Sexually Dimorphic Effects of Aging on Rat Somatotroph Cells. An Immunohistochemical and Ultrastructural Study.

Abstract

Aging produces alterations in certain functions of the hypothalamo-pituitary axis that result in sexually dimorphic changes in the somatotrophs. Since quantitative morphological data on these age-associated alterations are scarce, we prompted to make a morphometric immunohistochemical assessment as well as undertake an ultrastructural study of the somatotrophic (GH) cell population in male and female rats of different ages. Young (3-month-old), old (20-month-old), and senescent (29-month-old) Sprague-Dawley rats of both sexes were sacrificed by rapid decapitation, their pituitaries immediately dissected out, and processed for both immunohistochemistry and electron microscopy. Analysis of different morphometric parameters revealed that surface density, volume density, and cell density significantly decreased in old and senescent rats as compared to young animals, with this reduction being clearly more marked in females. Both the GH-cell area and perimeter decreased in senescent male rats, while these parameters increased in senescent females. The ultrastructure of the GH cells from old and senescent animals of both sexes evinced changes suggestive of an immature state, with some somatotrophs having the appearance of cells undergoing an involutive process. We conclude that aging has a differential impact on the GH cells of male and female rats with respect to the immunohistochemical and ultrastructural features of that cell population.

Immunohistochemical and Ultrastructural Study of Pituitary Folliculostellate Cells during Aging in Rats

“…Despite our being able to demonstrate that in the rat pituitary, aging affects not only the different types of hormone-secreting cells but also the FS cells, marked ultrastructural changes in this population similar to those described for some endocrine cells in rats [Có nsole et al, 1998;Jurado et al, 1998] were not depicted in the present study; only moderate, although frequent modifications appeared.…”

“…5). The remarkable changes appearing with age in the different types of endocrine cells that we described previously [Có nsole et al, 1998;Jurado et al, 1998] were also observed here ( fig. 3).…”

“…These changes have been revealed through quantitative immunohistochemical studies [Takahashi and Kawashima, 1983;Có nsole et al, 1994Có nsole et al, , 1995Có nsole et al, , 1997 as well as by means of electron-microscopical observations [Có nsole et al, 1998;Jurado et al, 1998]. Little is known, however, about the effect of aging on the pituitary FS cells, in spite of the multiple important functions that have been reported for this cell population.…”

“…Nishioka et al [1991] found numerous FS cells bordering adenoma and nonadenoma pituitary lesions, suggesting an association between the FS cell population and glial nerve tissue. At the ultrastructural level, conspicuous changes have been described for some types of endocrine cells in the pituitary of old rats [Có nsole et al, 1998;Jurado et al, 1998]. The presence of a system of interrelated follicles in the adenohypophysis would indicate the occurrence of a functional syncytium with signal transmission through gap junctions [Soji et al, 1992].…”

“…Although quantitative immunohistochemical studies have been done on the hormone-secreting cells of the anterior pituitary of old rats [Takahashi and Kawashima, 1983;Có nsole et al, 1993Có nsole et al, , 1994Có nsole et al, , 1995Có nsole et al, , 1997Jurado et al 1998], no attempts have been made to quantitate the progressive changes that occur in the FS cells of rats along with the aging process in general, or at an advanced stage of senescence in particular. The aim of the work reported here was thus to carry out a quantitative immunohistochemical study of the FS cells in male and female rats during aging, and to correlate the findings with possible changes at the ultrastructural level.…”