Arved Roovete

A radioimmunoassay was developed for somatomedin-binding protein isolated from human amniotic fluid. The mean level in amniotic samples from 20-22 week of gestation was high, 51 micrograms/ml. Human serum and serum fraction gave dose-response curves superimposable on that for the pure amniotic binding protein. Gel chromatography of serum at neutral pH disclosed immunoreactive binding protein only in fractions with a molecular size of 35 000 corresponding to elution volume for the low molecular form somatomedin-binding protein. The mean levels (mean and range) of immunoreactive somatomedin-binding protein in cord blood (191 ng/ml, 55-1698 ng/ml) and in diabetic patients with uraemia (97 and 51-174 ng/ml) were 5- to 10-fold elevated above those of healthy adults (23 and 18-36 ng/ml). In acromegaly the levels decreased with increasing GH production (r = -0.77; P less than 0.005). In adult patients with GH deficiency the levels were 2-fold elevated in comparison with healthy subjects. Apart from patients with uraemia a negative correlation was found in adults between the levels of immunoreactive binding protein and immunoreactive IGF-I which reflect the GH production (r = -0.81, P less than 0.001).

ABSTRACT The double antibody technique of Hales & Randle (1963) for determination of insulin in plasma was developed for the assay of HGH in plasma. The precision and reproducibility of the method as well as the recovery of HGH added to plasma were highly satisfactory. Increased HGH values were obtained in acromegaly and during insulin hypoglycaemia, while decreased values were observed during glucose infusion. Successful treatment of acromegaly was accompanied by the return of plasma HGH levels toward normal. The plasma HGH values obtained with the present method cannot be considered as reflecting the absolute amounts of HGH, since several factors in the assay procedure, mainly the incubation time and the concentration of HGH antibodies used, markedly influenced the values obtained. It is questioned whether the radioimmunological assay methods for HGH per se give an absolute measure of this hormone in plasma.

The effect of oral glucose (1 g/kg BW) on levels of immunoreactive somatostatin (SLI) in peripheral venous plasma was investigated in young and older nondiabetic subjects (mean ages, 25.8 and 56.7 yr, respectively) as well as in subjects with decreased iv glucose tolerance (K value less than 1.0) and in diet-treated diabetic patients with fasting hyperglycemia (blood glucose, greater than 7.0 mmol/liter). SLI was assayed after extraction of plasma on silica glass beads. In control experiments (glucose omitted), SLI levels tended to decline. Ingestion of glucose was followed by a moderate (52% or less) increase in SLI levels in subjects with normal or decreased iv glucose tolerance. The stimulating effect was sustained for 90 or 120 min after glucose ingestion and the increase in plasma SLI was significant (P less than 0.05-0.02) whether in relation to prestimulatory values or control experiments. In contrast, in overtly diabetic patients, glucose ingestion was not followed by increased SLI levels. It is concluded that oral glucose stimulates SLI secretion in individuals of different ages and with varying degrees of glucose tolerance, but the response is impaired in type 2 diabetic patients with fasting hyperglycemia.