Secretion of free glucose and related carbohydrates in the male accessory organs of rodents

Novel Tyrosine-Phosphorylated Post-Pyruvate Metabolic Enzyme, Dihydrolipoamide Dehydrogenase, Involved in Capacitation of Hamster Spermatozoa1

Capacitation is a process that confers fertilizing ability to spermatozoa and this critical event occurs in the development of mammalian spermatozoa during their transit through the female reproductive tract and precedes fertilization. Because spermatozoa are relatively silent in transcription and translation, posttranslational modifications perform the regulatory functions in these cells during capacitation. In this report, we identify a candidate protein, dihydrolipoamide dehydrogenase, which is a post-pyruvate metabolic enzyme, exhibiting tyrosine phosphorylation during hamster spermatozoal capacitation. This is the first report showing dihydrolipoamide dehydrogenase as a phosphoprotein. The cDNA sequence of hamster testes dihydrolipoamide dehydrogenase does not show any variation from the already reported mammalian dihydrolipoamide dehydrogenases. Downregulation of the activity of the hamster spermatozoal enzyme by its specific inhibitor, 5-methoxyindole-2-carboxylic acid, blocks acrosome reaction completely and hyperactivation partially, confirming the role of dihydrolipoamide dehydrogenase in hamster spermatozoal capacitation. We also delineate the temporal involvement of glucose and pyruvate-lactate, showing that the former is required in the earlier stages and the latter for the later stages of hamster spermatozoal capacitation. The essentiality of pyruvate-lactate during hyperactivation and acrosome reaction necessitates the involvement of the post-pyruvate-lactate enzyme, dihydrolipoamide dehydrogenase.

A comparative study of hormonal regulation of three secretory proteins (prostatic secretory protein-PSP94, probasin, and seminal vesicle secretion II) in rat lateral prostate

The rat dorsolateral prostate secretes several major known proteins, although their physiological and reproductive functions are largely undefined. In the present study we examined and compared the in vivo hormonal regulation of the messenger RNA (mRNA) expression of three major secretory proteins, including prostatic secretory protein of 94 amino acids (PSP94 or beta-microseminoprotein), probasin, and seminal vesicle secretion II (SVSII), in long-term castrated lateral prostates (LP) by in situ hybridization and semiquantitative RT-PCR. The protein levels of PSP94 in the castrated LPs were also examined by Western blotting. PSP94 is a small protein newly isolated from the rat prostate gland and demonstrates highly specific expression in the LP. The results of in situ hybridization showed that PSP94, probasin, and SVSII were highly expressed in the intact LP. The hybridization signals of probasin and PSP94 disappeared in the 60-day postcastrated LPs, whereas the signals of SVSII dropped sharply in the 14-day postcastrated LPs. Similar patterns of decreasing mRNA levels of the three proteins in the castrated LPs were observed by RT-PCR analysis. Their mRNA transcripts were restored to normal levels after replacement with testosterone. The results indicate that these secretory proteins are all under androgen regulation in the rat LP. Interestingly, we also observed that their degrees of sensitivity or responsiveness to androgen withdrawal are different. Their mRNA levels dropped in response to duration of castration in the following decreasing order: SVSII, PSP94, and probasin. Besides androgen [dihydrotestosterone (DHT)], we also examined the effects of glucocorticoid [dexamethasone (DEX)], progestin [medroxyprogesterone acetate (MPA)], and zinc on their gene expressions in castrated LPs. We observed that the mRNA transcripts of both PSP94 and probasin were increased after treatments with DHT, DEX, and MPA, suggesting that these two proteins could also be regulated by glucocorticoid and progestin. In contrast with probasin, PSP94 and SVSII were not induced by ZnSO4 treatment. On the other hand, SVSII expression was only increased significantly by DHT and moderately by MPA, but not by DEX, suggesting that SVSII is under strict control by androgen.

PSP94 (or beta-microseminoprotein) is a secretory protein specifically expressed and synthesized in the lateral lobe of the rat prostate

BACKGROUND

Prostatic secretory protein of 94 amino acids (PSP94), also called beta-microseminoprotein, is a small, nonglycosylated protein, rich in cysteine residues. It was first isolated as a major protein from human seminal plasma. Subsequently, its homologous proteins were identified, and their cDNAs or genes have been cloned in primates, pigs, and rodents.

METHODS

The present study investigated the expression pattern of PSP94 in the normal Noble rat prostate gland by nonradioactive in situ hybridization, Northern blotting, RT-PCR, Western blotting, and immunohistochemistry. Its expression in the mouse prostate gland was also examined by in situ hybridization.

RESULTS

The results of in situ hybridization, and Northern and Western blot analyses, showed that the expression of rat PSP94 was prostate-specific. It was highly expressed in the lateral prostatic lobe, moderate in the dorsal lobe, weak in the coagulating gland, and negative in the ventral lobe and seminal vesicle. Its specific expression in the rat prostate gland was further confirmed by RT-PCR analysis of prostatic and nonprostatic organ tissues. Its mRNA transcripts were not detected in the urinary, digestive, and respiratory tracts, male and female reproductive organs, muscles, brain, and kidney. Its molecular mass was estimated to be 14.5 kDa by Western blotting. Similar prostate-specific expression of PSP94 was also observed by in situ hybridization in the lateral lobe, but not in the dorsal and ventral lobe, of the mouse prostate gland.

CONCLUSIONS

Rat PSP94 is a major secretory protein highly expressed and synthesized by the lateral lobe of both rat and mouse prostate glands, and moderately expressed in the dorsal lobe of the rat prostate gland.

Comparative study of glycoconjugates of the rat prostatic lobes by lectin histochemistry

BACKGROUND

The rat prostate gland is composed of several distinct lobes: the ventral, lateral, dorsal, and anterior (also called the coagulating gland). Each prostatic lobe is different in its morphology, secretions, and response to hormones.

METHODS

The present study characterized and compared the expression of glycoconjugates in three different lobes (ventral, lateral, and dorsal) of the Noble rat prostate gland by lectin histochemistry, using a battery of 30 different lectins.

RESULTS

The results indicate that different prostatic lobes elaborate and secrete different glycoconjugates. The dorsal prostatic epithelium secretes mainly in an apocrine mode, as characterized by the presence of apical cytoplasmic blebs which are absent in the other two lobes, though merocrine secretion is also suggested. These cytoplasmic blebs were rich in Man, GlcNAc, Gal/GalNac, Fuc, NeuAc(alpha2,6)Gal, and oligosaccharides. Two types of cytoplasmic belbs were also identified according to their lectin bindings: blebs stained by S-Con A, LCA, PWA, UEA-II, RCA-I, DBA, ECA, WFA, Jacalin, MPA, SJA, LTA, UEA-I, PHA-E, and PHA-L, and some blebs stained by S-WGA, SBA, HAA, HPA, VAA, BPA, MAA, and SNA. The lectins, which reacted with the second type of blebs, also revealed some cytoplasmic granules in the dorsal prostatic epithelial cells. The epithelium of the lateral prostate showed weak or negative reactions to lectins, suggesting that it may express fewer glycoconjugates as compared to the other two lobes. The epithelial Golgi region of the ventral prostate is the most developed among the three lobes, and contained abundant GlcNAc, alpha/beta-GalNAc, and NeuAc(alpha2,6)Gal residues, as shown by its intense reactions to S-WGA, DBA, SBA, HAA, HPA, WFA, and SNA. GS-I-B4 reacted specifically with the basal epithelial cells in all three lobes, indicating that glycoconjugates with terminal alpha-Gal/GalNAc were commonly expressed in these basal cells. The basal cells in ventral prostate might express more complex glycoconjugates, as they were also stained by PWA, RCA-I, ECA, and PHA-L, in addition to GS-I-B4, suggesting that these basal cells contained more Gal(beta1,4)GlcNAc and Gal(beta1,4)GlcNAc(alpha1,2)Man residues. GS-I-B4 and PHA-L also demonstrated a differential staining of the stromal smooth muscles and their associated extracellular matrix in the three prostatic lobes, suggesting that these structural components in different prostatic lobes were different in their complex oligosaccharide contents, which probably has an influence on the epithelial-stromal interaction in the prostate.

CONCLUSIONS

In summary, the present study has established for the first time the expression patterns of glycoconjugates in the three lobes of the Noble rat prostate gland and suggests that certain lectins are useful as histochemical markers for the three individual prostatic lobes.

Characterization of glycoconjugates of guinea pig seminal vesicle by lectin histochemistry

In the present study, the expression of glycoconjugates in the guinea pig seminal vesicle was localized and partially characterized by lectin histochemistry using a battery of 30 different lectins specific for different carbohydrate residues. The results indicate that the glandular epithelium of the guinea pig seminal vesicle exhibits complex glycoconjugates rich in Man, beta-GlcNAc, beta-Gal, alpha/beta-GalNAc, Fuc and complex NeuAc(alpha2,6)Gal/GalNAc residues, as shown by its positive reactions to most lectins used. The Golgi region of the luminal secretory epithelial cells expresses a complex glycoconjugate pattern, as shown by its strong reactions to Man-(PSA, GNA), beta-GlcNAc-(S-WGA, PWA, DSA, UDA), beta-Gal-(RCA-I and -II), alpha/beta-GalNAc-(SBA, Jac, VVA, BPA) and complex NeuAc-(SNA) specific lectins, indicating that the secretory epithelial cells are active in glycosylation and secretion process. It was also shown in the present study that the basal and luminal epithelial cells are different in their glycoconjugates. The basal epithelial cells are rich in NeuAc(alpha2,3)Gal residues as they are stained specifically by MAA. The fibroblasts in the epithelial-smooth muscle interface and the smooth muscle cells close to the glandular epithelium are shown to express more glycoconjugates as they are stained intensely by GS-I-B4, GS-II and SBA. However, their role in the epithelial-stromal interaction in the seminal vesicle remains to be elucidated. In summary, the present study reports for the first time on the lectin binding patterns of the guinea pig seminal vesicle, and the results show that the seminal vesicle epithelium elaborates and secretes glycoconjugates in a complex pattern. Some of the lectins might be useful as histochemical markers for the secretory activity and specific structural components in the guinea pig seminal vesicle.

Contents of fructose, citric acid, acid phosphatase, proteins and electrolytes in secretions of the accessory sex glands of the male golden hamster

Secretions were collected from the ampullary gland, dorsolateral prostate, ventral prostate, coagulating glands and seminal vesicles of male golden hamsters aged 15-20 weeks. The concentrations of total protein, citric acid, fructose, acid phosphatase, chloride, sodium, potassium, calcium, magnesium and zinc were determined. The ampullary gland secreted predominantly citric acid, sodium and acid phosphatase. Zinc was secreted only by the prostatic complex, with the largest quantity coming from the coagulating gland. The highest concentrations of potassium, calcium and magnesium were found in secretions of the ventral prostate. The coagulating gland and dorsolateral prostate were the principal contributors to total protein. The hamster appears to be more related to the mouse than to the rat in terms of the secretory functions of its accessory sex glands.

Biochemistry of male accessory organs of conilurine rodents

The plains mouse has large seminal vesicles, coagulating glands, and dorsal and ventral prostates, whereas in the hopping mouse the only large accessory sex gland is the ventral prostate. Fructose concentration was found to be high in the coagulating glands and dorsal prostate of the plains mouse, but low in all other glands of both species; low concentrations of glucose were found in all glands. Citric acid concentration was high in the dorsal prostate of the plains mouse and ventral prostate of the hopping mouse. Acid and alkaline phosphatase activities were low in all glands of both species. In castrated hopping mice, enlargement of vestigial glands could not be induced with high doses of exogenous testosterone, although there was increased secretory activity of the seminal vesicle epithelial cells.