Ultrastructural analysis of a local regulation of Leydig cells in the adult monkey (Macaca fascicularis) and rat.

Peritubular Leydig cells located in interstitial areas surrounded by tubules at nearly the same stage of spermatogenesis were analysed. Low-power electron micrographs were used for measurement of cell profile area and higher magnification views provided volume density of SER, Golgi stacks, mitochondria, and lipids. In the adult monkey, no cyclic changes were found in Leydig cells in their size or in the volume density of their organelles. In the adult rat (63 days of age), a comparison limited to stage VII-VIII and stage XI-XII peritubular Leydig cells demonstrated a significantly higher SER content (P less than 0.01) in the former, but no other differences. The study of subadult rats (45 days of age) showed that the full development of spermatogenesis was required to detect significant changes in Leydig cell SER content. The present results provide morphological evidence for an intratesticular control of the Leydig cells of the rat but not for those of the monkey.