Fig. 4. MAP is a major protein constituent of the luminal gonad-duct fluid. Representative SDS-gel electrophoresis (A) and western blot (B) revealed with anti-MAP antibodies. The protein loading for each lane is indicated. Lane 1, extract from the total gonad/mantle (15 µg). Lanes 2 and 3, cell-free fraction obtained from the lumen of the longitudinal gonadal duct (LGD) (4 µg per lane). Lanes 4 and 5, cell-free fraction obtained from the lumen of the transversal gonadal ducts (TGDs) (4 µg per lane). Lane 6, sperm cells obtained from the lumen of the TGDs (15 µg). Note that the intensity of MAP immunostaining is much higher in the luminal fluid than in sperm and total gonad extract. The positions of marker proteins (kDa) are shown.