Morphological and Morphometric Changes of Pituitary Lactotrophs of Viscacha (Lagostomus maximus maximus) in Relation to Reproductive Cycle, Age, and Sex

Abstract

Lactotrophs in pituitary pars distalis (PD) of viscacha were studied by immunohistochemistry and morphometric analysis in the following groups: 1) adult males throughout the reproductive cycle (reproductive, gonadal regression, and recovery periods), 2) melatonin-treated adults, 3) castrated adults, 4) prepubertal, 5) non-pregnant females, and 6) pregnant females (early, mid, and late pregnancy). Immunopositive percentage area (%IA), cell percentage in PD (% PDC), number of cells per reference area (no.cell/ RA), major cellular and nuclear diameters were analyzed. Lactotrophs were mainly localized in the ventro-medial region and the caudal extreme of PD. In the male viscachas, they were isolated in small and big groups, close to blood vessels and near follicles. These cells were pleomorphic and with a heterogeneous cytoplasmic immunolabeling pattern. In the adult males of the gonadal regression period the morphometric parameters were the lowest. Most parameters of lactotrophs in the prepubertal were significantly lower than in the adult males in the reproductive period. In the melatonintreated animals and in castrated animals there was a decrease in %IA, %PDC, and no.cell/RA. In the females, the morphometric parameters increased at the end of pregnancy. Non-pregnant females exhibited a higher immunopositive area and number, but a smaller size of cells than males. Our results showed that in the adult male viscacha, lactotrophs vary seasonally, probably due to the photoperiod effect through melatonin. Besides the changes observed after castration, in prepubertal animals, in adults of different sex, and during pregnancy suggest that the gonadal steroid hormones might modify the lactotrophs activity. Anat Rec, 293:150-161, 2010. V V C 2010 Wiley-Liss, Inc.

Androgen Receptors Expression in Pituitary of Male Viscacha in relation to Growth and Reproductive Cycle

“…The brain was rapidly exposed and the pituitary processed for light microscopy. The pituitaries were fixed in Bouin's fluid, embedded in paraffin, and sagittally sectioned (5 μ m thick), following the design used in previously reported studies [ 30 , 32 ].…”

“…In pituitary PD the activity of LH- and FSH-cells was different during the annual reproductive cycle, demonstrating that these cells do not secrete in parallel, and melatonin acts differentially on the gonadotroph activity [ 28 ]. In addition, corticotrophs, somatotrophs, thyrotrophs, and lactotrophs vary throughout the reproductive cycle [ 29 – 32 ]. A reduction of the testicular weight and of the seminiferous tubule diameters, seminiferous epithelium with Sertoli cells, spermatogonia and a few primary spermatocytes, and hypotrophic Leydig cells was observed in winter [ 33 , 34 ].…”

“…Earlier histological studies have described different pituitary PD zones, called ventral, medial, and dorsal regions and rostral and caudal ends. It has been demonstrated that pituitary cell types changed in relation to age and gonadal activity of viscachas [ 29 , 30 , 32 ]. Changes in the immunostaining for AR and LH- and FSH-cells have been recently reported in the pituitary of castrated adult male viscachas.…”

Histological and histochemical study of the duodenum of the plains viscacha (Lagostomus maximus) at different stages of its ontogenetic development

“…) and some endocrine glands and sense organs (Romera et al . , ; Filippa and Mohamed ). However, researches on the digestive system morphology of the plains viscacha are scarce and they refer to the weight and size of the digestive tract and accessory glands (Llanos and Crespo ).…”

Ion channel noise shapes the electrical activity of endocrine cells

“…Mathematical models of endocrine pituitary cells often neglect the role of cell size, even though there are substantial variations in the size of these cells, with cell diameters ranging from 7 to 15 μm [33,34]. Cell size varies not only between cell types but also within a given cell type and, for many organisms, depends on age, sex and phase within the reproductive cycle [35][36][37]. Further, pituitary adenomas and other pituitary tumours are often associated with changes in cell size [38].…”