TOPOGRAPHICAL UPTAKE OF BLOOD-BORNE HORSERADISH-PEROXIDASE (HRP) IN THE MURINE TESTIS AT THE LIGHT-MICROSCOPIC LEVEL

Light microscopical studies on the uptake of blood-borne horseradish p eroxidase (HRP) in large areas of the testis have been scarce because of the difficulty of staining HRP in testes with well-preserved morpho logy. However, observation of exogenous HRP in all areas of the testis enables detection of regional tissue injury induced by toxic chemical s or immunization. In the present study, the localization of blood-bor ne HRP in the murine testis was investigated light microscopically usi ng plastic-embedded testes and post-embedding histochemical methods. M ice were injected intravenously with HRP, and then perfused with 2.5% glutaraldehyde and 3% paraformaldehyde in 0.1 M phosphate buffer. The fixed testes were immediately removed, dehydrated, and then embedded i n plastic without cutting them into small pieces. The prepared section s treated by the diaminobenzidine method exhibited intense HRP activit y with well-preserved testis morphology. It was noted that many inters titial macrophages had endocytosed HRP. In particular, HRP-endocytosin g macrophages were concentrated around the tubuli recti. The testicula r capsule, containing many lymphatic capillaries and vessels, was also loaded with HRP. In the subcapsular interstitium, free HRP in the lym ph space accumulated, but the staining intensity was weak compared to that in testicular macrophages. No HRP infiltration into the lumen of the seminiferous tubules was observed at the light microscope level; h owever, HRP staining was detected in tubular walls and epithelial cell s lining the rete testis and tubuli recti, indicating that these regio ns are permeable to HRP.