Testicular involution following optic enucleation: the Leydig cell.

The testes of Syrian hamsters underwent pronounced involution within six weeks after blinding. The seminiferous tubules were devoid of all stages of spermatid development and mature spermatozoa were absent from the tubule lumina. The diameter of of the Leydig cells was 25% less than that of controls. Examination with the electron microscope revealed thick bundles of collagen fibrils interspersed between Leydig cells and surrounding Leydig cells in the blinded hamsters. The Leydig cell nuclei were shrunken and highly infolded. Lipid droplets that were often seen in normal Leydig cells were absent in the involuting Leydig cells. The size of the Golgi complex and the amount of smooth endoplasmic reticulum were reduced. Results of the present experiment confirm that inactivity of the Leydig cells is the reason for the decline in serum testosterone levels in blinded hamsters.