Solomon A. Berson

RADIOIMMUNOASSAY OF GASTRIN.

Summary A highly specific radioimmunoassay for endogenous human plasma gastrin was developed using guinea pig antisera to crude porcine gastrin. Highly purified 125 I-porcine gastrin I, further purified on starch gel electrophoresis after labeling, was employed as tracer, and an anionic exchange resin was used to separate bound and free labeled gastrin. Sensitivity is better than 5 pg per ml. Cholecystokinin-pancreozymin and amino-terminal and carboxyl-terminal gastrin peptides cross-react only poorly in the gastrin-antigastrin system. Plasma gastrin and standard gastrin show parallel inhibition curves against the labeled porcine gastrin. Reproducibility of determinations in different assays is demonstrated. Plasma gastrin is unaffected by boiling for 5 to 10 min. High values of plasma gastrin were observed in 5 patients with Zollinger-Ellison syndrome and in 17 patients with pernicious anemia. Administration of HCl per os or into the stomach in 5 patients with pernicious anemia produced an acute fall in plasma gastrin concentration; the half-time for disappearance of gastrin from plasma was as short as 7 min.

Hypoglycemia: a potent stimulus to secretion of growth hormone.

In normal subjects, hypoglycemia produces an abrupt and sustained rise in levels of human growth hormone in plasma. This effect is independent of insulin, glucagon, or epinephrine. Prolonged fasting is accompanied by a rise in the hormone level in plasma. Measurement of this hormone after induced hypoglycemia is a specific test for pituitary somatotropic function.

Radioimmunoassay of ACTH in plasma

Techniques are described in detail for a radioimmunoassay of plasma adrenocorticotropin (ACTH) that is capable of detecting hormone in unextracted normal human plasma at 1:5 dilution under the conditions described. The sensitivity of the assay is at the level of 1 mumug/ml (equivalent to 0.014 mU/100 ml). In normal subjects ACTH concentrations averaged 22 mumug/ml (equivalent to 0.308 mU/100 ml) plasma at 8-10 a.m. In a smaller group the concentrations averaged 9.6 mumug/ml (equivalent to 0.134 mU/100 ml) at 10-11 p.m. Although a circadian rhythm in normal subjects was not always well marked throughout the daytime hours, plasma ACTH usually fell to its lowest value in the late evening. In hospital patients who were not acutely ill, concentrations were infrequently above 100 mumug/ml in the morning and usually fell to significantly lower levels in the late evening. Severely ill hospital patients occasionally exhibited a.m. concentrations above 200 mumug/ml. In a group of subjects showing frequent spiking of plasma 17-OHCS concentrations throughout the day parallel spiking of plasma ACTH as well was generally observed.Metyrapone produced marked increases in plasma ACTH within 24 hr in all cases and generally within 3-6 hr except when started late in the day. Dexamethasone brought about a persistent reduction in plasma ACTH in a patient under continued treatment with metyrapone.Hypoglycemia, electroshock, surgery under general anesthesia, histalog and vasopressin administration were usually followed by significant increases in plasma ACTH concentration. Prior administration of dexamethasone blocked the response to hypoglycemia. Marked elevations in plasma ACTH were observed in patients with adrenal insufficiency off steroid therapy, in Cushings disease after adrenalectomy even in the presence of persistent hypercortisolemia, and in some untreated patients with Cushings disease. Umbilical cord blood contained higher plasma ACTH concentrations than maternal blood at delivery in seven of eight cases. After suppression of ACTH secretion by dexamethasone or cortisol. ACTH disappeared from plasma with half-times ranging from 22 min to 30 min in three cases studied.

Plasma Insulin Concentrations in Nondiabetic and Early Diabetic Subjects: Determinations by a New Sensitive Immuno-assay Technic

For many years insulin was regarded as only weakly antigenic, or even, according to some, as essentially nonantigenic. However, a few years ago, during the course of investigations on the metabolism of I-labeled insulin, it was observed that the tagged insulin showed a prolonged retention in the blood stream of all subjects who had received insulin therapy, and it was demonstrated that this behavior was attributable to the presence of insulin-binding antibodies. Since the concentration of antibody is extremely low in most such patients and since the insulin-antibody complexes do not precipitate, certain special technics, including the use of an isotopically labeled insulin, are required for the detection of the antibody. Further extension of these technics has made possible an immunologic method for the assay of very small amounts of insulin.

Size heterogeneity of immunoreactive human ACTH in plasma and in extracts of pituitary glands and ACTH-producing thymoma

Abstract Immunoreactive ACTH in plasma and in extracts of pituitary glands and ACTH-producing thymoma was demonstrated using Sephadex gel filtration and separatory ultracentrifugation to be composed of at least two major components, one ACTH-like and the other of considerably greater molecular size. The relative distribution between the two major components varied greatly among plasmas. It is concluded that the larger molecular weight fraction originates in the pituitary and represents ACTH bound in covalent linkage to a larger peptide.

Size and Charge Distinctions Between Endogenous Human Plasma Gastrin in Peripheral Blood and Heptadecapeptide Gastrins

The major fraction of immunoreactive plasma gastrin in peripheral blood, cross-reacting in a radioimmunoassay system with 125I-porcine gastrin I, exhibits less acidic behavior on starch gel and paper electrophoresis and a larger molecular size on Sephadex gel filtration than that shown by heptadecapeptide gastrins. The plasma hormone is not altered by boiling and could not be shown to be converted by antral aqueous extracts to heptadecapeptide-like gastrin. From the electrophoretic and filtration behavior of plasma gastrin, it is suggested that the major fraction of the plasma hormone is a molecule of approximately 7000 mol wt containing heptadecapeptide gastrin linked to a more basic peptide. A small fraction of plasma hormone exhibits characteristics similar to heptadecapeptide gastrin.

Some current controversies in diabetes research.

Among the disputed questions considered in this presentation are (1) Relationships between a) the known metabolic abnormalities in diabetes and the development of microangiopathy, and b) insulin antibodies and nodular glomerulosclerosis; (2) Sensitivity to insulin and availability of insulin in idiopathic diabetes mellitus and in other conditions associated with impaired glucose tolerance; (3) The role of pituitary growth hormone in the etiology of idiopathic diabetes; (4) The status of “bound insulin,” ILA, etc.; and (5) The identification of the “synalbumin” insulin antagonist as the B chain of insulin. Also included are the presentation of data on insulin and growth hormone-secretory responses to glucose loading in obese and nonobese diabetic and nondiabetic subjects and a discussion of the interrelationships among the peptide hormones, glucose and free fatty acids in blood.

The Influence of Blood Glucose on the Plasma Concentration of Growth Hormone

A sensitive and specific assay method has been used to demonstrate acute changes in plasma HCH in normal and diabetic subjects. HGH secretion is suppressed by glucose administration and markedly stimulated by hypoglycemia, by a rapid fall in blood glucose without hypoglycemia, and by interference with intracellular glucose utilization. High levels of HGH were also observed during prolonged fasting, after exercise, and four to six hours following oral glucose administration. Abnormalities in HGH secretion were found in association with acromegaly and obesity, and following section of the hypophyseal stalk. The half time for disappearance of endogenous plasma HGH is twenty to thirty minutes.

Nature of Immunoreactive Gastrin Extracted from Tissues of Gastrointestinal Tract

Extracts of mucosa from human antrum, duodenum, and proximal jejunum obtained at surgery and at autopsy contain two immunoreactive components of gastrin, separable on the basis of size and charge. These components exhibit the same characteristics as the two plasma gastrin components identified earlier. The major plasma component (BG) has a less acidic charge and larger molecular size than heptadecapeptide gastrin; the minor plasma component (H-LG) resembles heptadecapeptide gastrin in both respects. H-LG predominates in most extracts of antral mucosa, but the relative abundance of BG increases distally, being the only detectable component (although at very low concentration) in proximal jejunal mucosal extracts. Both components are immunochemically indistinguishable from the two plasma components and from heptadecapeptide porcine gastrin.

Quantitative aspects of iodine metabolism. The exchangeable organic iodine pool, and the rates of thyroidal secretion, peripheral degradation and fecal excretion of endogenously synthesized organically bound iodine.

The technical methods employed and the schematic model on which the analyses are based are common to all the determinations and are presented first. The specific analyses and results obtained for the various phases of iodine metabolism are then considered in separate sections. An attempt has been made to follow a similar order of presentation in each of these sections. The theoretical basis for the methods employed in the measurement of each aspect of iodine metabolism is followed by a sample calculation from the observed data in one of the subjects, R. D. Reference is then usually made to the results of the measurements, and the section is concluded with an analysis of the validity of the determinations and the sources of error.