Radioimmunoassay of a Basic Somatomedin: Comparison of Various Assay Techniques and Somatomedin Levels in Various Sera*

Bala, R. M.; Bhaumick, B.

doi:10.1210/jcem-49-5-770

Cited by 93 publications

(26 citation statements)

References 25 publications

(24 reference statements)

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“…My collaborator Sylvia van Buul-Offers found that bovine placenta contains both types receptors and developed an RRA allowing to measure both IGF-I and -II using the same tissue [236]. RIAs were developed for SM-C by Furlanetto et al [16]and Bala and Bhaumick [237]and others, and for SM-A by Hall et al [238]. These, of course, measured IGF-I.…”

Section: Sf As Endocrine Substancementioning

confidence: 99%

A Personal View on the Early History of the Insulin-Like Growth Factors

Brande¹

1999

Horm Res Paediatr

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Salmon and Daughaday, when trying to set up an in vitro assay for Growth Hormone (GH), failed to obtain a direct effect on sulphate uptake in cartilage of hypophysectomized (hypox) rats. They recognised that this was not the consequence of poor methodology or materials, but an encrypted message from the examined system. They decided to turn around and to try and decipher it. Treatment with GH appeared to render hypox rat serum active in stimulating sulphation in hypox rat cartilage. They proposed that GH induced an intermediary substance, responsible for this biological effect: sulphation factor (SF), later renamed to Somatomedin(s) (SM). This hypothesis met with great criticism and very few took on to study this hypothetical substance. Besides disbelief, slow progress was also due to initial lack of a practical assay and to the failure to find a tissue with enriched concentration from which to extract the activity. From experimental evidence, the concept gradually evolved that SF/SM was insulin-like and might be identical to NSILA (non-suppressible insulin-like activity). This again generated controversy. This characteristic was too far away from the known effects of GH to be readily acceptable as a physiological phenomenon. The subsequent recognition of the distinct characteristics of the receptors for SM/NSILA and insulin, the discovery of the SM/NSILA binding proteins and, much later, a beginning understanding of their interactions, modifications and breakdown, have gradually resolved this apparent contradiction. When the sequence of two NSILA molecules became known, they were named IGF-I and -II. Structural similarity with proinsulin and identity of IGF-I with SM-C and -A were established and it was found that Multiplication Stimulating Activity (MSA), a growth factor isolated from fetal calf serum and subsequently from conditioned media of a rat liver cell line, was the rat equivalent of IGF-II. Structure-function relations could be studied, a quest which is not yet brought to an end. Meanwhile, the endocrine profile of SF/SM had gradually emerged by measuring plasma levels with bioassays. The main determinants were found to be age, body size, GH and the nutritional state. Later, radioimmunoassays were developed, enabling consolidation and detailing of these early observations, and allowing explorations at the tissue level. As another aspect of the endocrine paradigm, in vivo effects of IGFs were studied. The initial demonstration of an effect of crude preparations on longitudinal growth in experimental animals raised heavy scepticism, since the effect might have been an artefact caused by contaminants. It took confirmation with highly purified preparations and biosynthetic IGF-I to ease this concern. Still, not until recent years it was demonstrated, by knocking out the genes, that a true physiological and not a pharmacological effect had been induced previously.When it was found that most tissues produce SMs and are sensitive to their actions, the concept emerged that IGFs may have para- and autocrine fu...

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Section: Sf As Endocrine Substancementioning

confidence: 99%

A Personal View on the Early History of the Insulin-Like Growth Factors

Brande¹

1999

Horm Res Paediatr

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“…The acidic-neutral group (pI less than 7.4) includes IGF-II (1), SM-A (4), and multiplication-stimulating activity (5). The basic group of somatomedins are highly similar in terms of their molecular weights, pls, NH2-terminal amino acid sequences (1-3), and immunoreactivity (3,6,7). IGF-I (similar to our basic SM) and IGF-II have different NH2-terminal amino acid sequences but share a sequence homology with each other and with proinsulin (8).…”

mentioning

confidence: 99%

“…Insulin was a gift from Eli Lilly. Peptides were iodinated by a modification of the chloramine-T method (6) to specific activities of 100-150 ,uCi of basic SM and 80-100 pCi of insulin per Ag (1 Ci = 3.7 x 1010 becquerels).…”

mentioning

confidence: 99%

Somatomedin receptor of human placenta: solubilization, photolabeling, partial purification, and comparison with insulin receptor.

Bhaumick¹,

Bala²,

Hollenberg³

1981

Proc. Natl. Acad. Sci. U.S.A.

127

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Using a recently isolated human basic somatomedin (basic SM) similar to insulin-like growth factor I (IGF-I), we studied both the photoaffinity-labeled and unlabeled basic-SM receptor solubilized from human placental cell membranes. Unlike the result with the insulin receptor, high yields of soluble basic-SM-binding activity are obtained with Triton X-100. The soluble basic-SM receptor retains high-affinity (Kd 0.3 nM) peptide-specific binding of basic SM, similar to the binding present in particulate placenta membranes; the receptor exhibits a comparatively low affinity for insulin (k d 3 FAM). On Sepharose 6B, like the crude soluble insulin receptor, the basic-SM receptor migrates as a species with an apparent Stokes radius of 7.2 nm; unlike the insulin receptor, the basic-SM receptor does not, under similar conditions, yield a smaller binding species (apparent Stokes radius 3.8 nm). Upon photoaffinity labeling with "I-labeled basic SM, one principal specifically labeled constituent is detected. Upon gel electrophoresis in the presence of 2-mercaptoethanol, the photolabeled constituent, like the insulin receptor, migrates as a species with an apparent molecular weight of about 140,000; in the absence of reducing agent, a molecular weight greater than 240,000 is observed. Lectin-agarose affinity chromatography yields a 30-fold purification both of the basic-SM-binding activity and the photolabeled constituent. Anti-insulin receptor antibody does not appear to precipitate the basic-SM receptor. We conclude that the basic-SM receptor of human placenta is a glycoprotein, remarkably similar to (an isoreceptor) but distinct from the insulin receptor previously characterized in this tissue.The somatomedins (SM) are a group of growth hormone-dependent, serum-borne, polypeptide growth factors that have in common the ability to stimulate proteoglycan synthesis in cartilage and to mimic the actions of insulin in a variety of extraskeletal tissues. The somatomedins account for the insulinlike activity in human serum that is not neutralized by anti-insulin antibody (so-called nonsuppressible insulin-like activity or NSILA; recently renamed insulin-like growth factors or IGFs). Recent evidence suggests that all of the reported somatomedins may fall into two main groups based on their isoelectric points. The basic group (pIs greater than 7.4) includes insulin-like growth factor-I (IGF-I) (1), SM-C (2), and a basic SM that has been purified in our laboratory (3). The acidic-neutral group (pI less than 7.4) includes IGF-II (1), SM-A (4), and multiplication-stimulating activity (5). The basic group of somatomedins are highly similar in terms of their molecular weights, pls, NH2-terminal amino acid sequences (1-3), and immunoreactivity (3, 6, 7). IGF-I (similar to our basic SM) and IGF-II have different NH2-terminal amino acid sequences but share a sequence homology with each other and with proinsulin (8). Thus, there is a complex relationship between insulin, the somatomedins, and the peptide-specific receptors for eac...

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“…The sensitivity of RIA for this antiserum was 10-25 pg/tube with 50% displacement at 125 pg/tube (0.25 ng/ ml). Thus, the sensitivity for IGF-I of this antiserum seem to be better than those reported previously (Bala & Bhaumick, 1979;Baxter et al, 1982;Furlanetto et al, 1977;Zapf et al, 1981). Using this RIA, we measured plasma IGF-I levels in various clinical conditions.…”

Section: Discussionmentioning

confidence: 46%