A Sensitive, Precise Radioimmunoassay of Serum Insulin Relying on Charcoal Separation of Bound and Free Hormone Moieties

Albano, J. D. M.; Rp, Ekins; Maritz, Gert S.; Turner, R. C.

doi:10.1530/acta.0.0700487

Cited by 645 publications

(285 citation statements)

References 0 publications

Supporting

Mentioning

281

Contrasting

Unclassified

Order By: Relevance

“…Plasma glucose concentrations were measured on the day of sampling by a glucose oxidase procedure [23]. Plasma insulin concentrations were measured on samples stored at −20°C by a radioimmunoassay procedure [24]. Plasma C-peptide concentrations were measured using the radioimmunoassay kit supplied by Guildhay (Surrey, UK).…”

Section: Methodsmentioning

confidence: 99%

Loss of beta cell function as fasting glucose increases in the non-diabetic range

2004

View full text Add to dashboard Cite

Aims/hypothesis. Our aim was to define the level of glycaemia at which pancreatic insulin secretion, particularly first-phase insulin release, begins to decline. Methods. Plasma glucose and insulin concentrations were measured during an IVGTT in 553 men with non-diabetic fasting plasma glucose concentrations. In 466 of the men C-peptide was also estimated. IVGTT insulin secretion in first and late phases was assessed by: (i) the circulating insulin response; (ii) population parameter deconvolution analysis of plasma C-peptide concentrations; and (iii) a combined model utilising both insulin and C-peptide concentrations. Measurements of insulin sensitivity and elimination were also derived by modelling analysis.Results. As fasting plasma glucose (FPG) increased, IVGTT first-phase insulin secretion declined by 73%, 71% and 68% for the three methods respectively. The FPG values at which this decline began, determined by change point regression, were 4.97, 5.16 and 5.42 mmol/l respectively. The sensitivity of late-phase insulin secretion to glucose declined at FPG concentrations above 6.0 mmol/l. Insulin elimination, but not insulin sensitivity, varied with FPG. IntroductionThe respective roles of insulin deficiency and insulin resistance in the development of Type 2 diabetes mellitus remain controversial [1,2]. In response to a glucose stimulus, two phases of insulin secretion may be distinguished [3]. The first occurs as an immediate response to a rise in blood glucose concentrations. Low first-phase insulin release is an early abnormality in deteriorating glucose homeostasis and predicts the subsequent development of Type 2 diabetes [4,5,6,7]. Late-phase insulin release is more prolonged, but of lesser amplitude. It includes the progressively increasing second phase of insulin secretion seen in response to sustained hyperglycaemia [3], and also the compensatory insulin secretion that is the feedback response to a continued increase in circulating glucose. This late-phase insulin secretion may seem to be preserved even when glucose metabolism is defective,In the course of this work, our colleague and co-author James Jeffs died unexpectedly after a short illness. His contribution will be greatly missed.

show abstract

Section: Methodsmentioning

confidence: 99%

Loss of beta cell function as fasting glucose increases in the non-diabetic range

2004

View full text Add to dashboard Cite

show abstract

“…Triplicate batches of 10 islets in glass vials containing 1 ml Kreb's Ringer Buffer (KRB), 10 mmol/l 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES), 0.5 % bovine serum albumin (BSA), glucose (2.8, 8.3, 27.7 mmol/l), were incubated for 60 min in a 37°C shaking water bath. The medium was separated from the islets by gentle centrifugation (500 rev/min 5 min at 10°C) and stored at -20°C pending insulin measurement by radioimmunoassay (RIA) [20].…”

Section: Methodsmentioning

confidence: 99%

Beta-cell hypersensitivity to glucose following 24-h exposure of rat islets to fatty acids

1997

View full text Add to dashboard Cite

“…Islets were usually perifused for 30 min to establish stable insulin secretory rates and then exposed to various agonists indicated in the figure legends. Perifusate samples were collected at time intervals indicated in the figures and 200 Ixl aliquots analysed for 3H content when appropri-W. Zawalich: Memory in rat islets involves phosphoinositide hydrolysis ate as well as insulin [12] using rat insulin (Lilly and Co., Indianapolis, Indiana, USA # 615-1963-12-3) as standard. In some experiments the nature of the 3H-containing molecules was assessed in pooled perifusate samples collected during the final 10 min of the perifusion.…”

Section: Methodsmentioning

confidence: 99%

Time-dependent potentiation of insulin release induced by alpha-ketoisocaproate and leucine in rats: possible involvement of phosphoinositide hydrolysis

Zawalich

1988

Diabetologia

View full text Add to dashboard Cite

Summary. The ability of the amino acid leucine and its keto acid, alpha-ketoisocaproate, to induce insulin release, to initiate phosphoinositide hydrolysis, and to amplify the subsequent insulin secretory response to glucose was assessed. In islets whose inositol-containing lipids were prelabelled with myo [2-3H]inositol, the addition of either compound resulted in an increase in insulin output, an increase in 3H effiux, rapid and significant increases in labelled inositol phosphate accumulation and a sustained increase in 3H efflux after removal of the stimulant. Direct measurements of labelled inositol phosphate accumulation in islets previously stimulated with alpha-ketoisocaproate demonstrate that this sustained increase in ~H effiux was the result of a persistent increase in phosphoinositide hydrolysis and was not simply a consequence of the hydrolysis of preformed inositol phosphates into more membrane permeable species. Prior exposure of islets to alpha-ketoisocaproate or leucine also resulted in an amplified secretory response to a subsequent glucose (10 mmol/1) stimulus. While peak first phase insulin release averaged 66+_4 (mean +_ SEM, n=18) pg.islet -1. min -1 from control islets, this value increased to 204+_14 and 246_+ 11 pg. islet-1. min-1 in the leucine or alpha-ketoisocaproate pretreated islets respectively. The duration of this amplified response paralleled the duration of the persistent increase in 3H effiux. Prior alpha-ketoisocaproate exposure also amplified the subsequent insulin secretory response to tolbutamide and glyceraldehyde. While control (non-pretreated) islets in response to tolbutamide (200 I.tmol/l) released insulin at a rate of 50+6 pg.islet-l.min -1 (n=3), this first phase response increased to 506+_38 pg.islet -lrain -1 in prior alpha-ketoisocaproate treated islets. Peak first and second phase insulin responses to glyceraldehyde were increased 5-fold and 2-fold, respectively, by prior alpha-ketoisocaproate. These results suggest that events coupled to the hydrolysis of membrane inositol-containing phospholipids induced by leucine and alpha-ketoisocaproate participate not only in their acute insulin stimulatory action, but also in their ability to induce time-dependent potentiation (memory) in isolated islets.Key words: Islets, phosphoinositides, memory, insulin secretion, leucine, alpha-ketoisocaproate, 3H efflux.It is well established that prior glucose stimulation of pancreatic B cells results in an amplified insulin secretory response to a second glucose challenge [1][2][3][4]. Some characteristics of this phenomenon, termed timedependent potentiation (TDP) by Grill and associates [2,3] have been established: (a) glucose must be metabolised to induce TDP; (b)TDP develops within minutes and persists long after removal of the initial stimulant; (c)intracellular accumulation of cAMP does not seem to play a major role in the process; and (d) glyceraldehyde and the gut hormone cholecystokinin [5] mimic to a large extent this sensitising effect of glucose. We recently reported ...

show abstract

A Sensitive, Precise Radioimmunoassay of Serum Insulin Relying on Charcoal Separation of Bound and Free Hormone Moieties

Cited by 645 publications

References 0 publications

Loss of beta cell function as fasting glucose increases in the non-diabetic range

Loss of beta cell function as fasting glucose increases in the non-diabetic range

Beta-cell hypersensitivity to glucose following 24-h exposure of rat islets to fatty acids

Time-dependent potentiation of insulin release induced by alpha-ketoisocaproate and leucine in rats: possible involvement of phosphoinositide hydrolysis

Contact Info

Product

Resources

About