Immunocytochemical and immunoelectron-microscopic study of somatotrophs inICR and nonobese diabetic mice

Somatotrophs (GH cells) were classified immunoelectron microscopically into th ree types mainly on the basis of the size of secretory granules in the mouse pituitary of ICR strain. Type I cells contained large secretory granu les. Type II cells contained both large secretory granules and small secret ory granules. Type III cells contained small secretory granules. All three types of GH cells were found from the neonatal ages to adult. The relative proportion of three types did not change with age, and no sex differences i n the relative proportion of the cell types were detected. Type I cells pre dominate in all age groups observed. In 60-day-old male mice percentages of each type were as follows: type 1 93.7 +/- 0.1%, type II 5.4 +/- 0.8%, and type III 0.9.0 +/- 0.4% (n = 5), and in 60-day-old female mice type I 95.2 +/- 0.1%, type II 2.7 +/- 0.5%, and type III 2.1 +/- 0.9% (n = 5). The max imum diameters of the large secretory granules increased from 7 to 60 days of age. The small secretory granules similarly increased in size in female mice, but those in male mice did not change. In the diabetic female mice of the nonobese diabetic (NOD) strains, GH cells in diabetic mice became smal ler, and the number and size of secretory granules decreased, indicating di minished GH secretion n. However, the relative proportion of each subtype o f GH cells did not differ irrespective of the occurrence of diabetes. Copyr ight (C) 2000 S. Karger AG, Basel.