Seminal vesicles secretions from

Seminal vesicle secretions from many species are known to harbor a large number of enzymes, many of which may simply originate from the cytoplasm of the secretory epithelial cells and play no functional roles in seminal plasma. Comprehensive accounts of the enzyme muster of vesicular secretions are provided in several treatises (1, 4, 5, 215). Only vesicular secretion enzymes that are of potential regulatory significance will be considered here. It is noteworthy that many highly active enzymes in seminal plasma originate from the epididymis and(or) the prostate gland (4, 5). 

The prostate gland and the seminal vesicles secrete the bulk of the fluid. The sources, contents and functions of the secretions from the accessory glands are given in Table 19.1. 

Mammalian vesicular secretions are rich in a limited number of species-speciflc bulk proteins alongside many other proteins (notably various enzymes) that are present in only much lower levels. Although small amounts of a few proteins that originate from blood plasma may be found in seminal vesicle secretions, the majority of proteins in these fluids are synthesized by the glands that secrete them. 

Fig. 4. Bulk secretory proteins of rat seminal vesicle secretion. The electrophoresis was conducted on 15% polyacrylamide gels in the presence of SDS and 2-mercaptoethanol (112,188,189). (a) Fresh, unfractionated vesicular secretion proteins that are soluble in the electrophoresis buffer (b) proteins in vesicular secretion that remain soluble upon extensive dilution with 150 mM NaCl, 50 mAf Tris, and 5 mM EDTA at pH 8.0. The two miyor bands going upward from the bottom of gel (b) are respectively proteins SVS-V and SVS-IV of Ostrowski c< al. (112)orSVS-F and SVS-S of Higgins eta/. (1/3). As described in the text, the lowest band (SVS-V or SVS-F) splits into two major components when the...

Figure 19.1 A diagrammatic representation of the male reproductive tract. Much of the volume of the testes consists of convoluted seminiferous tubules in which the spermatozoa form. In the interstitial tissue that surrounds the seminiferous tubules are the Leydig cells which produce and secrete androgens, oes-tradiol and the peptides inhibin and activin. The epididymis is a single but convoluted tube. Sperm from the epididymis enter the vas deferens and pass through the ejaculatory duct into the urethra, mainly at the time of ejaculation. Just at the transition of the vas deferens to ejaculatory duct, two large glands, the seminal vesicles, drain into the two vasa deferentia. Prior to joining the urethra, the ejaculatory ducts pass through the prostate gland which lies below the bladder and surrounds the upper part of the urethra, into which prostatic fluid is secreted.

The literature contains accounts of two highly basic proteins (isoelectric points 8.8 and 9.4), a powerful hemagglutinating protein, and lactoferrin in boar seminal vesicle (210-213), and of various bulk proteins (including fractions that resemble calmodulin in binding calcium tenaciously) in bull seminal plasma (214). Proteins of seminal plasmas of other mammalian species that probably originate from vesicular secretions are reviewed by Mann (4) and Mann and Lutwak-Mann (5). 

Sorbitol is secreted by boar seminal vesicle which produces rather little fructose and exhibits considerable aldose reductase but feeble sorbitol dehydrogenase activity (257). Considerable amounts of glucose and sorbitol (but not fructose) are present in seminal plasma of the stallion and jackass in which species these seminal sugars probably originate from the vesicular glands (5, 270). 

An intriguing unsolved problem from a regulatory standpoint is the mechanism of citrate accumulation and secretion by seminal vesicle and/or other male accessory glands. How citrate accumulates substan-tieilly in bone (296) and is secreted into milk by lactating mammary gland (297) is also not understood. Early studies on dog (298) and rat ventral prostate (299) disclosed that citrate is readily formed from oxaloacetate and pyruvate (or acetyl-CoA) and demonstrated many other reactions of the mitochondrial tricarboxylic acid cycle. Seminal... 

During development, a portion of the mesonephric kidney develops into two different ducts, the Wolffian and Mullerian ducts. The Wolffian duct, under the influence of testosterone, differentiates into the vas deferens, the epididymis, and the seminal vesicle. A second pair of embryonic ducts, the Mullerian ducts, develops alongside the Wolffian ducts. In males, the Mullerian ducts are suppressed due to the action of Miillerian-inhibiting substance (MIS), a hormone secreted by the testes. Maleness depends upon the secretion of testosterone from the testis, and in the absence of testosterone a male will develop a female phenotype. The SRY gene apparently activates the synthesis of MIS, which in turn assures that the Mullerian ducts will atrophy and that the mammal develops as a male. 

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