Specific protein synthesis in isolated epithelium of guinea-pig seminal vesicle. General features

Abstract

Four intrinsic soluble proteins are synthesized and secreted by sexually mature guinea-pig seminal-vesicle mucosa, which comprises a monolayer of a homogeneous columnar epithelial cell. All 4 proteins can be extracted readily in 154 mM-NaCl from the organ''s luminal constituents in which they are present in high concentration. They are referred to as proteins 1, 2, 3 and 4 in order of their elution during DEAE-cellulose column chromatography. Specific primary antibodies were harvested from goats that were inoculated with the purified vesicular proteins; secondary antibodies were obtained from a donkey inoculated with goat .gamma.-globulins. Double-antibody-immunoprecipitation techniques were developed to precipitate the vesicular proteins. Proteins newly synthesized from 14C-labeled amino acids were precipitated and the incorporated radioactivity assessed. Isolated seminal-vesicle mucosa, incubated in only a buffered salt solution containing glucose, readily synthesized the soluble secreted proteins from added [14C]lysine plus [14C]-glycine, [14C]histidine plus [14C]glutamate, [14C]glutamine alone and [14C]arginine alone. The rates of incorporation (d.p.m.[disintegration per minute]/mg of total soluble protein) of labeled lysine and glycine and of labeled arginine were linear with time over 180 min. With the other labeled precursors, rates diminished between 60 and 180 min. Labeled protein was detected after only 10-15 min of incubation. Only 4-9% of the newly synthesized protein remained associated with the mucosa; the remainder was found in the cell-free incubation medium. The isolated seminal-vesicle mucosal preparation will provide a unique opportunity to study the synthesis and secretion of abundant cell-specific proteins by this androgen-dependent tissue.