Studies on insulin secretion and the pituitary insulin secretagogue beta-cell-tropin in the sand- XXXX (Psammomys obesus).

@entity1 @entity2175 @entity6 @entity28 @entity75 @entity4611 @entity35 @entity413
The sand- @entity35 (Psammomys obesus) is an animal model for the study of @entity1 @entity2175 onset @entity6 which appears to be controlled by caloric intake. In the present investigations, these animals have been studied in relation to the influence of low- and high-energy diets on body weight, plasma insulin and blood @entity413 levels, and on insulin secretion from the perfused pancreas and the secretion of @entity75 ( @entity75 , ACTH18-39) and the insulin secretagogue beta-cell-tropin (beta-CT, ACTH22-39) from the @entity4611 . The sand- @entity35 maintained on the high-energy diet all became @entity28 . Insulin secretion from the perfused pancreas of the @entity28 sand- @entity35 in the presence of 5.6 mM @entity413 was significantly higher than in the lean controls maintained on low-energy diets. Increasing the @entity413 concentration to 16.7 mM only produced a small stimulation of insulin secretion in the @entity28 animals, and the difference between the two groups was not significant. Stimulation of insulin secretion by beta-CT was variable, but the @entity28 animals appeared to be more responsive. @entity4611 were incubated for 4 h to measure the secretion of the ACTH related peptide. These were separated by gel filtration and the concentrations measured by radioimmunoassay with a @entity75 antiserum and a @entity75 standard. In all experiments beta-CT was 4-6 per cent of the total @entity75 immunoreactive material. In these experiments the @entity28 animals maintained on a high-energy diet were divided into two groups, those with plasma insulin levels less than 500 mu u/ml and those with insulin levels greater than 500 mu u/ml. The latter group had a significantly higher blood @entity413 level, presumably due to the insulin resistance resulting from the severe hyperinsulinaemia. It was also observed that @entity75 -IRM and beta-CT secretion was lower in this group than in the animals maintained on low-energy diets or those on high-energy diets with moderate hyperinsulinaemia. This suggests a possible feedback inhibition by insulin on the secretion of beta-CT.
