Phospholipases A2 in the reproductive system of the bull.

1. Phospholipase A2 activities were studied in the reproductive organs, seminal plasma and spermatozoa of adult bulls. 2. Phosphatidylethanolamine and phosphatidylcholine with 14C-labelled linoleic (lino-PE, lino-PC) or arachidonic acid (ara-PE, ara-PC) at sn-2 position as well as a fluorescent derivative (4-pyrenylbutyric acid) of phosphatidylcholine (PPC) were used as substrates. 3. The radioactive substrates were hydrolysed most strongly by homogenates of the prostate and Cowper's gland, but also seminal vesicle and its secretory fluid, seminal plasma and ejaculated spermatozoa contained hydrolytic activity. The fluorescence substrate was most strongly hydrolysed by homogenates of ampulla and seminal vesicle as well as its secretory fluid, seminal plasma and ejaculated spermatozoa. 4. Seminal plasma and seminal vesicle fluid contained a Ca2(+)-independent enzyme (enzyme I), which hydrolysed only PPC, while another Ca2(+)-dependent enzyme (enzyme II) hydrolysed only the radioactive substrates. 5. Both enzymes were purified from the seminal vesicle fluid and their biochemical properties were analysed. In SDS-PAGE enzyme I preparation resulted in two major bands with molecular weights of 16,000 and 60,000 in equal quantities and minor band at 15,000. The binding of the enzyme I to Con A-Sepharose indicated that it is a glycoprotein and it had multiple pI-values from 3.75 to 5.0. Enzyme II gave in SDS-PAGE two closely located bands with molecular weights of about 15,000 and 16,000 (major band). Isoelectric focusing showed one band at pI 4.7. Both enzymes appear to bind to spermatozoa at ejaculation but their function remains to be shown.

Incorporation of selenium-75 into seminal plasma and spermatozoa of the bull.

75Se was given intravenously into 5 bulls. Multiple blood and semen samples were taken and during slaughter 5, 10, 15, 20 and 80 days later samples of various reproductive and other organs were collected. After injection, 75Se in blood reached a peak at 6 h followed by a rapid decline. The label was mainly found in serum with very low levels in erythrocytes. Initially the serum 75Se was bound to a macromolecule with a mw of 80 kDa, but later a larger molecule (100 kDa) was observed. In semen 75Se was first mainly found in seminal plasma, where a plateau level was reached at 5 d followed by a gradual decline after 12 d. The total semen level, however, increased after 14 d and this increase was due to a rapid appearance of the label in spermatozoa. The sperm 75Se level reached a plateau at 20 d and remained high until 40 days, after which a gradual decline ensued. The seminal plasma 75Se eluted in gel filtration coincident with glutathione peroxidase. The highest levels of 75Se were found in the kidney followed by seminal vesicles and testicles. The seminal vesicle secretion was particularly rich in 75Se and its fractionation resembled that of the seminal plasma. 75Se appeared in the epididymal caput within 5 days and passed through the epididymis in 20 days. It is concluded that 75Se is actively incorporated in the bull seminal vesicles into GSH-Px, while in the testis it is incorporated into a structural sperm protein during spermatogenesis.

Hydrolases from bovine seminal vesicle, prostate and Cowper's gland.

The bovine seminal plasma is formed mainly by secretions of epididymis and the glandular epithelia in ampulla, seminal vesicles, prostate and Cowper's glands. The contribution of each organ to the hydrolytic enzyme activities (glycosidases, exopeptidases, phospholipases) of the bull seminal plasma has been analyzed and is reviewed in this paper with special emphasis on the role of the accessory glands. Seminal vesicles seem to have a major role in the secretion of seminal plasma acid alpha-glucosidase, acid alpha-mannosidase and beta-N-acetylhexosaminidase, aminopeptidase A, dipeptidyl peptidase II and IV and gamma-glutamyl transpeptidase as well as Ca(2+)-dependent and Ca(2+)-independent phospholipases A2 with distinct substrate specificities, a choline-specific phospholipase C and a Co2+ (Mn2+)-activated sphingomyelinase. The enzyme pattern in the ampulla closely resembled that of the seminal vesicles and obviously contributes to the seminal plasma level of these hydrolases. The bull prostate and Cowper's glands contained a strong Ca(2+)-dependent phospholipase A2 activity. However, these glands may not contribute to the seminal plasma PLA2 activity. At ejaculation the epididymal spermatozoa are exposed to these enzymes. They may have a specific affinity to sugar, peptide or phospholipid residues at distinct sites of the sperm surface. These enzymes may also participate in the digestion of various other semen components to create a suitable milieu for the emitted spermatozoa.

Gamma-glutamyl transpeptidase in rat epididymis: effects of castration, hemicastration and efferent duct ligation.

Gamma-Glutamyl transpeptidase (gamma-GT) was studied histochemically and biochemically in the rat epididymis after castration with or without testosterone treatment, or after hemicastration and ligation of the efferent ducts. There was a strong reaction to gamma-GT in the apical part of the epithelium in the caput epididymis, while in the corpus and cauda the reaction was confined mainly to the luminal contents. Castration caused a marked decline in epithelial gamma-GT activity within 10 days. Subsequent testosterone treatment (1 mg/day for 10 days) restored gamma-GT activity in the apical surface and lumen. After hemicastration of adult rats, and after hemicastration or ligation of the efferent ducts in immature 28-day-old rats, a small but significant (P less than 0.001) decrease was observed in gamma-GT activity in the epididymal caput compared to controls. The quantities of six other enzymes (beta-N-acetylglucosaminidase, beta-galactosidase, angiotensin-converting enzyme, alanyl amino-peptidase, dipeptidyl peptidase IV, acid phosphatase) also displayed significant changes after castration and restoration of activities by testosterone treatment. However, their distribution in the caput and cauda epididymis was more even than that of gamma-GT, and the changes after castration were less drastic. It is concluded that gamma-GT is a highly sensitive androgen-dependent secretory marker in the caput epididymis and may have an important function in sperm maturation.

Distribution of gamma-glutamyl transpeptidase in the mouse epididymis and its response to acivicin.

gamma-Glutamyl transpeptidase (gamma-GT), its substrate (GSH) and hydrolytic product (L-glutamic acid) were measured biochemically in mouse reproductive tissues. The epididymal caput and seminal vesicles showed the highest specific activities of gamma-GT, while GSH and L-glutamic acid were widely distributed in all tissues. Histochemically, gamma-GT displayed a strong apical and supranuclear reaction and a moderate basal activity in the ductuli efferents, a weak luminal reaction in the first, a moderate apical reaction in the second and a strong apical and supranuclear reaction in the third segment of the epididymal caput. In the epididymal corpus and cauda, the gamma-GT reaction was confined to the tubular lumina but an apical reaction was also present in the cauda. The daily administration of acivicin (12 mg/kg body weight), an irreversible inhibitor of gamma-GT, for 14 days resulted in a 60% suppression of the enzyme activity in the epididymal caput, while the gamma-GT inhibition in the kidney was greater than 95%. The treatment caused no change in the activity of alanyl aminopeptidase. Histochemically, the basal and supranuclear gamma-GT activities in the ductuli efferents and the third epididymal segment were suppressed, but the apical reactions were maintained. The in-vivo suppression of epididymal gamma-GT activity may have implications in the control of post-testicular sperm maturation.

Semen selenium content and sperm mitochondrial volume in human and some animal species.

Selenium (Se) and glutathione peroxidase (GSH-Px) were determined from the seminal plasma samples and spermatozoa of human and four different animal species. The human sperm Se concentration was 1.8 +/- 0.8 micrograms/g dry weight, which was about half of that in the bull. Abnormal sperm morphology and motility correlated with low sperm Se content. The volume of sperm mitochondrial sheath in human, bull and stallion was measured using transmission electron microscopy. In these species the sperm Se content was highly correlated with the volume of mitochondria. Among the five species studied, the seminal plasma level of Se was lowest in human male and stallion, while the highest levels were encountered in the bull. No correlation was obtained between human semen quality and seminal plasma Se concentration. The seminal plasma GSH-Px activity was low in man and ram, absent in boar and stallion but very high in the bull. The amount of structural sperm Se as well as seminal plasma Se and GSH-Px activity appears to be highly variable in different species.

Human seminal plasma cadmium: comparison with fertility and smoking habits.

Cadmium, selenium and zinc were determined in seminal plasma and serum of 64 men by atomic absorption spectrometry (AAS). The mean (+/- SD) cadmium concentrations in seminal plasma and serum were 0.22 +/- 0.22 micrograms and 0.28 +/- 0.10 micrograms, respectively, but they did not correlate with each other. Smokers (n = 31) had significantly (p less than 0.01) higher serum cadmium concentrations than non-smokers (n = 31). Also seminal plasma cadmium in smokers was elevated, but a significant difference to non-smokers was only found if more than 20 cigarettes were consumed daily. No differences were found in semen quality and fertility between smokers and non-smokers. The seminal plasma cadmium had no correlation to selenium or zinc which, however, displayed a positive correlation (r = 0.852, p less than 0.001) to each other. It is concluded that smoking increases the exposure to cadmium. Although no obvious reproductive suppression was observed, heavy smoking may possibly enhance toxic effects in men under other detrimental exposures.

PIP: Cadmium, selenium, and zinc were determined in seminal plasma and serum of 64 men by atomic absorption spectrometry (AAS). The mean (+or- SD) cadmium concentrations in seminal plasma and serum were 0.22 +or- 0.22 mcg and 0.28 +or- 0.10 mcg, respectively, but they did not correlate with each other. Smokers (n=31) had significantly (p0.01) higher serum cadmium concentrations than nonsmokers (n=31). Also, seminal plasma cadmium in smokers was elevated, but a significant difference to nonsmokers was only found if 20 cigarettes were consumed daily. No differences were found in semen quality and fertility between smokers and nonsmokers. The seminal plasma cadmium had no correlation to selenium or zinc which, however, displayed a positive correlation (r=0.852, p 0.001) to each other. It is concluded that smoking increases the exposure to cadmium. Although no obvious reproductive suppression was observed, heavy smoking may possible enhance toxic effects in men under other detrimental exposures. (author's)

Purification and characterization of phosphatidylinositol-specific phospholipase C from bovine spermatozoa.

1. The distribution of phosphatidylinositol3, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate hydrolysis or phosphatidylinositol-specific phospholipase C (PI-PLC), activity in the bull reproductive system showed the highest specific activity in the isolated spermatozoa (SZ) followed by testis and different epididymal segments. Both the head and tail fractions of SZ were active. 2. The optimal solubilization of the enzyme from SZ was obtained with 0.2% Triton X-100 or at 0.05% detergent concentration when combined with a 60 sec sonication. The sucrose gradient centrifugation showed that PI-PLC was enriched in membrane fraction distinct from mitochondria and acrosomes. 3. The enzyme was purified by ammonium sulphate precipitation and fractionations by hydrophobic interaction chromatography, gel filtration, Con A-Sepharose affinity and chromatofocusing columns. The purified enzyme was able to hydrolyse all phosphatidylinositol substrates with optimum at pH 7.0 and activation by Ca2+, Cd2+ and Mn2+ but not phospholipids lacking the inositol residue. 4. In PAGE (8-25% gradient) the purified (aggregated) enzyme did not enter the gel. In SDS-PAGE two closely located bands were found with Mr-values of 15,000 and 18,000. Isoelectric focusing showed a wide band at pl 4.5-5.1. 5. Gel filtration resulted in a broad elution peak indicating multiple molecular forms (aggregates); the basic form had an apparent molecular weight of 100,000. The binding of the enzyme to Con A-Sepharose indicated that the enzyme is a glycoprotein.

Dipeptidyl peptidase III and alanyl aminopeptidase in the human seminal plasma: origin and biochemical properties.

Human seminal plasma contained two distinct enzyme activities hydrolysing ArgArgNA. The enzymes were separated by anion exchange chromatography and further purified by gel filtration and/or hydrophobic interaction chromatography. The enzyme eluting at the lower NaCl concentration (0.26 mol/l) displayed an optimum at pH 5.7-6.0 (enzyme A), while the other enzyme eluted at 0.32 mol/l NaCl and showed an optimum at pH 8.5-9.0 (enzyme B). Enzyme A was found to coelute with an aminopeptidase which hydrolysed various amino acid derivatives as well as dipeptide naphthylamides sequentially. Both enzymes were sensitive to heavy metal ions (Cd, Cu, Hg, Pb) and chelating agents (EDTA, o-phenanthroline) and moderately sensitive to di-isopropylfluorophosphonate (DFP) or phenylmethylsulfonylfluoride (PMSF). After EDTA suppression both activities were partially reactivated by divalent metal ions, particularly by Co2+. Enzyme A was highly sensitive to amastatin, bestatin and puromycin, while enzyme B was not markedly influenced. With different substrates the modifier characteristics of enzyme A were equal. High concentrations of some substrates suppressed the hydrolysis rates of both enzymes. Enzyme B was much more sensitive to the thermal treatment than enzyme A. Tentative molecular masses of 110 kD and 80 kD were obtained for enzymes A and B, respectively. Enzyme B was found in all male reproductive tissues (testis, epididymis, vas deferens, ampulla, seminal vesicles, prostate), while enzyme A was only detected in the prostatic homogenate. Thus, ArgArgNA in the human seminal plasma is hydrolysed by dipeptidyl peptidase III, which may originate from different reproductive organs, while the prostate is responsible for the secretion of an aminopeptidase with a wide substrate spectrum including dipeptidyl derivatives.

Electron microscopic study of the secretion process in bovine reproductive organs.

The origin and mechanism of the secretion of membrane-bound particles in bovine seminal plasma were studied with transmission (TEM) and scanning (SEM) electron microscopy of the epididymis, vas deferens, ampulla, and seminal vesicle of adult bulls. In the SEM study, all these organs were found to contain apical protrusions in the lining of the epithelial cells. Eventually the protrusions became detached and formed secretory bodies within the lumina of these organs. In the epididymis, the TEM study disclosed a granular and rather homogeneous content in the protrusions and bodies, whereas in the vas deferens they contained dilated cisternae of smooth endoplasmic reticulum. In the ampulla and seminal vesicle, the formation of the apical protrusions was associated with an accumulation of membrane-bound vesicles. These vesicles were found to be released from the storage bodies into the secretory fluid of the lumen. Both could be harvested from isolated seminal vesicle secretions by Percoll gradient centrifugation. It was concluded that various parts of the bovine reproductive organs discharge their secretory products at least partly by an apocrine mechanism. The membrane-bound particles in the seminal plasma, however, appear to be mainly derived from the ampulla and seminal vesicle.

Selenium and glutathione peroxidase in seminal plasma of men and bulls.

High levels of selenium and glutathione peroxidase (GSH-Px) were found in bull seminal plasma but low concentrations in human seminal plasma. In man the seminal plasma selenium was associated with two macromolecules separable by gel filtration, but no GSH-Px was found in the same fractions. Selenium in bull seminal plasma was associated with two proteins, which could be separated by gel filtration and anion exchange chromatography. Both macromolecules coeluted with GSH-Px activity and had identical optima at pH 7.0. Their responses to thermal treatment, however, differed. Seminal vesicle secretory fluid in the bull contained both these proteins, while the larger molecule was also found in fractionations of ampulla, prostate and Cowper's glands. The larger enzyme form is evidently a tetramer of the smaller one. Both enzyme forms were extremely sensitive to heavy metals and some divalent metal ions. GSH caused an activation while other reducing agents were suppressive. Triton X-100 had no effect, while sodium deoxycholate was inhibitory. These properties are typical for a phospholipid hydroperoxide GSH-Px. It is concluded that this selenium-dependent enzyme may be important in the protection of bovine spermatozoa against damage caused by oxygen radicals, while in man such a mechanism is not functional.

Gamma-glutamyl transpeptidase, glutathione, and L-glutamic acid in the rat epididymis during postnatal development.

During postnatal development, gamma-glutamyl transpeptidase (gamma-GT), reduced glutathione (GSH), and L-glutamic acid (L-Glu) were assayed in the epididymides of rats at 5-day intervals between 10 and 60 days of age and compared to adult levels. gamma-GT activity (with gamma-glutamyl-p-nitroanilide as substrate) and L-Glu (nicotinamide adenine dinucleotide conversion-dependent assay) were measured photometrically, while GSH (o-phthalaldehyde reaction) was quantified with a fluorometric assay. In immature rats, the epididymal gamma-GT was very low but increased after 25 days of age in the caput and after 50 days of age in the cauda. The enzyme level in the epididymal caput was by far the highest in the adult rat reproductive tissues. The postnatal increase of gamma-GT in epididymal caput and cauda was associated with a decline of its substrate GSH and an accumulation of the product L-Glu. These observations provide evidence for the in vivo hydrolytic activity of gamma-GT and explain the high levels of L-Glu found in the epididymis of rats and other mammals.

Sphingomyelinases in human, bovine and porcine seminal plasma.

The seminal plasma of man, boar and bull was found to have a sphingomyelinase (SMase) activity hydrolysing [N-methyl-14C]sphingomyelin. The human and porcine enzymes had an acid pH optimum and were not influenced by divalent metal ions or chelating agents. They were closely similar with the lysosomal enzyme in many tissues. The bovine seminal plasma SMase was partially purified. The enzyme was a glycoprotein with pH optimum at 6.5, a broad pI 4.2-4.8 and molecular mass of 160 and 60 kDa, respectively, in native and SDS-PAGE. The enzyme was activated by Co greater than Mn greater than Cd greater than Ni and inhibited by chelating agents, Cu, Fe, Pb and Zn. The enzyme was clearly distinct from the acid lysosomal SMase and the previously described neutral Mg2+-dependent and independent activities. It had a wide distribution in the bull reproductive tissues.

Glutathione, L-glutamic acid and gamma-glutamyl transpeptidase in the bull reproductive tissues.

The distribution of glutathione (GSH), L-glutamic acid (Glu) and gamma-glutamyl transpeptidase (gamma-GT) was studied in bull reproductive organs and fluids. Glutathione, the physiological substrate of gamma-GT, was localized specifically by a fluorescence method in the testis, epididymis and spermatozoa. Of the reproductive tissues, the testis, caput epididymis and ampulla had the highest levels of GSH, but it was also present in seminal fluid. Washed caput epididymal sperm had three times the GSH content of cauda epididymal or ejaculated sperm. In spermatozoa, GSH displayed maximal staining in the midpiece and tail regions. The highest levels of gamma-GT were encountered in the epididymis. The concentration of Glu was also high in the epididymis. Its formation may be due to the hydrolytic activity of gamma-GT, which, in addition, may have an important role in the transfer of Glu residues to reactive groups on the sperm surface.

Lectin binding of subunits of placental and serum oxytocinase after electrophoresis and transblotting to nitrocellulose.

1. Oxytocinase enzymes were purified from maternal serum and human placenta, run by SDS-PAGE and transferred onto nitrocellulose. Both enzymes were homogeneous in protein staining with Mr of 145,000. 2. Both serum and placental oxytocinases bound concanavalin A (Con A), limax flavus agglutinin (LFA) and wheat germ agglutinin (WGA). The WGA-binding of the placental enzyme was more strongly inhibited by 0.2 M N-acetylglucosamine than that of the serum enzyme which may indicate a higher sialic acid content in the serum enzyme. 3. Neuraminidase treatment did not affect the binding of Con A but decreased the binding of WGA to serum and placental enzymes. Serum enzyme showed a pl 4.7 on isoelectric focusing.

Determination of selenium in human spermatozoa and prostasomes using base digestion and electrothermal atomic absorption spectrophotometry.

A method for the determination of selenium in human spermatozoa and prostasomes is described. The samples were digested with 25% (w/v) tetramethylammonium hydroxide (TMAH) in methanol and analyzed by atomic absorption spectrometry with electrothermal atomization and Zeeman background correction (ET-AAS). Nickel was used as a matrix modifier. Calibration was performed using the matrix-based calibration curve. The TMAH-digestion method agreed well with a conventional digestion procedure using concentrated nitric acid. The TMAH-digestion does not require heating or strong acids and it was suitable for small biological samples. The average recovery of added selenium in spermatozoan digests was 95.1 +/- 5.2% (n = 5). The coefficient of variation was 9.1% (n = 21). The accuracy of the method tested with the NBS standard 1577 (bovine liver, certified at 1.1 +/- 0.1 micrograms Se/g) resulted in a value of 0.98 +/- 0.10 micrograms Se/g (n = 16). The method was further tested in an interlaboratory comparison study.

Lead, magnesium, selenium and zinc in human seminal fluid: comparison with semen parameters and fertility.

The concentrations of lead, magnesium, selenium and zinc in seminal fluid from men with variable semen quality (sperm morphology, density and motility) and fertility were determined by atomic absorption spectrometer without or with Zeeman background correction. The mean (+/- SD) concentration of selenium in the samples (n = 142) was 28.8 +/- 9.5 micrograms/l, which was about a third of the corresponding serum value (77.8 +/- 13.3 micrograms/l, n = 140). The serum selenium level was significantly (P less than 0.001) higher in infertile than in fertile men, but the seminal fluid did not show such a difference. No correlation was obtained between selenium values in seminal plasma and sperm density or motility. The levels of lead in seminal fluid were very low with no correlation to the levels of magnesium, selenium and zinc or the semen qualities. The seminal fluid lead concentration was significantly (P less than 0.001) higher in infertile (3.6 +/- 3.2 micrograms/l, n = 79) than in fertile men (1.7 +/- 1.0 micrograms/l, n = 39). Magnesium (103.5 +/- 49.2 mg/l, n = 90) and zinc (141.1 +/- 71.7 mg/l, n = 157) concentrations in seminal fluid were comparable with previous reports. Both minerals showed a positive correlation to the seminal fluid selenium, while only zinc displayed a borderline correlation with sperm density. The present findings indicate that the determination of seminal fluid selenium may not offer any advantages over zinc and magnesium measurement in the fertility assessment and its role in human semen remains obscure. The low lead concentrations in the present material is a clear indication of low industrial exposure.

An enzymatic colorimetric assay of calcium-dependent phospholipases A.

In this paper we describe a new method for the assay of calcium-dependent phospholipases A. In this method released fatty acids are quantitated by an enzymatic colorimetric reagent kit which is commercially available. We have tested the applicability of this assay with enzymes from porcine pancreas (phospholipase A2), snake venom (phospholipase A2), and Rhizopus arrhizus (a lipase with phospholipase A1-like activity) as well as with a phospholipase A2 activity of bovine seminal vesicle fluid. We conclude that the kit procedure is a convenient, rapid and sensitive endpoint assay for calcium-dependent phospholipases A.

Biochemical studies on dipeptidyl peptidases I to IV of the human placenta.

Homogenates of human term placentae were utilized to demonstrate the presence of four dipeptidyl peptidases (DPP I to IV) after sequential fractionations with gel filtration and anion-exchange chromatography. DPP I was assayed with SerTyrNA as substrate and showed the characteristics of a thiol-dependent serine enzyme with optimum at pH 4.5 and a molecular weight of 210,000. DPP II, analysed with LysAlaNA as substrate, had an optimum at pH 5.5 and a molecular weight of 130,000 with no dependence on thiol groups or divalent ions. DPP III was studied with ArgArgNA as substrate. It was optimally hydrolysed at pH 8.8 and had a molecular weight of 84,000. The enzyme was highly suppressed by chelating agents but could be reactivated by Co2+ and some other divalent ions. DPP IV, with GlyProNA as substrate, displayed an optimum at pH 8.2. The fractionations displayed multiple forms of the enzyme, possibly indicating the presence of proto- and polymeric DPP IV activities. The protomer had a molecular weight of 260,000 and showed no dependence on thiol groups but was sensitive to Zn2+.