IDENTIFICATION OF 2 TYPES OF BETA-COP VESICLES IN THE GOLGI-COMPLEX OF RAT SPERMATIDS

In the present study, immunoelectron microscopy was used to characteri ze two types of coated vesicles at the trans Golgi reticulum (TGR) of rat early spermatids. Most of the coated vesicles and buds had a 18.4 +/- 0.5 nm thick electron-dense coat. The size of the vesicles without the coat was 102.6 +/- 3.6 nm. This coat reacted with antibodies agai nst clathrin. Immunolabeling for clathrin was almost restricted to the trans Golgi area (86% of the total labeling in the Golgi complex). In addition, we found a homogeneous population of small vesicles and bud s bearing a similar to 10 nm thick coat which reacted with antibodies against beta-COP. beta-COP-immunoreactive vesicles were detected at th e cis side (32 %), lateral rims (27 %) and trans face (40 %) of the Go lgi complex. The diameters of beta-COP-immunoreactive vesicles at the TGR and cis Golgi side were 53.9 +/- 1.3 and 42.1 +/- 1.1 nm, respecti vely. Cis Golgi elements were identified by using antibodies against m arkers of the Golgi intermediate compartment p 58, p 53 and Rab 2. Som e beta-COP labeling was also found at the acrosomal membrane and assoc iated buds. These results indicate that the TGR of early spermatids co ntains COP-coated vesicles which are different to those found at the c is Golgi side.