Abstract
In the present study the postnatal development of the testis of 67 male cats was examined. The youngest cats were neonatal, the oldest ones had been castrated at the age of 12 months. Apart from investigating the morphology by light- and electron-microscopic methods, the growth of some of the tissues´ components (for example the area of the seminiferous tubules) were recorded morphometrically. In addition, the concentration of testosterone in the animals´ plasma was measured. These investigations give an overview of the structures of the cats´ testis at different ages and point out influences of parts of the organ depend on each other during their development. This is supported by comparison of the morphology, the morphometric parameters and the concentration of testosterone in the plasma.
At birth, moderately coiled, solid germinal cords can be found in the testis of the cat. They have a single-layered epithelium, which contains mainly SERTOLI cells and only a few germinal cells. The intertubular tissue is loose, containing LEYDIG cells. These cells also occur in great number underneath and in between the tunica albuginea, where they are named "heterotopic LEYDIG cells". From the age of 4 months on the formation of a lumen starts in the peripheral situated seminiferous tubules and from 4? months on they build a stratified germinal epithelium, leading on spermatogenesis. The germinal cord in the centre remain solid for a longer time and spermatogenesis starts later. After 7-8 months spermatogenesis covers all tubules. All quantitative parameters (testicular weight, area of tubules, area of parenchyma, etc.) except the testosterone concentration in the plasma increase abruptly in the 20th week of life.
SERTOLI cells in neonatal cats already have a high level of maturity. From the 4th month on they play a leading role in forming the tubular lumen. Two kinds of SERTOLI cells can be distinguished: the dark type shows features that indicate a high metabolic activity, but they also seem to degenerate more often. The light type occurs much more often and shows characteristics also described in other species. The blood-testis barrier was demonstrated by fixation, containing lanthanum nitrate. The barrier is established from the 4th month on and apart from SERTOLI cells it is also maintained by testicular blood vessels, which are not permeable to lanthanum nitrate.
The myofibroblasts of the lamina limitans contain contractile filaments from the 2nd month of life on and they are surrounded by an incomplete basement membrane.
From the beginning of the investigated period the intertubular as well as the heterotopic LEYDIG cells show all characteristics of steroid hormone production. In the blood plasma testosterone is first detectable in the 10th week of life and the concentration does not increases until the 26th week, which seems inconsistent with other quantitative and qualitative features.
The particularities of the cats testis and its development are part of the discussion. In addition the discrepancy between the morphological degree of maturation of LEYDIG cells and of the parenchyma and the testosterone levels in plasma as well as the regional differences within the testis in connection with the heterotopic LEYDIG cells, typical of the cat, are discussed. |