Ultrastructural and morphometric changes in somatotropic cells following intraventricular administration of Met-enkephalin to rats.
An ultrastructural and morphometric study of Kurosumi et al. (1986) on type 1 GH cells in adult Sprague-Dawley rats, after the intraventricular administration of Met-enkephalin, with or without prior intraperitoneal administration of naloxone, was carried out and then compared to the same cellular type of untreated animals and of animals intraventricularly treated with distilled water, used as controls. The study demonstrated an increase of cellular (p < 0.05) and nuclear (p < 0.05) areas, an enlargement and dilation of the cisternae of the Golgi complex, with an increase in the Golgi area (p < 0.01) and the immature granules (p < 0.01); a greater development of the rough endoplasmic reticulum and an increase in the number of exocytosis (p < 0.01) and, only in male rats, an increase in the mature secretory granules (p < 0.01). The prior administration of naloxone prevented the appearance of these changes and also produced an increase (p < 0.01) of the organelles involved in the crinophagic phenomenon. These results suggest that the opioids play a modulating role, stimulating the synthesis and secretion of GH, which affects the ultrastructural features of the hypophyseal GH cells.