The postnatal development of the junctional complexes of hamster Sertoli cells as revealed by HRP and freeze-fracture.

The development of the Sertoli cells occluding junctions was investigated in testes from 5-, 10-, 15-, 20- and 30-day-old hamsters after intravascular administration of horseradish peroxidase (HRP) and by freeze-fracture. Up to the 15th day, HRP could be detected in the interstitial spaces and the central area of testicular cords. On day 20, the tracer reached the lumen of some tubules but in others it was retained at the periphery of the seminiferous epithelium, thus suggesting an asynchronous formation of the blood-testis barrier along the length of the tubules. Gap junctions associated with short rows of particles were found on freeze-fracture replicas from 5-day-old animals. Later on, a decrease in the frequency of gap junctions and a corresponding increase in the number of tight junctions was observed. Beyond the 20th day, tight junctions became morphologically and physiologically similar to those of mature animals, indicating establishment of the blood-testis barrier.