Agaricus bisporus lectin (PHA-B) stimulates insulin release in vitro. The stimulation is associated with increased conversion of proinsulin to insulin in the isolated islets of Langerhans of rats. Both these functions are directly proportional to the binding of I125 PHA-B, which is more marked in the islets from younger rats. The lectin binding to islets is not affected by glucose concentration in the medium.

Agaricus↗

PubMedDate not supplied

Effect of some novel synthetic analogues of CCK-4 on insulin and glucagon secretion.

The biologic activities of three synthetic analogues of CCK-4 (Trp-Met-Asp-Phe-NH2) in which (i) the C-terminal residue Phe was N-methylated (peptide I); (ii) the C-terminal Phe residue was N-methylated and Ser is substituted for Met in position 2 (peptide II); (iii) Pro was substituted for Trp in position 1 and the C-terminal amino nitrogen was methylated (peptide III), have been described. Peptides I and II have been found to inhibit the release of both insulin and glucagon, while peptide III was found to be a potent releasing agent for insulin and an inhibitor for glucagon.

Amino Acid Sequence↗

PubMedDate not supplied

Effect of age on Agaricus bisporus PHA-B stimulated insulin release and 45Ca2+ uptake in vitro by islets of Langerhans.

The in vitro basal insulin release and 45Ca2+ uptake by rat islets of Langerhans remain unaffected by the animal's age. However, when Agaricus bisporus lectin PHA-B is added to the medium, there is a significant stimulation of basal insulin secretion and 45Ca2+ uptake. The islets isolated from younger rats are more sensitive to A. bisporus PHA-B stimulation and register 1.5-fold and 3-fold more increases of insulin release and 45Ca2+ uptake respectively as compared to islets isolated from 12-month-old rats. Age-related conformational changes in the B-cell membrane are suggested as a possible explanation for the above observation.

Aging↗

PubMedDate not supplied

Insulin like activity in (-) epicatechin.

Water extract of the bark of plant of Pterocarpus marsupium Roxb is used as an antidiabetic drug in indigenous medicine in India. (-) Epicatechin, its active principle, has been found to be insulinogenic. The present in vitro study reports some insulin like activities of (-) epicatechin. Like insulin, (-) epicatechin stimulates oxygen uptake in fat cells and tissue slices of various organs, increases glycogen content of rat diaphragm in dose-dependent manner with corresponding increase in U14-C glucose uptake, and inhibits theophylline induced lipolysis in isolated fat pads in dose-dependent manner. Experiments on competitive binding of 125I-insulin and (-) epicatechin to liver cell plasma membrane indicate that insulin does not share binding site with (-) epicatechin. (-) Epicatechin at a concentration of up to 1 mM does not effect the release of glucagon from the islets in vitro. Thus, (-) epicatechin has insulinogenic as well as insulin like properties.

Adipose Tissue↗

PubMedDate not supplied

Synthetic analogs of cholecystokinin terminal tetrapeptide that stimulate insulin but not glucagon release from pancreatic islets.

Two synthetic analogs of CCK-4, Glp-Met-Asp-Phe-NH2 (I) and Pro-Met-Asp-Phe-NH2 (II) reported earlier to stimulate insulin release from the isolated rat pancreatic islets in vitro at concentrations as low as 10(-10) M, have now been found to be totally ineffective as glucagon releasers at concentrations as high as 10(-6) M or higher. It is evident that the replacement of Trp in CCK-4 by Glp and Pro residues leads to peptides which exhibit insulin releasing activity without stimulating the release of glucagon.

Animals↗

PubMedDate not supplied

Selective stimulation of insulin secretion by CCK-4 analogues having N-terminal modifications.

Synthetic analogues of CCK-4 in which Trp was replaced by D-Pro (peptide I), Thz (peptide II) and delta Pro (peptide III) have been studied for their insulin and glucagon releasing activities from the islets of Langerhans in vitro. Peptide I has been found to be the most potent insulin releaser among the three analogues and its activity is comparable to that of CCK-4. Unlike CCK-4, its three analogues (peptides I-III) do not stimulate the release of glucagon with basal concentration of glucose in the medium. However, with increasing glucose concentration, all the three analogues potentiate the glucose stimulus for insulin release.

Animals↗