Changes in NSILA-S in response to somatotropin administration and hypophysectomy

Endocrine and cellular physiology and pathology of the insulin-like growth factor acid-labile subunit

The acid-labile subunit (ALS) of the insulin-like growth factor (IGF) binding protein (IGFBP) complex, encoded in humans by IGFALS, has a vital role in regulating the endocrine transport and bioavailability of IGF-1 and IGF-2. Accordingly, ALS has a considerable influence on postnatal growth and metabolism. ALS is a leucine-rich glycoprotein that forms high-affinity ternary complexes with IGFBP-3 or IGFBP-5 when they are occupied by either IGF-1 or IGF-2. These complexes constitute a stable reservoir of circulating IGFs, blocking the potentially hypoglycaemic activity of unbound IGFs. ALS is primarily synthesized by hepatocytes and its expression is lower in non-hepatic tissues. ALS synthesis is strongly induced by growth hormone and suppressed by IL-1β, thus potentially serving as a marker of growth hormone secretion and/or activity and of inflammation. IGFALS mutations in humans and Igfals deletion in mice cause modest growth retardation and pubertal delay, accompanied by decreased osteogenesis and enhanced adipogenesis. In hepatocellular carcinoma, IGFALS is described as a tumour suppressor; however, its contribution to other cancers is not well delineated. This Review addresses the endocrine physiology and pathology of ALS, discusses the latest cell and proteomic studies that suggest emerging cellular roles for ALS and outlines its involvement in other disease states.

Endocrine influences on serum acid-ethanol soluble non-suppressible in insulin-like activity (NSILA-S)

Serum levels of the acid-ethanol soluble component of non-suppressible insulin-like activity (NSILA-S) have been measured by bioassay in patient with hyperprolactinaemia, hypothyroidism, thyrotoxicosis and diabetes mellitus, and in normal subjects administered prednisone, oestrogens of androgens. Hyperprolactinaemia per se did not influence serum NSILA-S, however when GH was deficient prolactin hypersecretion may have maintained serum NSILA-S. Thyroid hormones, insulin and steroids did not appear to influence serum NSILA-S. These results suggest that regulation of the serum concentration of NSILA-S is not a common effector mechanism by which these hormones influence statural growth in man.

The occurrence of a distinct high molecular weight form of serum non-suppressible insulin-like activity

Gel filtration of acromegalic or normal serum at acid pH gave two distinct species of non-suppressible insulin-like activity (NSILA), one of high MW and the other of low MW (approximately 7000 daltons). The acid-stable high MW form remained high MW on rechromatography in acid. Gel filtration of serum at neutral pH however, gave only high MW activity, which remained high MW when rechromatographed under neutral conditions but split into both high and low MW forms when rechromatographed in acid. These results indicate that there are at least two circulating forms of NSILA--a low MW form which circulates in serum bound to a carrier protein in an acid-labile high MW complex and a species which circulates only as a stable, discrete high MW protein.