Histological Methods for Evaluation of the Testis

Histopathological evaluation provides one of the most sensitive end points for detecting the effects of' toxicants on the testis, and is used routinely in the :lSSessment of male reproductive toxicity. However, ~routine" histological methods are often inadequate for maintaining the "scnsitivity~ of this type o f evaluation. Improper fixation and inappropriate combinations or fixative: and embedding media result in unacceptable histological st:clions ( I ). TIle !.liSlor[ions inducctl by inalh:qualc methods can make (he deteCTion of differences be· tween treated and control tissues nearly impossible al all but [he highC!St dosages of a toxicant; thus, the sensitivity of the technique can be IOSlo However, Simply embedding the fixed tissues in a plastic medium such as glycol methac ryl3te medium (G!\.lA), rather than paraffin, can in some cases correct the distortions entirely. Unfortunately, there o;isl large difterences among 13OOra10· ries in the appli cation of these techniques, and thus, wide differences may be found in the interpretations of testicular pathogene.'iis. In the assessment of dlcmical toxicity in thc lestis, the rat is the most common laooratory animal tested. However, the rat testis Is difficuh to preserve: for optimal his{QlogicaJ evaluatiun because it is a fragile: organ, containing large open lymphatic spates and lacking dense connective tissue within the interstitium. Thus, if the tunica albuginea of the testis is cut, seminife.rous tubule.'i protrude like strands of soft spaghetti, and fixation after having opened the 'eslis does link to preserve the normal relati.onship bcrween tubules and interstitium. Because of these tissue·specific proble ms, there has bee n a consistent effort to impro\·e the histolOgical methods used with the ral testis ( for detailed discus· sions of these various improvements, .set" Refs. 19 ). In this chapter protocols of the most common histological methods, as weI! as some new procedures for preservation of the rat testis, arc presented. The meth· ods arc separated , first, by type of fixative; second, by routc or fixafion ; and third, by c mocdding media. 11lt= procedures section is followed by diS