Compared to other vertebrates, Squalus and related species have a unique combination of features: a) a “cystic” mode of spermatogenesis, in which a single germinal clone and a second clonal population of stage-synchronized Sertoli cells form a follicle-like unit (spermatocyst); b) the arrangement of spermatocysts in maturational order across the diameter of the testis, resulting in a readily visible zonation in testicular cross sections; and c) reliance mainly or exclusively on Sertoli cells for somatic cell support of spermatogenesis, differentiated Leydig cells being absent at this phyletic level (see Fig. 1). The present study was designed to test the utility of the shark testis model for stage-by-stage analysis of toxicant accumulation and effect, using cadmium (Cd) as an illustrative toxicant. ventolin 100 mcg
Cd is rare in nature and has no known biological utility. Although Cd seldom reaches toxic concentrations in the environment, levels have progressively increased as a consequence of industrial pollution attributed to electroplating, stabilizers, pigments, plastics, semiconductors, and batteries. Moreover, the long half-life (10-30 yr in human kidney) and bioaccumulation and biomagnification of Cd in plants and animals increase the potential for human exposure and effect. The rodent testis is exquisitely sensitive to Cd toxicity, and permanent or temporary sterility is induced at Cd doses below those that have adverse effects on the vasculature. The primary goal of the present study was to define the intrates-ticular distribution of radiolabeled and radioinert Cd as a function of developmental stage. Because metallothionein (MT) is a Cd-inducible, Cd-binding component, we used a standard Cd-binding assay to measure MT-like protein as a possible marker of tissue Cd accumulation and effect.