Morphometric evaluation of the pancreas of growth hormone-transgenic mice
Abstract
The pancreas of MTbGH-transgenic mice exhibiting high levels of circulating growth hormone was analyzed by morphometry. Mice that did not inherit the foreign gene served as controls. Animals were examined at an average age of 11 weeks. The volume of the unfixed pancreas was measured by fluid displacement. Cavalieri's principle was applied to estimate the volume of the pancreas and the total volume of the pancreatic islets after paraffin embedding. The volume fraction of immunostained B-cells in the islets was determined following Delesse’s principle. Total B-cell volume was obtained as the product of the fractional B-cell volume and the total volume of the endocrine pancreas. Values obtained for pancreas volume in paraffin embedded tissue were 44% lower on the average than the values obtained for the unfixed organ. The volume of the pancreas, the total islet volume and the volume fraction of islets in the pancreas as well as the islet volume-to-body weight ratio were significantly increased in GH transgenic mice, whereas the pancreas-to-body weight ratio did not differ from control values. The volume fraction of B-cells in the pancreatic islets was similar between groups. The changes noted in the endocrine pancreas of GH transgenic mice encompass both an increase in total B-cell volume and a concomitant increase in the volume of other islet cells.