagogues, L-692,429 and GHRP-6, was performed.

Pioglitazone inhibits the diabetogenic action of growth hormone, but not its ability to promote growth

Analogs of thiazolidinedione improve the responsiveness of insulin-resistant animals to insulin. One such analog, pioglitazone (5-(4-[2-(5-ethyl-2-pyridinyl)ethoxy]benzyl)thiazolidine-2,4-dione hydrochloride), when fed to insulin-resistant animals such as the obese (ob/ob) mouse, reduces blood glucose and lipids and also lowers the plasma insulin level. Because GH can produce insulin resistance in humans and animals such as the ob/ob mouse, the present study was conducted to determine whether feeding pioglitazone can 1) inhibit the ability of GH to induce enhanced insulin resistance in obese mice, 2) ameliorate or reverse GH-induced insulin resistance once it has been induced in ob/ob mice, and 3) alter the ability of GH to promote growth in hypophysectomized rats. Female ob/ob mice were fed a control diet or a diet containing pioglitazone (20 mg/kg animal.day) for 4 days. During the last 3 days of the feeding period, the mice also received a daily sc injection of either saline or 200 micrograms S-carboxymethylated human GH (RCM-hGH), which is a GH derivative having mainly diabetogenic activity. In control-fed mice, RCM-hGH increased blood glucose and plasma insulin levels, which is an expected response to GH-induced insulin resistance. By contrast, the ability of RCM-hGH to increase blood glucose and plasma insulin levels was totally blocked in pioglitazone-fed mice. To determine whether pioglitazone can ameliorate GH-induced insulin resistance once it has been established, ob/ob mice were treated sc with either saline or 200 micrograms RCM-hGH for 3 days. Half of the saline-treated and half of the hormone-treated mice were then fed pioglitazone, whereas the remaining animals were continued on the control diet. After 48 h on the diets, the blood glucose and plasma insulin levels of the RCM-hGH treated mice fed the control diet remained elevated with respect to those in the saline-treated controls. On the other hand, the blood glucose and plasma insulin levels of the RCM-hGH treated mice fed pioglitazone were markedly reduced compared to those of the RCM-hGH-treated control-fed animals. Thus, these results suggest that pioglitazone can ameliorate GH-induced insulin resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterisation of a trisulphide derivative of biosynthetic human growth hormone produced in Escherichia coli

A novel protein derivative has been found during process development of biosynthetic human growth hormone; it has been characterised as human growth hormone with a Cys182-Cys189 trisulphide bridge. We have not been able to find a previous report in the literature about this kind of derivative. The characterisation was obtained partly on the full-length derivative and partly on a tryptic fragment of the derivative. The full-length derivative was characterised by reduction with 1,4-dithiothreitol followed by electrospray mass spectrometry, treatment with cysteine and measurement of hydrogen sulphide liberation upon cysteine treatment. The tryptic fragment from peptide mapping was characterised by amino acid analysis, amino acid sequencing and mass spectrometry. All data indicated an extra sulphur atom in the Cys182-Cys189 cystine bridge.

Five years experience with recombinant human growth hormone treatment of children with chronic renal failure

11 males, aged 2.5-16.3 years (6.8 +/- 4.1) with growth retardation (Standard Deviation Score--SDS > -2.00) consequent to chronic renal failure (CRF) received recombinant human growth hormone (rhGH) for 18 to 60 mo (40.9 +/- 15.4). Growth velocity (GV) increased from 5.4 +/- 2.2 for the year prior to rhGH to 8.9 +/- 1.6 (p = 0.00001), 7.4 +/- 1.7 (p < 0.03), 7.6 +/- 1.6 (p < 0.006), 6.5 +/- 1.0 (p < 0.05) and 7.5 +/- 1.3 (p = NS) cm/yr following 12, 24, 36, 48 and 60 mo respectively of treatment. The mean SDS for height decreased from -3.21 at baseline to -0.85 at 60 mo (p = 0.0004); 7 of 8 pts treated for > 36 mo had a SDS more positive than -2.00; 3 reached the 50th percentile on the growth curve. In 2 patients the dosage was doubled to achieve the increase in GV; in one patient it took 5 yrs to reach a SDS more positive than -2.00. A significant increase in weight gain and mid-arm muscle circumference over baseline values were indicative of the anabolic effect of rhGH. The mean increase in bone age was similar to the increase in chronologic age; the delta bone age-delta height age was not significant indicating no loss of growth potential following rhGH. Although 3 patients required the initiation of dialysis following rhGH treatment, the mean calculated creatinine clearance did not decrease significantly. No significant adverse effects were noted. These data indicate that long-term rhGH treatment is effective in improving the GV of children with CRF and facilitating catch-up growth without loss of growth potential.

Site-directed mutagenesis of hGH at the 54-74 loop selectively modifies its lactogenic receptor-mediated biological activity

Four analogues of human growth hormone (hGH) mutated by site-directed mutagenesis at the 54-74 loop-Met-hGH(P59A), Met-hGH(P61A), Met-hGH(P59A,P61A) and Met-hGH(Des 62-67) were analyzed for: (1) their biological activity mediated through lactogenic receptors using rat lymphoma Nb2-11C cell proliferation and mouse mammary gland HC-11 cell beta-casein synthesis bioassays and (2) their ability to interact with recombinant hGH binding protein (hGHBP). The analogues Met-hGH(P59A), Met-hGH(P61A) and Met-hGH(P59A,P61A) partially lost their activity relative to native hGH in the HC-11, but not in the Nb2-11C cell bioassay. These analogues were nevertheless capable of forming a 1:2 complex with a recombinant hGH binding protein (hGHBP), despite the fact that the affinity of Met-hGH(P61A) and Met-hGH(P59A,P61A) analogues had decreased 8- and 14-fold, respectively. Met-hGH(Des 62-67) failed to form 1:1 or 1:2 complexes with hGHBP and did not compete with [125I]hGH for binding to hGHBP. It lost all biological activity in HC-11 cells, but retained 0.4% of its activity, in the Nb2-11C cell proliferation bioassay. These results confirm the involvement of Pro-61 in the hGH binding and activity mediated through somatogenic receptors, while the activity mediated through two different types of lactogenic receptors was selectively modified. These findings emphasize the fact that lactogen receptors in different species or organs are not identical.

Growth hormone attenuates Na(+)-dependent hepatic amino acid transport in endotoxemic rats

The effects of human growth hormone (GH) on hepatic Na(+)-dependent amino acid transport were studied in endotoxin-treated rats. Adult rats received GH (6 mg/kg BW subQ q 12 hours x 4 doses) or vehicle prior to a single dose of Escherichia coli endotoxin (LPS, 7.5 mg/kg BW IP). Four hours after LPS administration, livers were excised and hepatocyte plasma membrane vesicles (HPMVs) were prepared by differential and Percoll density gradient centrifugation. Hepatocyte plasma membrane vesicle transport of [3H]-MeAIB, a highly selective system A substrate, [3H]-glutamine, a selective system N substrate, and [35S]-cysteine, a system ASC substrate, were measured by a rapid mixing/filtration technique. Vesicle purity and functionality were assessed by marker enzyme measurements and classic overshoots and timecourses that showed similar vesicle size. Endotoxin treatment resulted in a two-fold increase in the activities of systems N and ASC, which was the result of an increase in carrier Vmax (Km was unchanged), and a four-fold stimulation of system A. Pre-treatment with GH diminished the endotoxin-induced increase in Na(+)-dependent amino acid transport by 60%-80%; this reduction in carrier-mediated transport activity was a result of a decrease in Vmax, consistent with a decrease in the number of functional transporter proteins in the plasma membrane. Growth hormone treatment attenuates the endotoxin-induced increase in the activities of the major Na(+)-dependent transporters in rat liver. This may diminish hepatic ureagenesis and spare amino acids for peripheral protein synthesis and thereby explain, at least in part, the ability of growth hormone to promote positive nitrogen balance in catabolic states.

Heterologous humoral immune response in patients treated with human growth hormone from different sources

The existence of homologous anti-human growth hormone (anti-hGH) and heterologous anti-bovine growth hormone (anti-bGH) humoral immune responses in hypopituitary patients under hGH therapy has been reported previously. In order to study the influence of the hormone source, both responses were compared by radiobinding assays performed with [125I]hGH or [125I]bGH as tracers. Fifty-seven hypopituitary patients treated with extractive hGH, recombinant methionyl hGH or authentic recombinant hGH were studied. A very low incidence of heterologous antibodies was found in patients under recombinant hGH therapy, contrary to the high incidence observed in patients treated with extractive hGH preparations. In addition, immunochemical studies performed with a synthetic peptide (hGH 44-128) indicated that this peptide exhibited, in the anti-bGH/[125]bGH radioimmunoassay system, higher reactivity than the native hGH, suggesting that such a fragment resembled an altered conformation of the hormone. The high heterologous response elicited only by the extractive hGH along with the behaviour of the hGH 44-128 fragment supports the fact that the extraction and purification procedures in extractive preparations may alter slightly the structure of the hGH molecule and trigger a heterologous immune response.

A growth hormone (GH) analog that antagonizes the lipolytic effect but retains full insulin-like (antilipolytic) activity of GH

An analog of bovine growth hormone (bGH-M8: [Leu117, Arg119, Asp122]-bGH) with an idealized amphiphilic third alpha-helix has been proposed to be a functional antagonist of GH. In accordance with this proposition, bGH-M8 profoundly inhibited bGH-stimulated lipolysis by chicken adipose tissue in vitro. bGH-M8 alone was a weak agonist in the lipolytic assay (1.9% the potency of bGH). The present evidence indicates that bGH-M8 is a competitive antagonist of the lipolytic action of GH based upon the following results: (i) increasing concentrations of bGH-M8 (antagonist) produce progressively greater inhibition of GH-stimulated lipolysis; (ii) increasing concentrations of bGH (agonist) are capable of overcoming this antagonism; and (iii) Schild plot analysis (slope = -0.94) suggests a receptor antagonist with an equilibrium dissociation constant (KB) of 4.54 nM. In contrast to the antagonistic effects of bGH-M8 on bGH-stimulated lipolysis, bGH-M8 retained full insulin-like ("antilipolytic") activity (i.e., inhibition of glucagon-induced lipolysis). bGH-M8 and bGH were similarly potent in eliciting antilipolytic effects in vitro. Moreover, the antilipolytic effects of bGH-M8 and bGH were additive. Therefore, the third alpha-helix (particularly residues 117, 119, and 122) of bGH contains major structural determinants for the lipolytic effects of GH. The ability of bGH-M8 to act as an antagonist for at least one action of GH (lipolysis) while being a full agonist for another (antilipolysis) suggests that different domains of GH are responsible for its various biologic activities, possibly involving different binding sites and/or signal transduction mechanisms.

Recombinant growth hormone treatment of amyotrophic lateral sclerosis

Based on the known trophic effects of growth hormone (GH) on nerve and muscle 75 patients with ALS were treated for up to 18 months with synthetic human growth hormone (Protropin) or a placebo. The course of ALS was assessed serially using a quantitative (TQNE) neuromuscular and manual exam (MRC) and laboratory chemistries. Average insulin-related growth factor (IGF-I) values increased from 1.2 to 2.3 U/mL in the treated group. Surprisingly, serum insulin levels did not increase. Hyperglycemia was noted in only 2 patients of the 38 patients receiving hGH, and this resolved with cessation of treatment. Over the 12 months of treatment there were 11 deaths (6 controls, 5 treated). Survival analysis, performed approximately 12 months following cessation of treatment, did not reveal a difference between the treatment and placebo group. The TQNE scores declined inexorably in both the control and treated group. Retrospective analysis of the TQNE data indicated a poor prognosis for patients who lost arm strength early. A correlation between the TQNE and MRC scores was evident at early stages of motor unit loss, less so when muscle weakness was advanced.

Influence of recombinant bovine somatotropin (sometribove) on mononuclear cells during the nonlactating period

Recombinant bST was evaluated as a potential immunoenhancer of bovine peripheral blood and mammary gland mononuclear cells during the nonlactating period. Cows (n = 4 per group) were assigned to one of four treatments: 1) untreated, 2) treated with recombinant bST during lactation only, 3) treated with recombinant bST during the nonlactating period only, and 4) treated with recombinant bST during lactation and the nonlactating period. Recombinant bST treatment during the nonlactating period had no effect on proliferation of bovine blood or mammary gland mononuclear cells in response to stimulation by mitogens or allogeneic cells. Recombinant bST treatment during the nonlactating period enhanced interleukin-2 secretion by mononuclear cells isolated from cows treated also with recombinant bST during lactation. However, recombinant bST treatment during the nonlactating period had little effect on interleukin-2 secretion by mononuclear cells from cows not treated with recombinant bST during lactation. Results of this study suggest that recombinant bST alters effector functions rather than proliferation of bovine mononuclear cells.

The stimulatory effect of insulin on diacylglycerol generation in adipocyte membranes from ob/ob mice is impaired by growth hormone

Physiologically, the action of insulin on carbohydrate and lipid metabolism is opposed by several hormones, including glucocorticoids, glucagon, catecholamines, and pituitary GH. Perhaps least is known about the mechanism(s) involved in the antiinsulin action of GH. Since the generation of diacylglycerol (DAG) appears to be an early event in the insulin-signaling cascade, it was of interest to determine whether GH would interfere with this effect of insulin. Experiments were conducted to determine whether insulin would stimulate the generation of DAG in adipocytes of the obese (ob/ob) mouse, and whether this response could be blocked by the diabetogenic GH derivative S-carboxymethylated human GH (RCM-hGH). Isolated adipocytes of the ob/ob mouse were used for these studies, because unlike normal rodents, the ob/ob mouse responds predictably to the antiinsulin action of GH. Insulin produced a rapid biphasic increase in the amount of DAG in a crude membrane fraction of the adipocytes. The first peak in DAG mass occurred within 5 min of exposure of the cells to insulin, and the second peak occurred after 30 min. The first peak in DAG mass did not occur in adipocytes that had been incubated with pertussis toxin before exposure to insulin. Also, adipocytes isolated from ob/ob mice that had been treated with RCM-hGH failed to respond to insulin with an increase in DAG mass. RCM-hGH blocked both the first and second insulin-induced peaks in DAG mass within 6 h of its administration. This is the time at which ob/ob mouse adipocytes exhibit increased insulin resistance in response to RCM-hGH. Neither exposure to insulin nor treatment with RCM-hGH had any appreciable effect on the fatty acid composition of the DAG present in the adipocyte membranes. These findings are compatible with the idea that GH produces some defect in the insulin-signaling cascade that is proximal to the events that result in the generation of DAG in the adipocyte.

Effects of recombinant bovine somatotropin (sometribove) on ovarian function in lactating and nonlactating dairy cows

Metabolic and ovarian responses of lactating and nonlactating cows to recombinant bST (sometribove) were measured. Eighteen lactating cows (60 to 100 d postpartum) and 6 nonlactating cows (> 400 d postpartum) were injected daily with bST or saline during one of two periods. Concentrations of hormones and metabolites were measured in plasma, and ultrasonography was used to quantify ovarian follicular growth. Concentrations of glucose, insulin, IGF-I, progesterone, and estradiol in plasma were greater in nonlactating cows than in lactating cows. Lactating cows had fewer class 2 (6- to 9-mm) and class 3 (10- to 15-mm) follicles and more class 4 (> 15-mm) follicles than nonlactating cows. Bovine somatotropin increased the numbers of follicles in lactating cows so that the numbers of class 2 and of class 3 follicles were equivalent to those for non-lactating cows. Sizes of the largest follicles were similar for bST-and saline-treated cows. The second largest ovarian follicles, however, were larger in bST-treated cows. Ovarian follicular dynamics were altered by bST and lactation. Bovine somatotropin increased the numbers of follicles (6 to 15 mm) in lactating cows and size of second largest ovarian follicles in both lactating and nonlactating cows. Lactating cows developed dominant follicles that were larger and less estrogenic than those of nonlactating cows.

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)

Ovarian follicular populations in lactating dairy cows treated with recombinant bovine somatotropin (sometribove) or saline and fed diets differing in fat content and energy

Interactions of dietary energy and fat with recombinant bST (sometribove) injections were tested for their effects on ovarian function. Lactating dairy cows were fed one of three diets differing in energy concentration (NEL) and percentage of DM of calcium salts of long-chain fatty acids: diet 1, 1.68 Mcal/kg and 0%; diet 2, 1.68 Mcal/kg and 2.2%; and diet 3, 1.78 Mcal/kg and 2.2%. Cows were injected daily with bST or saline during one of two 19-d interestrous periods (crossover design) in which ovarian follicles were measured by ultrasonography. The bST-treated cows produced more FCM and were in lower energy balance than saline-treated cows. Before d 12 (first follicular wave, estrus = d 0), bST-treated cows had more ovarian follicles in classes 1 (3 to 5 mm; cows on diet 3) or 2 (6 to 9 mm; cows on diets 1 and 2) than saline-treated cows. After d 12 (preovulatory follicular wave), numbers of follicles in different size classes were similar for bST-treated and saline-treated cows, but cows fed diet 2 had larger preovulatory follicles. Lower dietary energy and bST treatment were both associated with larger subordinate follicles. Ovarian follicles less than 10 mm were stimulated by bST, and calcium salts of long-chain fatty acids increased diameters of preovulatory follicles.

Mechanism-based design of prolactin receptor antagonists

The mechanism of action of two forms of the prolactin (PRL) receptor was studied using analogs of human growth hormone (hGH). At low concentrations (approximately 1 pM), hGH binds and stimulates proliferation of Nb2 cells containing the 391-residue PRL receptor as well as murine lymphoid FDC-P1 cells transfected with the 591-residue hPRL receptor. However, at high concentrations (approximately 70 microM) hGH inhibits proliferation of both these cell lines. Such a "bell-shaped" hormone response curve was observed for hGH stimulation of the hGH receptor (Fuh, G., Cunningham, B.C., Fukunaga, R., Nagata, S., Goeddel, D. V., and Wells, J.A. (1992) Science 256, 1677-1680) and is consistent with the sequential formation of an active hormone-(receptor)2 complex in which hGH binds through a first site (Site 1) to a first receptor and then through a second site (Site 2) to a second receptor. By analogy to hGH activation of the hGH receptor, we find that hGH variants that are mutated in Site 1 or Site 2 are greatly reduced as agonists. Similarly, only Site 2 mutants are potent antagonists of either hGH or hPRL stimulated cell proliferation. These and other data support the notion that hGH and hPRL activate the PRL receptor by sequential dimerization and provide a rational basis for the design of potent antagonists to the prolactin receptor.