Decreased in Vitro Testosterone Production by Isolated Ley dig Cells from Uremic Rats

We compared in vivo and in vitro Leydig cell function in chronically uremic adult male rats (4 weeks after 5/ 6 nephrectomy) with that in healthy controls. Levels of serum urea nitrogen (SUN) were higher in nephrectomized animals than in controls [62 ± 6 vs. 13 ± 1 mg 5/dl (mean ± SEM), P < 0.01]; serum testosterone (T) levels were lower (135 ± 25 vs. 440 ± 64 ng 5/dl; P < 0.01). Serum LH was significantly lower in the uremic rats, being at or below the limits of detection of the assay. After in vitro exposure to various concentrations of hCG for 120 min, the mean T responses of Leydig cells from uremic rats were diminished at each dose of hCG employed (P < 0.01). Both basal levels and peak responses were reduced by approximately 50%. The apparent potency of hCG, as judged by T response, was reduced in Leydig cells from uremic rats to 3% of that in cells from normals, but showed partial recovery with increased duration of in vitro exposure to hCG, uremic cells having relative potencies of 5% (95% confiden...