Mcl-1 is present in cultured rat Leydig cells. Immunoblot analysis of Mc1-1 in cytoplasmic protein extracts from whole, normoxic rat testis (75 μg of protein), and cytoplasmic extracts from ~1 million freshly isolated rat Leydig cells (Fresh L.C.) or Leydig cells cultured for 20 hours under either 5% or 21% oxygen. The large (Mc1-1L) and small (Mcl-1S) subunits of Mcl-1 are shown. The blot shown here was intentionally over-exposed to reveal low but detectable levels of Mcl subunits in cultured Leydig cells.