Cellular interrelationships in the fetal rabbit testis

The types and patterns of arrangement of membrane interrelationships in the fetal rabbit testis were studied, using coordinated freeze-fracture, lanthanum tracer and standard transmission electron microscopic techniques. The testicular cords contain a mixture of large spherical germ cells and oval to elongated Sertoli cells. Desmosomes are present between germ cells and Sertoli cells and between adjacent Sertoli cells. Tight junctional specializations of the type found between Sertoli cells in the adult are not seen. In freeze-fracture replicas, short strands of particles of two different size populations are found on the surfaces of Sertoli cells. Similar short strands of particles are present on the membranes of peritubular myoid cells. In lanthanum preparations, the tracer passes freely between peritubular cells and through intercellular spaces within the seminiferous cords, indicating lack of a barrier to its passage throughout the testicular tissue. Prominent macular gap junctions similar to those found between adult Leydig cells are readily observed on the surfaces of fetal Leydig cells. The presence of gap junctions in the fetal testis may be important in coordinating the active testosterone production which occurs during this period of development.