High-Resolution Autoradiography of Newly Formed Proteins in the Epididymis After Incorporation of Tritiated Amino Acids

Abstract

The synthesis and excretion of newly formed proteins in the principal cells of the head, body, and tail of the epididymis were studied by quantitative autoradiography in light and electron microscopy. Adult mice were killed from 5 min to 6 hr after intravenous injection of tritiated leucine, lysine, and arginine. The labels were taken up early and in greater amounts in the principal cells of the head. Radioactivity decreased in the cells of all three segments throughout the first hour following administration of the tracers. Thereafter, it increased in the lumen. High-resolution analysis showed successive peaks of relative concentration of the labels over the endoplasmic reticulum, Golgi apparatus, and apical plasma membrane, thus confirming that protein synthesis and excretion follow the usual pathway in the principal cells all along the epididymis. However, since a radioactivity peak occurred as early as 15 min over the apical membrane of cells in the head, it is likely that part of the endoplasmic reticulum-canalicular and poor in polysomes-is involved independently in the synthesis and rapid transport of newly formed proteins.

Ultrastructure of the mouse epididymal duct with special reference to the regional differences of the principal cells.

“…At present, the principal cells are known to secrete certain compounds including glycoprotein or protein (LEA et al, 1978;OLSON and HAMILTON, 1978;FAYE et al, 1980;MOORE, 1980). The well developed rough endoplasmic reticulum and Golgi apparatus are interpreted as cytologic features concerned with the secretory activity (HoFFER et al, 1973;JONES et al, 1979;FAIN-MAUREL et al, 1981).…”

Characterization and hormonal regulation of tissue and fluid proteins in the mouse epididymis

“…Although radioautographic studies have evidenced the pathway and kinetics of protein secretion in the various segments of the mouse epididymis (Fain-Maurel et al, 1981 ;Flickinger, 1981 ) (Brooks and Higgins, 1980) and the ram (Dacheux and Voglmayr, 1983) because of its expression in all the epididymal segments. The 30 Kd peptide most likely corresponds to the one previously designated CP 27 (27 Kd) (Flickinger etal., 1986) …”

Autoradiographic Study of Labeled Amino Acid Incorporation into Clear Cells of Mouse Epididymis

“…The increase in the relative radioactivity concentration in RER from 2 to 15 min indicated that a large part of the newly formed proteins was accumulated in this organelle, as described in principal cells of the epididymis [3]. The observed peak in labeling of the Golgi apparatus at 30 min showed movement of synthetic product via this cell compartment.…”

“…Radioactivity was measured in the trichloroaceto-soluble fraction of the plasma and in the tissues from fixed and dehydrated fragments of epididymis as described in [ 3 ] . A radioactive pulse was reached between 2 and 10 rnin in the acid-soluble fraction of the plasma, whereas a radioactivity peak occurred in the tissue from 1 0 rnin on (95% of the radioactivity was in proteins).…”