Ultrastructure and morphometry of testicular Leydig cells and the interstitial components correlated with testosterone in aging rats

Abstract

The ultrastructure of testicular interstitium in young and aged adult rats was analysed using morphometric methods, and the plasma testosterone concentration was measured. With increasing age there was an augmentation in the volume of collagen fibrils in the intercellular matrix and in blood vessels. During the aging process (approximately two years) the average volume of the Leydig cell decreased from 1364 microns 3 to 637 microns 3, but the number of Leydig cells in paired testes increased from 53 x 10(6) to 113 x 10(6). The absolute volume of smooth surfaced endoplasmic reticulum (SER) per Leydig cell amounted in aged rats to 78% of that in young adult rats. The total amount of SER in paired testes increased by 62% with aging. The present analysis suggests that the ability of SER to maintain peripheral testosterone concentration decreases with age. In young adult rats the absolute volume of peroxisomes per Leydig cell correlated significantly with the concentration of testosterone in blood and also with the absolute volume of SER per Leydig cell. These results combined with ultrastructural observations of close apposition of peroxisomes and SER suggest that peroxisomes have a role in testosterone secretion by Leydig cells.

Age-related changes in the expression of 11beta-hydroxysteroid dehydrogenase type 2 in rat Leydig cells.

“…These changes are indicative for disturbed communication between seminiferous epithelium and interstitium and imply the altered testicular trophic during aging that might be responsible for dysfunction of blood-testis barrier and germ cell depletion [23]. Our findings are in concert with data for increased collagen deposition in testicular interstitium [24] and decreased tubular volume, diameter and length as well as luminal volume [25] of aged testis.…”

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

“…When specifically challenged in vitro, isolated Leydig cells of older rats of several different strains show significantly less steroidogenic response to tropic hormone stimulation than do cells from young animals [162,175,178,[181][182][183]. Only studies conducted by Kaler and Neaves [177] reported no significant differences in testosterone production by isolated Leydig cells from old rats as compared to similarly isolated cells from young controls [177].…”

“…In contrast, occurrence of Leydig cell hyperplasia as a consequence of aging has also been reported in stallions [179] and humans [141]. Other studies suggest that Leydig cells undergo atrophic changes in size [168,169,176,180] and organelle content [178] with aging. Bethea and Walker [181] provided evidence showing that aging leads to decreased Leydig cell mass, at least in testis of Fischer rats.…”

“…A number of studies indicate that the number of Leydig cells per testis is either unchanged or increased [162,[176][177][178]. In contrast, occurrence of Leydig cell hyperplasia as a consequence of aging has also been reported in stallions [179] and humans [141].…”

Numeric and volumetric changes in Leydig cells during aging of rats

“…Similarly, Wang et al 18 demonstrated that the number of LCs in old rats (up to 21 months of age) is not lower than the number of LCs in young rats, and Chen et al 19 detected no difference in the number of LCs upon stereological analysis. Thus, the decline in TT levels with age cannot be explained by loss of LCs 17,21 ; this change is the result of LCs dysfunction rather than death 7 .…”