Quantitation of insulin stores in Langerhans islets by combined immunohistochemistry and computerized microspectrophotometric analysis.

Histology, size, and insulin content of Langerhans islets from normal and recent experimental hyperthyroid (REH) dogs were studied. Insulin localization in the islets was revealed by immunohistochemistry, and the remaining two variables were analyzed by computerized microspectrophotometry according to an original technique described here. Observed under the light microscope, the REH dog pancreas section shows larger than normal islets whose scarce beta-granules are mainly located near B-cell borders and grouped along capillaries. The brown areas occupied by insulin in Langerhans islets from REH and normal dogs (mean +/- SEM) are 5182 +/- 311 and 4236 +/- 287 microns2, the total mean insulin amount per respective islet section-as expressed in absorbance arbitrary units-is 1108 and 1846, and the light absorbances per such area units are 0.214 +/- 0.070 and 0.436 +/- 0.060, respectively. Measuring these variables in dog and human (large) pancreases by the conventional methods successfully used for small pancreases would have been technically impossible.