Immunochemical properties of the aminopropeptide of procollagen type III

Growth hormone doping in sports: a critical review of use and detection strategies

GH is believed to be widely employed in sports as a performance-enhancing substance. Its use in athletic competition is banned by the World Anti-Doping Agency, and athletes are required to submit to testing for GH exposure. Detection of GH doping is challenging for several reasons including identity/similarity of exogenous to endogenous GH, short half-life, complex and fluctuating secretory dynamics of GH, and a very low urinary excretion rate. The detection test currently in use (GH isoform test) exploits the difference between recombinant GH (pure 22K-GH) and the heterogeneous nature of endogenous GH (several isoforms). Its main limitation is the short window of opportunity for detection (~12-24 h after the last GH dose). A second test to be implemented soon (the biomarker test) is based on stimulation of IGF-I and collagen III synthesis by GH. It has a longer window of opportunity (1-2 wk) but is less specific and presents a variety of technical challenges. GH doping in a larger sense also includes doping with GH secretagogues and IGF-I and its analogs. The scientific evidence for the ergogenicity of GH is weak, a fact that is not widely appreciated in athletic circles or by the general public. Also insufficiently appreciated is the risk of serious health consequences associated with high-dose, prolonged GH use. This review discusses the GH biology relevant to GH doping; the virtues and limitations of detection tests in blood, urine, and saliva; secretagogue efficacy; IGF-I doping; and information about the effectiveness of GH as a performance-enhancing agent.

Serum procollagen type III peptide levels in normal rhesus monkeys

Serum levels of the amino-terminal peptide of Type III procollagen (P-III-P) were assayed by radioimmunoassay in 48 Rhesus monkeys from 0.7 to 26.4 years of age. Serum P-III-P levels in ten juvenile monkeys (0.7-4.7 yrs.) were significantly higher (84.5 +/- 66.2 ng/ml, p = 0.05) and ranged from 29.6 to 238.0 ng/ml as compared with 38 monkeys over 5 years of age (21.7 - 9.4 ng/ml), which ranged from 8.5 to 55.5 ng/ml. No significant differences in serum P-III-P levels were observed between any age groups over 5 years of age (5-10, 10-15, 15-20, and > 20) or between male and female monkeys within any age category.

Two assays for measuring fibrosis: reverse transcriptase-polymerase chain reaction of collagen alpha(1) (III) mRNA is an early predictor of subsequent collagen deposition while a novel serum N-terminal procollagen (III) propeptide assay reflects manifest fibrosis in carbon tetrachloride-treated rats

Using a novel quantitative reverse transcriptase-polymerase chain reaction assay, we have determined the amount of specific mRNA for procollagen alpha(1) (III) (PIIIP) in the carbon tetrachloride (CCl(4)) model of liver fibrosis in rats. After a single week of CCl(4) application, the amount of PIIIP mRNA was increased approximately 10 times over the untreated control group and continued to increase to approximately 30 times after 7 weeks of intoxication. In this model substantial fibrosis was demonstrated by computer-aided morphometry after 5 to 7 weeks of treatment. Using recombinant murine N-terminal procollagen alpha(1) (III) propeptide (PIIINP), a novel sensitive immunoassay for the measurement of circulating PIIINP in rodent sera was established. An increase in PIIINP serum levels was observed after 5 to 7 weeks of CCl(4) intoxication. Our results suggest PIIIP gene expression is an early marker of tissue fibrosis. Early PIIIP gene expression is correlated with the extent of the subsequent fibrosis. PIIIP mRNA levels increase much earlier than conventional histological examination or PIIINP levels. PIIINP measurements with our new serum assay, on the other hand, are a good noninvasive marker of manifest fibrosis but are a poor marker of fibrogenesis.

Serum procollagen III peptide concentration in iron overload

Patients with severe iron overload may develop hepatic fibrosis due to iron toxicity. Unfortunately, the follow-up of the fibrogenic activity during treatment by histological examination of tissue biopsies carries potential side effects, and may therefore not be justified ethically. Recently, the serum concentration of procollagen type III peptide (S-PIIINP) has been shown to be a valid serum marker of the activity of collagen metabolism in conditions with hepatic fibrosis unrelated to iron overload. In order to evaluate the potential usefulness of this test in patients with fibrosis due to iron overload, we investigated the relationship between the PIIINP serum concentration and the size of iron overload in 18 patients with hereditary haemochromatosis (HH) and in 14 patients with transfusional iron overload. A close correlation was found between S-ferritin and S-PIIINP (r = 0.73, p < 0.0001). Follow-up of 6 patients during iron depletion treatment revealed a normalization of the serum aminotransferase concentration before normalization of S-PIIINP was found. This may indicate that excess iron directly induces an increase in fibrogenesis rather than the increased fibrogenesis is secondary to hepatocellular injury caused by iron excess. Thus, serial measurements S-PIIINP may be useful in follow-up of the fibrogenic process due to iron overload.

A radioimmunoassay for the N-terminal propeptide of rat procollagen type III. Application to the study of the uptake of the N-terminal propeptide of procollagen type III in isolated perfused rat liver

Antibodies against a synthetic peptide representing the 14 C-terminal amino acids of the N-terminal propeptide of rat and bovine procollagen type III were raised in rabbits and used to develop a radioimmunoassay. N-Terminal propeptide of procollagen type III, purified from calf skin, served as standard and tracer material. The IC50 of the standard inhibition curve was 2.1 micrograms/l, the lower limit of detection about 0.4 microgram/l, interassay variation was 8.5% and the intraassay variation 6.6% in typical experiments. Three peaks of antigenicity were detected in rat serum after gel chromatography. One peak coeluted with purified N-terminal propeptide of procollagen type III, one peak contained material approximately twice this size, and one peak eluted close to the void volume of the column. The antigen concentration in rat serum decreased in an age dependent manner. Rat, bovine, sheep and minipig serum antigen was sufficiently crossreactive to allow the application of the assay to these species, whereas human, goat and guinea pig samples were not. The degradation product Col 1, causing non-parallel inhibition in commercially available assays for human samples was not recognized since it does not contain the epitope represented by the synthetic peptide. The assay was used to study the half-life of bovine and endogenous N-terminal propeptide of procollagen type III in isolated perfused rat liver. [125I]-labeled antigen was cleared rapidly from the perfusate (t1/2 less than 5 min). The bovine antigen was removed from the perfusate with a half-life of 15 +/- 4 min. Endogenous propeptide was perfused for 120 min with little change in concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Markers of collagen and basement membrane metabolism in sera of patients with progressive systemic sclerosis

The concentrations of the amino terminal propeptide of type III procollagen, the 7S domain of type IV collagen, and the fragment P1 of laminin (PIIINP, 7S, and P1 respectively) and the activity of galactosylhydroxylysyl glucosyltransferase (GGT) in serum were evaluated as indicators of disease activity in a cross sectional study of 84 patients with progressive systemic sclerosis. The mean values of PIIINP, P1, and GGT were raised in progressive systemic sclerosis, 19-32% of patients having abnormal values of the various tests. PIIINP, measured with two different assays, and P1 were associated with active, acute, or subacute disease. GGT also correlated positively with some acute phase proteins in the whole group, without a clear association with the course of the disease. Arthritis was associated with increased PIIINP concentrations as well as with an increased activity of GGT. Kidney disease led to raised concentrations of the degradation products of PIIINP. Raynaud's phenomenon in the hands was related to increased PIIINP concentrations.

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

Detection of procollagen biosynthesis using peptide-specific antibodies

Peptides corresponding to selected sequences of the alpha 1 chain of the COOH propeptide of type I and type III human procollagen were synthesized and used as antigens to develop polyclonal and monoclonal antibodies. The antibodies were shown to be epitope specific using a peptide-based solid phase enzyme-linked immunoadsorbent assay. The antibodies were specific for the appropriate procollagens and the COOH propeptides isolated from serum-free culture supernatants of human skin fibroblasts. The rabbit antisera directed to the type I synthetic peptide bound the intact procollagen molecule and both the procollagen alpha 1(I) and alpha 2(I) chains after the reduction of the disulfide bonds. In addition, the antisera bound intact type I COOH propeptide, generated by bacterial collagenase treatment of procollagen, and the individual chains of the propeptide after reduction. In contrast, a monoclonal antibody to the type I peptide was able to bind only to the reduced form of the COOH propeptide. Both rabbit polyclonal and murine monoclonal antibodies directed to the type III synthetic peptide bound the intact and the individual chains of type III procollagen as well as the intact and reduced forms of the type III COOH propeptide. The antibodies have been used to detect procollagen synthesis in two human osteosarcoma cell lines and the differential expression of procollagen in the culture medium of rat lung fibroblasts grown in the presence or absence of glucocorticoids.

Serum procollagen type III N-terminal peptides and laminin P1 peptide in alcoholic liver disease

The appearance of perivenular fibrosis on liver biopsy reflects the beginning of the fibrotic process that ultimately results in liver cirrhosis. To examine whether the fibrogenic activity can be detected by blood tests, we evaluated whole antibody radioimmunoassay (RIA) of procollagen type III N-terminal peptides (P-III-P), RIA of these peptides using Fab fragments (Fab-P-III-P), and RIA of the laminin P1 peptide in alcoholics within 1 week of alcohol abstinence. The Fab-P-III-P levels in subjects with perivenular fibrosis were significantly higher than those in patients with simple fatty liver. Values in 63% of subjects with perivenular fibrosis exceeded the upper limit of the fatty liver group. Patients with simple fatty liver had significantly lower values than nonalcoholic controls. Serum levels of P-III-P and laminin were elevated in patients with alcoholic hepatitis and correlated well with the degree of inflammation. With abstinence, Fab-P-III-P levels increased in all alcoholics. P-III-P values increased in patients with normal P-III-P values on admission. By contrast, the values of laminin decreased during abstinence. Therefore, to interpret serum levels of Fab-P-III-P, P-III-P, and laminin, the duration of abstinence must be taken into consideration. P-III-P, Fab-P-III-P and laminin measurements in the serum within 1 week of abstinence can contribute to the detection of alcoholic liver disease and the determination of its stage.

Serum aminoterminal procollagen type III peptide in acute viral hepatitis. A long-term follow-up study

The development of chronic viral liver disease is associated with increased deposition of connective tissue in the liver. The aminoterminal propeptide of procollagen type III (P-III-NP) is considered to reflect the metabolism of collagen type III, one of the major collagen types in liver fibrosis. The purpose of the present study was to elucidate, whether S-P-III-NP in patients with viral hepatitis was related to injury and repair processes in the liver. S-P-III-NP was determined in a prospective longitudinal study of 63 patients with acute viral hepatitis followed to healing or development of chronic liver disease. Two assays were applied. The P-III-NP Ria-gnost assay, which measures mainly the intact propeptide, and the P-III-NP Fab-assay, in which the antibody exhibits equal affinity to the intact propeptide as well as the degradation product col 1. At the onset of viral hepatitis, S-P-III-NP determined in either assay was equally elevated in the two groups. From the second month of follow-up, significantly higher levels in both assays were observed in patients developing chronic disease. During follow-up, the highest P-III-NP RIA-gnost values were seen in patients with chronic active hepatitis, and active cirrhosis. S-P-III-NP decreased towards normal levels during development of inactive cirrhosis. In the individual patient, S-P-III-NP Ria-gnost was positively related to transaminases. During follow-up of uncomplicated hepatitis a normalization of transaminases occurred before normalization of S-P-III-NP RIA-gnost. Considering, that S-P-III-NP, in contrast to the conventional laboratory variables, reflects the metabolism of type III collagen, it is assumed that determination of S-P-III-NP may provide new information on fibrogenesis in viral liver disease.

Serum type III procollagen peptide concentrations in severe chronic active hepatitis: relationship to cirrhosis and disease activity

To analyze the correlations between the presence of cirrhosis and hepatocellular inflammation and the serum concentrations of the amino-terminal peptide of procollagen type III in chronic liver disease, we measured procollagen type III concentrations in paired serum samples from 46 patients (17 had cirrhosis) with severe chronic active hepatitis during a therapeutic treatment trial. Coded sera were analyzed for procollagen type III concentrations using both a standard and a recently described Fab radioimmunoassay to compare their relative diagnostic accuracy. Mean procollagen type III levels were elevated to the same extent in the cirrhotic and noncirrhotic groups at entry into the study. In response to immunosuppressive therapy, the initially elevated procollagen type III levels improved to normal values at remission in both groups. Qualitatively, the results were similar using either assay, but the standard assay was more sensitive for identifying the clinical stage of disease (i.e., active disease vs. disease in remission) than the Fab assay. Since both procollagen type III levels and standard liver function tests correlated well individually with the presence or absence of active disease, they also correlated with each other when both entry and remission values were considered. However, procollagen type III levels correlated poorly with indicators of inflammation (histologic grade and serum transaminase levels) during active disease. It is concluded that procollagen type III levels change in concert with standard liver function tests but do not quantitatively reflect inflammation or static measurements of hepatic fibrosis in severe chronic active hepatitis. However, these preliminary results suggest that procollagen type III can distinguish active disease from chronic active hepatitis in remission.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum concentrations of laminin and aminoterminal propeptide of type III procollagen in relation to the portal venous pressure of fibrotic liver diseases

In sera of patients with fibrotic liver diseases (n = 33) classified histologically into various degrees of liver fibrosis (n = 21) and cirrhosis (n = 12) the concentrations of the basement membrane protein laminin and of its pepsinresistant fragment P1 and of the N-terminal propeptide of type III procollagen were determined. The concentrations of both proteins were related to the portal venous pressure measured in these patients. Compared with the reference population (n = 146) the concentration of laminin increases from 1.04 U/ml (normal persons) to 1.69 +/- 0.46 U/ml in liver fibrotic and 2.58 +/- 0.87 U/ml in liver cirrhotic patients. Although the concentrations of the propeptide of type III procollagen increase also there exist only weak correlations between both connective tissue proteins in serum. Laminin is correlated highly positive with the portal venous pressure in cirrhotic subjects (r = 0.9206), the extent of laminin elevation reflects closely the degree of portal hypertension. Virtually all of the fibrotic patients having a laminin concentration within the reference range had a normal portal venous pressure. The data suggest laminin as a potentially useful parameter for monitoring the portal venous pressure in cirrhotic and severe fibrotic patients.

Serum laminin--its concentration increases with portal hypertension in cirrhotic liver disease

The concentrations in serum of the high molecular weight glycoprotein laminin and of the N-terminal propeptide of type III procollagen were determined in various histologically proven fibrotic liver diseases (n = 33), of which the portal venous pressure has been measured indirectly. The concentrations of both biomatrix proteins were related to the portal venous pressure. Laminin in serum of normal persons (n = 146) ranged from 0.81 to 1.43 U/ml. Compared with the mean normal concentration (1.04 U/ml) the glycoprotein is increased in fibrotic liver lesions in parallel with the severity of the fibrotic organ transformation reaching the highest values (2.58 +/- 0.87 U/ml, P less than 0.001) in liver cirrhosis (n = 12). The level of N-terminal propeptide of type III procollagen increased similarly, but the concentrations of both matrix proteins exhibit only weak statistical correlations (r = 0.6680). The level of laminin is correlated strongly with the elevation of the portal venous pressure in cirrhotic (r = 0.9206) and fibrotic (r = 0.7157) subjects. For the propeptide of procollagen the respective correlation is r = 0.4808. Molecular sieve chromatography reveals a heterogeneous composition of laminin-related antigens in serum with two main molecular weight fractions of 700 and 300 kD, respectively.

Serum amino-terminal type III procollagen peptide in rheumatoid arthritis. Relationship to disease activity, treatment, and development of joint erosions

Using 2 radioimmunoassays, increased serum levels of amino-terminal type III procollagen peptide and its degradation products were demonstrated in rheumatoid arthritis patients. Patients with active disease showed higher serum propeptide levels than did patients with inactive disease. Unlike D-penicillamine, azathioprine treatment suppressed the propeptide levels in patients with active disease. A 6-month prospective study showed significantly higher initial serum propeptide levels in patients with erosive progression. The propeptide level reflects disease activity and may be a valuable prognostic marker in rheumatoid arthritis.

Purification and characterization of the N-terminal propeptide of human type III procollagen

The N-terminal propeptide of type III procollagen was purified from human ascitic fluid by using (NH4)2SO4 precipitation, DEAE-Sephacel chromatography at pH 8.6, Sephacryl S-300 chromatography and another DEAE-Sephacel chromatography at pH 4.5. The Mr of the human peptide was about 42 000, which corresponds in size to the propeptide released by the specific N-proteinase during the extracellular processing of collagen. Bacterial-collagenase digestion of the human peptide produced three fragments, which could be separated on a Bio-Gel P-10 column. The human propeptide and its collagenase-derived fragments, an N-terminal non-collagenous domain Col 1, a C-terminal non-helical domain Col 2 and a collagenous domain Col 3, resembled those derived from the N-terminal segment of bovine type III procollagen in their amino acid composition. The human peptide was found to contain sulphate, which may explain its extremely low isoelectric point (3.1). Antibodies against the human N-terminal propeptide reacted similarly with both the purified human peptide and a corresponding segment of bovine type III procollagen. The human propeptide could be used in developing radioimmunoassays for monitoring fibrotic processes.

Radioimmunoassay for the amino-terminal sequences of type III procollagen in human body fluids measuring fragmented precursor sequences

Antisera specifically directed against the amino-terminal precursor sequence of bovine p-N-collagen type III (Col 1-3 III) have been raised in rabbit. When tested in a radioimmunoassay, parallel displacement curves and complete cross-reactivity were observed between bovine and human purified Col 1-3 III. However, these displacement curves were not parallel to that obtained with serially diluted human sera which presented a smoother slope. Cleavage of the Col 1-3 III peptide by collagenase at high temperature yielded an immunoreactive preparation containing two smaller peptides (Col 1 plus Col 2) III. The displacement curves obtained with human or bovine (Col 1 plus Col 2) preparations were parallel to those obtained with serially diluted human sera or other human body fluids (amniotic and ascitic fluids). Quantitative measurements of the circulating antigen in normal and pathological conditions are possible only when the (Col 1 plus Col 2) is used as standard antigen. This radioimmunoassay represents an original and simple technique offering good accuracy. The amount of (Col 1 plus Col 2) III in human adults is 69.1 +/- 27.7 ng/ml, with a distribution of frequency close to the normal. It is increased in liver cirrhosis and other conditions characterized by an active neoformation of connective tissue.

Complete amino acid sequence of the N-terminal extension of calf skin type III procollagen

The N-terminal extension peptide of type III procollagen, isolated from foetal-calf skin, contains 130 amino acid residues. To determine its amino acid sequence, the peptide was reduced and carboxymethylated or aminoethylated and fragmented with trypsin, Staphylococcus aureus V8 proteinase and bacterial collagenase. Pyroglutamate aminopeptidase was used to deblock the N-terminal collagenase fragment to enable amino acid sequencing. The type III collagen extension peptide is homologous to that of the alpha 1 chain of type I procollagen with respect to a three-domain structure. The N-terminal 79 amino acids, which contain ten of the 12 cysteine residues, form a compact globular domain. The next 39 amino acids are in a collagenase triplet sequence (Gly- Xaa - Yaa )n with a high hydroxyproline content. Finally, another short non-collagenous domain of 12 amino acids ends at the cleavage site for procollagen aminopeptidase, which cleaves a proline-glutamine bond. In contrast with type I procollagen, the type III procollagen extension peptides contain interchain disulphide bridges located at the C-terminus of the triple-helical domain.