With the use of isolated rat islet perfusion, levels of the islet cyclic adenosine 3' ,5' -monophosphate (cAMP) were compared with dynamic insulin secretion induced by tolbutamide and arginine. Tolbutamide elevated islet cAMP rapidly and augmented both glucose-induced islet cAMP levels and insulin secretion; arginine, however, did not elevate islet cAMP but did enhance glucose-induced insulin secretion. Since the latter result could have been modulated by cyclic guanosine 3' ,5' -monophosphate, this cyclic nucleotide was also measured and found to remain unchanged during stimulation of insulin secretion by arginine and a combination or arginine and glucose. Thus, the action of tolbutamide appears to be modulated in part by cAMP, whereas arginine appears to augment insulin secretion independently of cyclic nucleotides.
Immunologically measurable insulin (IMI) in normal, obese and obese, diabetic subjects after intravenous administration of glucose, tolbutamide and glucagon.Summary. Serum insulin levels (immunologically measurable insulin, IMI) in normal, obese and obese, diabetic subjects were determined following injection of glucose {0.33 g/kg), tolbutamide (1 g) and glucagon (1 rag). --In normal non-obese subjects an immediate (after one minute) increase of serum insulin levels was observed following the injection of glucose, tolbutamide or glucagon. 15 minutes after injection, the IMI-values were within the normal range. Obese subjects also react with an immediate increase of serum insulin levels following injection of glucose, tolbutamide or gtucagon; however, the IMIvalues were significantly higher than in normal subjects. Furthermore, in obese patients with slight diabetes, the IMI-levels after glucose or tolbutamide were definitely lower than those observed in normal non-obese subjects, although the levels following glucagon were of the same magnitude.-Apparently the increase of endogenous insulin in obese non-diabetic-patients after administration of glucose does not influence the glucose assimilation coefficient, K. I-Iyperinsulinism appears to be associated with obesity rather than with diabetes.
The present study was designed to compare, in lean and obese nondiabetic subjects, basal and postprandial levels of peripheral venous plasma insulin, glucagon, gastrin, pancreatic polypeptide (PP), glucose, triglycerides, and somatostatin-like immunoreactivity (SLI) during the infusion of synthetic somatostatin-14 or saline. Thirty-five minutes before the ingestion of the test meal, an infusion of synthetic somatostatin-14 was started at a rate of 0.5 ng/kg X min and was increased to 1.0 ng/kg X min 30 min after consumption of the meal and lasted for another 90 min. During the infusion of saline, basal peripheral vein levels of insulin, gastrin, and triglycerides were elevated in obese subjects, whereas basal plasma SLI levels were significantly lower compared with the lean controls. Basal glucagon and PP levels were similar in both groups. After the ingestion of the meal, augmented concentrations of insulin and gastrin were observed in the obese subjects, whereas postprandial SLI and PP levels were reduced. Chromatography of fasting plasma revealed all measurable SLI to be confined to the void volume fractions of a Bio-Gel P-10 column. The rise in SLI after the meal was due to an increase of SLI co-eluting with somatostatin-28 and somatostatin-14. During the infusion of somatostatin, only basal insulin levels were significantly lower in the obese subjects, whereas no change of any basal hormone level was observed in the lean group. During the infusion of somatostatin, SLI levels were elevated by 20-30 pg/ml in both groups compared with the saline controls. During the infusion rate of 0.5 ng/kg X min, only postprandial PP levels were reduced significantly in the obese group, while all the other parameters were unaffected in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)
The method of Roos et al. (1963) for the preparation of HGH yields a highly purified biologically active hormone preparation suitable for clinical purposes and, after one additional purification step (chromatography on Sephadex G-200 according to Hunter (1965), for radioiodination. In the double antibody technique described, the labelled hormone can be used for radio-immunoassay without starch-gel or Sephadex purification. The method is simple and sensitive enough to permit the determination of HGH in serum.
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