Synthesis, transport and secretion of protein in the initial segment of the mouse epididymis as studied by electron microscope radioautography.

Abstract

Adult male mice were administered l3Hl-leucine and samples of the initial segment of the epididymis were prepared for light and electron microscope radioautography after intervals ranging from 10 min-12 h. Light microscope radioautography revealed labeling of the principal cells of the epididymal epithelium and radioactivityappeared in the epididymal lumen 2 h afterinjectionof (3H1 -leucine.Luminal labelingwas not abolished by prior ligationof the ductuli efferentes. Analysisof electronmicroscope radioautographs of principalcellsdemonstrated successivepeaks in the percent of grainsand in relativegrain concentrations over the rough endoplasmic reticulum at 10 mm and the Golgi apparatus at 1 h after injection of precursor. A high proportion of grains was associated with the “smooth” endoplasmic reticulum at allintervals,but itsrelativegrain concentration did not reach the values attained by the rough endoplasmic reticulum and Golgi apparatus. Luminal labeling was associated mainly with material lying between spermatozoa. The resultsindicatethat the rough endoplasmic reticulum and the Golgi apparatus of the principal cells were involved in synthesis and transport of protein. Approximately 2 h were requiredforintracellular events in epididymal protein secretion. Suggestions as to the role of the smooth endoplasmic reticulum are presented. The mode of release of secretory protein remains uncertain.