Morphologic variations of the pituitary pars intermedia of viscacha during long and short photoperiod.

ACOSTA, MARIANO; FILIPPA, VERÓNICA; MOHAMED, FABIAN

Huerta Grande, Córdoba.

Congreso; Primera Reun. Conjunta de Sociedades de Biol. de la Rep. Argentina, XVI J. Cient. de la Soc. de Biol. de Cba., IX J. de la Soc. Argentina de Biol, XXV Reun. Anual de la Soc. de Biol. de Cuyo.; 2007

Soc. de Biol. de Cba., Soc. Arg. de Biol., Soc. de Biol. de Cuyo, Soc. de Biol. de Rosario, y Asoc. de Biol. de Tucum.

The viscacha (Lagostomus maximus maximus) is a rodent of nocturnal habits and photoperiod-depend seasonal reproduction. The pituitary pars intermedia (PI) of Lagostomus shows a developed parenchyma, with granulated and non-granulated (folliculo-stellate; FS) cells, typical follicular structures and scanty blood vessels. The aim of this work was to study the morphology of PI in adult male viscachas during long (summer) and short (winter) photoperiod. Histochemical (PAS), immunohistochemical (antibodies anti-α-MSH, anti-ACTH, anti-S-100 and anti-GFAP), and morphometric (area percentage, cells and follicular number, major colloidal diameter, major cellular and nuclear diameters to immunolabeling cells) studies were carried out. The FS cells show cytoplasmic and nuclear staining for anti-S-100 and cytoplasmic staining for anti-GFAP. These cells are distributed throughout the parenchyma and they are originating PAS-positive follicles. There are granulated cells near follicles and limiting with the pars nervosa, where there are important blood vessels. Most parameters show a significant decrease during short photoperiod. Our results demonstrate that the PI parenchyma of adult male viscachas is composed by granulated and FS cells closely associated. The PI morphology and histoarchitecture varies according to the different photoperiods.