Characterisation of the 5 kDa growth hormone isoform

Growth hormone: isoforms, clinical aspects and assays interference

The measurement of circulating concentrations of growth hormone (GH) is an indispensable tool in the diagnosis of both GH deficiency and GH excess. GH is a heterogeneous protein composed of several molecular isoforms, but the physiological role of these different isoforms has not yet been fully understood. The 22KD GH (22 K-GH) is the main isoform in circulation, followed by 20KD GH (20 K-GH) and other rare isoforms. Studies have been performed to better understand the biological actions of the different isoforms as well as their importance in pathological conditions. Generally, the non-22 K- and 20 K-GH isoforms are secreted in parallel to 22 K-GH, and only very moderate changes in the ratio between isoforms have been described in some pituitary tumors or during exercise. Therefore, in a diagnostic approach, concentrations of 22 K-GH accurately reflect total GH secretion. On the other hand, the differential recognition of GH isoforms by different GH immunoassays used in clinical routine contributes to the known discrepancy in results from different GH assays. This makes the application of uniform decision limits problematic. Therefore, the worldwide efforts to standardize GH assays include the recommendation to use 22 K-GH specific GH assays calibrated against the pure 22 K-GH reference preparation 98/574. Adoption of this recommendation might lead to improvement in diagnosis and follow-up of pathological conditions, and facilitate the comparison of results from different laboratories.

Screening hybridomas for anabolic androgenic steroids by steroid analog antigen microarray

BACKGROUND

Currently, dozens of anabolic androgenic steroids (AAS) are forbidden in the World Anti-Doping Agency Prohibited List, however, despite extensive investigation, there are still lots of AAS without corresponding monoclonal antibodies.

RESULTS

A steroid analog antigen microarray made up of ten AAS was fabricated to screen the hybridoma and it was found an original unsuccessful clone turned out to be a candidate anti-boldenone antibody, without any cross-reactions with endogenous AAS or 44 different AAS standard reference materials tested.

CONCLUSION

Our findings suggested that steroid analog antigen microarray could be a promising tool to screen and characterize new applications of antibodies for structure analogs, and this also exhibits the potential to fast identify effective epitopes of hybridomas in a single assay.

Immunological screening and characterization of highly specific monoclonal antibodies against 20 kDa hGH

Background: hGH has been widely abused as a doping agent in sports for many years. There are some important approaches for the detection of hGH doping, and the ratio of 22:20 kDa GH was considered one of the most suitable detection indicators of GH abuse. Currently, effective anti-GH antibodies and related reagents are needed to develop a detection method, in particular, highly specific anti-20 kDa hGH monoclonal antibodies are a prerequisite. Herein we constructed the expression vector of 20 kDa hGH and prepared the corresponding antibodies by the immunization of the recombinant human 20 kDa into mice. Positive clones that can specifically recognize 20 kDa hGH were screened and characterized by enzyme immunoassay, Dot-ELISA and surface plasmon resonance. In total, 14 specific monoclonal cell lines were screened out. Results: By a series of characterization, it was found that the 6C8, 44H3, 12G7 and 33Y19 clones were showing much higher specificity and affinity to 20 kDa hGH, and P3H9 could recognize both 20 and 22 kDa hGH isoforms. 6C8 and 44H3 matched well with P3H9 in the surface plasmon resonance testing. The 12G7 clone had the best surface properties with an association constant of 3.4 × 109 M-1 and a dissociation constant of 2.95 × 1010 M. Conclusion: Highly specific monoclonal antibodies against 20 kDa hGH were generated, and also two paired antibodies (P3H9 and 6C8 or P3H9 and 44H3) were characterized, which can serve as the potential components for 22:20 kDa detection kit.

Biochemical polymorphism of the growth hormone system proteins and its manifestations in human prostate cells

The basic mechanisms are considered that are responsible for producing biochemical polymorphism of human proteins realized at three basic levels: the structures of genome and genes; the transcription and maturation of transcripts; the postsynthetic formation of functionally active protein products of gene expression. The data on biochemical polymorphism of growth hormone (GH) and some other proteins that are directly or indirectly necessary for its functioning and support this polymorphism by polylocus, polyallelism, alternative splicing, and various postsynthetic modifications are analyzed. The role of polymorphic proteins of the GH system is discussed in formation of a variety of oligomeric molecular structures of this system (multicomponent transport complexes, receptors, and endocellular protein ensembles involved in the regulation of gene expression). It is emphasized that such structural polymorphism significantly influences the biological effects in various parts of the GH system during physiological processes and in tumors, in particular in prostate cancer.

Bioanalysis and Analytical Services Research Group at The Municipal Institute for Medical Research IMIM-Hospital del Mar, Spain

Analytical laboratories involved in health-related research are becoming a fundamental part of the advancement of science in this field. Of particular interest to clinical, legal, toxicological, forensic and environmental matters is the analysis of drugs and medications present in biological fluids of consumers or exposed subjects. The established sensitive and reliable work of sports drug-testing laboratories represents an interesting example of a multidisciplinarity approach toward widespread bioanalytical problems. The experiences reported in this article will be of general interest, especially for analysts studying the determination of substances in biological material.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.

Generation of 5 and 17 kDa human growth hormone fragments through limited proteolysis

INTRODUCTION

The reported presence of two fragments of 5 and 17 kDa originating from the 22 kDa human growth hormone (hGH) in blood and tissues, postulated as the sequences AA 1-43 and AA 44-191, has led to the hypothesis of a post-translational proteolytic origin with respect to the abundant 22 kDa variant (AA 1-191). To evaluate this hypothesis, the activity of several endo-proteases on the 22 kDa hGH protein has been evaluated.

METHODS

Proteolysis using pepsin, trypsin, V8-protease, proteinase K and thermolysin were explored under several conditions, including incubation time and pH. Results were monitored by MALDI-TOF and HPLC-ESI mass spectrometry. Proteolytic 5 and 17 kDa fragments were purified through reversed phase HPLC-UV, and their immuno-affinity properties evaluated by surface plasmon resonance.

RESULTS

Thermolysin was shown to target mainly the AA 43-44 bond of the 22 kDa sequence at physiological pH. Interaction studies of the purified fragments with anti-GH antibodies showed some reactivity for the 17 kDa fragment.

CONCLUSIONS

Thermolysin processes hGH generating 5 and 17 kDa fragments, demonstrating the feasibility of this reaction, although the enzyme responsible for this process in humans is still unknown. Specific antibodies should be used to detect these fragments in human specimens, and, at the same time, the 17 kDa fragment could constitute an interference in some hGH immunoassays.

Surface plasmon resonance immuno assays - A perspective

Human growth hormone (GH) represents an extremely challenging task from an anti-doping viewpoint. GH is an endogenously produced substance, present at very low levels in circulation (for the most abundant 22kDa isoform approximately 50pM in plasma and 100fM in urine) either as monomer or homo- and heterodimers, comprises a family of distinct isoforms, and obeys a pulsatile secretion routine that is affected by many different internal and external factors. Upon administration of the recombinant, single-isoform pharmaceutical, the feedback mechanism reduces the endogenous heterogeneity resulting in altered ratios between the different GH isoforms. Thus, measuring the isoform ratios through immuno assays appears the approach of choice. Conventional assays do not provide information on isoform-specific association and dissociation events of the individual primary antibody-isoform or isoform-secondary antibody interactions. This particular information can be obtained using the technology of surface plasmon resonance (SPR) which enables monitoring of biomolecular interactions in a dynamic and label-free setting. In this paper the different aspects of SPR are described, how the technology may be beneficial for understanding today's anti-GH immunoassays, and whether the approach could be employed for measuring GH in the near future.

Detection of doping with recombinant human growth hormone

Detection of doping with recombinant human growth hormone is one of the challenges for antidoping analysis. This review focuses on the most important relevant publications that provide insight into the laboratory measurement of human growth hormone (hGH), antibodies and standards, the isoform approach and the biomarker approach. The isoform approach monitors the changes of hGH molecular isoform composition in serum and was applied at the Olympic Games in Athens in 2004, Turin in 2006 and Beijing in 2008. The markers approach detects a formula score, which reflects the changes in concentration of IGF-1 and P-III-P. All these methodologies measure the concentrations of growth hormone and its isoforms for isoform approach, or the concentrations of IGF-1 and P-III-P. All factors that affect these measurements should be taken into account for the development of methods to detect doping with recombinant hGH.