THE VOLUMETRIC DISTRIBUTION OF THE PANCREATIC ISLET TISSUE IN YOUNG AND OLD RATS

Abstract

The equations derived by Wicksell for the relation between the size distribution of the section surfaces and the actual volume distribution of spherical and ellipsoid bodies have been used in order to calculate the distribution of the islet volume in 75 male rats of ages varying from the new-born to 480 days. The animals were fed a diet containing 38% calories from carbohydrate, 24.5% from fat and 37.5% from protein. The volume frequency curves for all age groups appeared to have a normal distribution and this was confirmed by transformation of data to probits. Irrespective of age, it could be stated that in individual rats a larger islet volume caused a displacement of the normal curve to the right toward the larger islet classes. If the comparison is limited to animals within the same age class, this holds on the average. The increase of islet volume with age is manifested by an increase of the volumes in all classes, but is especially true for large islets. The resulting right shift in the volume frequency distribution curve was, however, less than would be expected from the increase in total islet volume.