In Vitro and in Vivo Behaviour of Rat Islets of Langerhans Treated with MHC Antisera and Complement2)

A partially purified secretory granule fraction, isolated from rat islets of Langerhans by differential centrifugation, was used for investigating the stability of the beta granules during incubation in various conditions. Effects of pH, temperature, and time were studied; the granules possessed optimal stability at 4° and pH 6.0, and could be solubilized at pH 4.0 or 8.5, or in the presence of sodium deoxycholate, but not by phospholipase c, ouabain, or alloxan. Incubation with glucose or some of its metabolites, or with tolbutamide, ATP, or cyclic 3',5'-AMP did not alter the stability of the beta granules Exogenous insulin-131I was not bound by the isolated granules under the conditions used; no specific insulin-degrading activity could be detected in subcellular fractions of the islets. These findings indicate that intracellular solubilization of the granules with subsequent diffusion of the insulin into the extracellular space is not a likely mode of insulin secretion in vivo, and suggest that a crystalline zinc-insulin complex may exist in the matrix of the beta granules.

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The effect of cooling rate and culture on in vitro insulin release in isolated rat islets of Langerhans

Cryobiology ◽

10.1016/0011-2240(88)90396-3 ◽

1988 ◽

Vol 25 (6) ◽

pp. 542-543

Author(s):

J. Foreman ◽

M.J. Taylor ◽

H. Moriya

Keyword(s):

Cooling Rate ◽

Insulin Release ◽

Islets Of Langerhans ◽

Rat Islets ◽

Isolated Rat Islets ◽

In Vitro Insulin Release ◽

Rat Islets Of Langerhans ◽

Isolated Rat

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Transplantation and in vitro perifusion of rat islets of Langerhans after slow cooling and warming in the presence of either glycerol or dimethylsulfoxide

Cryobiology ◽

10.1016/0011-2240(82)90231-0 ◽

1982 ◽

Vol 19 (6) ◽

pp. 661

Author(s):

M.J. Taylor ◽

T.J. Duffy ◽

S.R.Q. Morgan ◽

P.J. Davisson

Keyword(s):

Islets Of Langerhans ◽

Slow Cooling ◽

Rat Islets ◽

Rat Islets Of Langerhans

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Pentitols and insulin release by isolated rat islets of Langerhans

Biochemical Journal ◽

10.1042/bj1090333 ◽

1968 ◽

Vol 109 (3) ◽

pp. 333-339 ◽

Cited By ~ 72

Author(s):

W Montague ◽

K W Taylor

Keyword(s):

Insulin Release ◽

Islets Of Langerhans ◽

Pentose Phosphate ◽

Rat Islets ◽

Isolated Islets Of Langerhans ◽

Isolated Rat Islets ◽

Rat Islets Of Langerhans ◽

Stimulate Insulin Release ◽

Isolated Rat

1. Insulin secretion was studied in isolated islets of Langerhans obtained by collagenase digestion of rat pancreas. In addition to responding to glucose and mannose as do whole pancreas and pancreas slices in vitro, isolated rat islets also secrete insulin in response to xylitol, ribitol and ribose, but not to sorbitol, mannitol, arabitol, xylose or arabinose. 2. Xylitol and ribitol readily reduce NAD+ when added to a preparation of ultrasonically treated islets. 3. Adrenaline (1μm) inhibits the effects of glucose and xylitol on insulin release. Mannoheptulose and 2-deoxy-glucose, however, inhibit the response to glucose but not that to xylitol. 4. The intracellular concentration of glucose 6-phosphate is increased when islets are incubated with glucose but not with xylitol, suggesting that xylitol does not promote insulin release by conversion into glucose 6-phosphate. 5. Theophylline (5mm) potentiates the effect of 20mm-glucose on insulin release from isolated rat islets of Langerhans, but has no effect on xylitol-mediated release. These results indicate that xylitol does not stimulate insulin release by alterations in the intracellular concentrations of cyclic AMP. 6. A possible role for the metabolism of hexoses via the pentose phosphate pathway in the stimulation of insulin release is discussed.

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Stimulation of insulin secretion from isolated rat islets of Langerhans by melittin

Bioscience Reports ◽

10.1007/bf01121020 ◽

1984 ◽

Vol 4 (8) ◽

pp. 665-671 ◽

Cited By ~ 18

Author(s):

Noel G. Morgan ◽

William Montague

Keyword(s):

Insulin Secretion ◽

Islets Of Langerhans ◽

Maximal Response ◽

Secretory Rate ◽

Rat Islets ◽

Cell Plasma ◽

Rat Islets Of Langerhans ◽

Dose Dependent ◽

Stimulation Of

Melittin, an amphipathic polypeptide, stimulated the secretion of insulin from rat islets of Langerhans incubated in vitro. The secretory response was dose-dependent and saturable with half the maximal response elicited by a melittin concentration of 4 μg/ml. The response was rapid in onset, an increase in secretion occurring within 2 rain of exposure of the islets to melittin (2 μg/ml). An enhanced secretory rate could be maintained for at least 40 rain in the presence of melittin but declined steadily when the agent was removed. Stimulation of secretion by melittin occurred in the absence of glucose and in the presence of both 4 mM and 8 mM glucose but not in the presence of 20 mM glucose. The effect of melittin on secretion was dependent on the presence of extracellular calcium but was not inhibited by norepinephrine. The data suggest that melittin may be a valuable agent for further study of the role played by the B-cell plasma membrane in the regulation of insulin secretion.

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