Androgen-dependent synthesis of basic secretory proteins by the rat seminal vesicle

Abstract

1. Two basic proteins were purified from secretions of rat seminal vesicles by using Sephadex G-200 chromatography and polyacrylamide-gel electrophoresis under denaturing conditions. 2. It is not certain that these two proteins are distinct species and not subunits of a larger protein, but their properties are similar. Highly basic (pI = 9.7), they migrate to the cathode at high pH and their amino acid composition shows them to be rich in basic residues and serine. Threonine and hydrophobic residues are few. Both proteins are glycoproteins and have mol.wts. of 17000 and 18500. 3. Together these two proteins account for 25-30% of the protein synthesized by the vesicles, but they are absent from other tissues. 4. Changes in androgen status of the animal markedly affect these proteins. After castration, a progressive decrease in the basic proteins is observed and the synthesis of the two proteins as measured by [35S]methionine incorporation in vitro is is decreased. Testosterone administration in vivo rapidly restores their rates of synthesis. 5. These effects on specific protein synthesis are also observed for total cellular protein, and it is suggested that testosterone acts generally on the total protein-synthetic capacity of the cell and not specifically on individual proteins. Proliferative responses in the secretory epithelium may also be involved. 6. The extreme steroid specificity of the induction process suggests that the synthesis of these basic proteins is mediated by the androgen-receptor system. 7. The biological function of these proteins is not clear, but they do not appear to be involved in the formation of the copulatory plug.

Effects of Testosterone on Sequence Complexity of Polyadenylated RNA from Rat Seminal Vesicle

“…We presume this to be the case in the seminal vesicle. The functions of the highly abundant and middle abundant sequences in the seminal vesicle of normal rats are'presently unknown but it seems reasonable to assume that the highly abundant sequence representing 40 %, of the poly(A)-rich RNA codes for one of the two major secretory proteins that accounts for up to 30% of the protein output of the glands [2,3]. In several other systems, including the steroid-hormone-sensitive chick oviduct, the highly abundant poly(A)-rich RNA fraction has been shown to contain mRNAs encoding major protein products [22,24 -271. Both homologous and heterologous hybridisation reactions show that testosterone has little effect on the highly abundant mRNA; approximately the same sequences are present and they account for a similar too [ proportion (30 -40 %) of the total mRNA irrespective of the androgen status of the rat.…”

“…Procedures not described in detail and materials not specified below will be found in earlier papers of Higgins and Burchell [3] and Higgins et al [2,81.…”

“…so that under all hormonal conditions the basic proteins account for a constant proportion of general protein synthesis and the specific activities of their mRNAs within the total mRNA population change by less than 2-fold [2,3]. Thus testosterone seems to exert no differential effects on the mRNAs for two major protein products of the seminal vesicle.…”

“…As markers for androgenic steroid hormone action, we have been studying two basic secretory proteins of the rat seminal vesicle [2]. In this tissue androgens evoke large (10-20-fold) increases in the rates of synthesis of these two proteins [2]. Regardless of the androgen status of the rat, a very close correlation exists between the rates of specific protein synthesis and the amount of mRNA present, as assayed in a cell-free translation system [3].…”

“…As markers for androgenic steroid hormone action, we have been studying two basic secretory proteins of the rat seminal vesicle [2]. In this tissue androgens evoke large (10-20-fold) increases in the rates of synthesis of these two proteins [2].…”