MEASUREMENT OF IMMUNOGLOBULIN-G LEVELS IN ADULT-RAT TESTICULAR INTERSTITIAL FLUID AND SERUM

Total immunoglobulin G (IgG) in rat testicular interstitial fluid and serum was measured by two-site enzyme-linked immunosorbent assay, whic h displayed minimal cross-reactivity with IgA or IgM. Normal adult tes ticular fluid IgG concentrations (2.67 +/- 0.98 mg/ml) were found to b e 65% of the levels found in serum. Disruption of seminiferous tubule function by experimental cryptorchidism had no effect on either testic ular or serum IgG concentrations. Castration also had no effect on ser um IgG concentrations. The effect of the Leydig cell cytotoxin, ethane dimethane sulfonate, on IgG concentrations was obscured by the observ ation that dimethyl sulfoxide (the carrier solvent) itself effectively eliminated the IgG concentration gradient across the testicular micro vasculature. In normal and cryptorchid rats, serum IgG and thymus weig hts showed no correlation with serum inhibin concentrations measured b y radioimmunoassay, although thymus weights were significantly increas ed in castrate rats. The data confirm that the permeability of the rat testis to circulating IgG is relatively high compared with other tiss ues and suggest that the testicular transendothelial transfer of IgG i s unaffected by changes in testicular activity or hormone secretion. T he high intratesticular concentration of IgG and its apparent lack of local regulation provide further evidence that the phenomenon of immun e privilege in this tissue cannot be attributed simply to restriction of immune effecters from the testicular environment. The data also ind icate that serum IgG levels in the adult male rat are not influenced i n the short-term by changes in peripheral testicular androgen levels. The direct effect of dimethyl sulfoxide on testicular endothelial perm eability requires further investigation, as this solvent is used as a carrier for nonaqueous reagents in many studies of testicular function in vivo.