Endocrine Abstracts

Ghrelin, the endogenous ligand of GH secretagogue receptor type 1a, has emerged as pleiotropic modulator of diverse biological functions, including energy homeostasis and recently, reproduction. The effects of i.c.v. administered ghrelin on morphological characteristics of pituitary FSH- and LH-cells were examined in adult male Wistar rats. The animals were randomized in two groups: control and experimental group, each consisted of seven animals, and implanted with an i.c.v. cannula. After a recovery period, experimental males received 1 μg ghrelin/5 μl PBS during 5 days, while control males received the same volume of saline vehicle. Experimental and control males were sacrificed under ether narcosis 2 h after the last injection. FSH- and LH-producing cells were studied using the peroxidase–antiperoxidase (PAP) immunohistochemical procedure. The FSH and LH cells of adult control males were polygonal, oval or polyhedral in shape with prominent, often eccentrically located nuclei. They were strongly immunohistochemically stained and positioned throughout the pituitary pars distalis, alone or in groups, often in close contact with blood capillaries. After i.c.v. treatment with ghrelin, FSH and LH cells in the pituitaries were smaller in size, less intensely immunostained and their shape was irregular comparing to the controls.

In animals i.c.v. treated with ghrelin volume of FSH cells and volume of their nuclei were significantly decreased (P<0.05) by 34.0 and 37.1% respectively, while these parameters of LH cells were unchanged when compared to the control values. The volume density of LH cells in animals i.c.v. treated with ghrelin was significantly decreased (P<0.05) by 38.9%, but the volume density of FSH cells was not altered in comparison with the controls. In conclusion, our results indicate that i.c.v. applied ghrelin have inhibitory effect on the volume of FSH cell and volume of their nuclei, as well as on relative volume density of LH cells.