An ultrastructural morphometric analysis of the adenohypophysis of lactating rats

Abstract

A morphometric analysis of the adenohypophysis (pars distalis) of lactating rats was carried out by a semi-automated method at the ultrastructural level. The cellular elements were identified by their ultrastructural morphology. The following values were considered for the morphometric study: numerical density of cells/mm³ of tissue and the percentage of parenchymal volume occupied by every cell type. Mammotropes (PRL cells) numbered 624 × 10³/mm³ and occupied 59.9% of the parenchymal volume (p.v.). Somatotropes (GH cells) numbered 206 × 10³/mm³ and occupied 15.0% of the p.v. Folliculo-stellate cells (FS cells) numbered 128 × 10³/ mm³ and occupied 8.1% of the p.v. Gonadotropes (GN cells) numbered 47 × 10³/mm³ and occupied 6.0% of the p.v. Adrenocorticotropes (ACTH cells) numbered 45 × 10³/Vmm³ and occupied 3.8% of the p.v. Thyrotropes (TSH cells) numbered 36 × 10³mm³ and occupied 3.4% of the p.v. PRL cells were characterized by aspects compatible with intense hormone production. GH cells did not show differences with those of nonlactating animals. Folliculo-stellate elements appeared hypertrophic with abundant cytoplasm, enlarged Golgi complex, and dilation of the follicular lumina. GN cells had abundant cytoplasm with a well-developed and dilated ergastoplasm, particularly in type II GN cells. ACTH cells did not show differences with those of nonlactating animals. TSH cells showed moderate nucleocytoplasmic activation. These fine structural morphometric findings are discussed in relation to other studies regarding nonlactating adenohypophysis and hormone changes during lactation.