Microvascular permeability to IgG in the rat testis at puberty

Immunoglobulin G (IgG) spaces and permeability surface area products (PS) were calculated separately in the testis parenchyma, capsule and interstitial tissue in four age groups of rats to see if there were regional differences in microvascular permeability in the rat testis and if there were changes in PS with age. The results demonstrated a marked increase in PS to IgG at 27 days of age in the testicular interstitial tissue, whereas PS in the capsule did not show such consistent changes. Blood volumes per gram, as indicated by the 3 min IgG spaces, were considerably greater in the testicular capsule than in the interstitial tissue, although the weight of the capsule was only about one-third of the interstitial tissue weight. Maximal IgG spaces were reached at 5 h in the testicular parenchyma, but in most groups only at 20 h in the capsule. IgG was demonstrated immunohistochemically in the testicular interstitial tissue from 33 days of age onwards.