Types A and B monoamine oxidase contribute to the metabolism of norepinephrine in perfused lungs of rats

The aim of the study was to determine the activity of monoamine oxidase (MAO) and the contributions of the A and B forms of MAO to the metabolism of norepinephrine (NE) in isolated perfused lungs of the rat. Preliminary experiments to investigate the MAO-A and MAO-B selective inhibitors, Ro41-1049 and Ro19-6327, respectively, were carried out in isolated preparations of rat vas deferens incubated in 10 nM [3H]NE (Uptake2 and catechol-O-methyltransferase inhibited) to measure rates of deamination of NE and the rate constant for deamination (kMAO) by MAO-A. These experiments showed that 1) the IC50 of Ro41-1049 for inhibition of MAO-A was 9.62 nM with 97% inhibition by 300 nM and 2) 100 or 300 nM Ro19-6327 did not affect deamination of NE by MAO-A. Hence, 300 nM Ro41-1049 and 100 nM Ro19-6327 were used to inhibit selectively MAO-A and MAO-B, respectively, in rat lungs perfused in vitro with 10 nM [3H]NE. Catechol-O-methyltransferase was inhibited and kMAO values for metabolism of NE were determined. The kMAO value for deamination of NE in the absence of Ro41-1049 or Ro19-6327 was 0.186 min-1. Ro41-1049 and Ro19-6327 decreased this kMAO value by 79 and 33%, respectively. Thus, it was concluded that both MAO-A and MAO-B contribute to the deamination of NE in the pulmonary circulation of the rat, with MAO-A responsible for 67-79% of the total deamination and MAO-B for 21-33%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptive supersensitivity in the guinea pig vas deferens is associated with a reduction in the abundance of the alpha 2 subunit isoform of Na+/K(+)-ATPase

Adaptive supersensitivity has been demonstrated previously in the guinea pig vas deferens after chronic treatment with reserpine, postganglionic denervation, or preganglionic denervation. The magnitude of the change in sensitivity was similar regardless of the method of induction; the underlying mechanism was identified as a partial depolarization secondary to reduced activity of the Na+/K+ pump. Experiments were conducted to quantitatively determine whether the identified losses in Na+/K(+)-ATPase activity and [3H]ouabain binding were due to reductions in the levels of specific protein subunits of the sodium pump. Electrophoretic separation and quantification of the abundance of alpha subunit isoforms were accomplished using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and slot blot analysis. Supersensitivity was induced in the guinea pig vas deferens through pretreatment with reserpine (1.0 mg/kg/day x 5 days). The abundance of the alpha 2 subunit isoform was reduced by 41% in tissue homogenates obtained from animals treated with reserpine, compared with untreated controls. In contrast, there was no significant alteration in the alpha 1 subunit isoform (a protein similar in size to that previously identified in vascular smooth muscle as a "truncated" form of the protein). These data suggest that the adaptation of the guinea pig vas deferens after a chronic reduction in net stimulus is mediated through a change in a specific cellular protein. This evidence supports the assignment of the alpha 2 subunit isoform as the specific protein responsible for the development of nonspecific adaptive supersensitivity in the guinea pig vas deferens.

Androgenic regulation of glycolytic and HMP pathway in epididymis and vas deferens of rhesus monkey

The androgenic regulation of the eleven enzymes of glycolytic pathway and two key enzymes of HMP pathway was studied in the initial segment, caput, corpus and cauda regions of the epididymis and in the vas deferens of rhesus monkey. The specific activities of enzymes were expressed as units of activity per mg DNA. Results in control animals indicate a marked difference in energy metabolism of epididymis and vas deferens. However, the epididymal duct itself did not show much regional variation in enzyme activities along its length. All the enzymes of the two pathways studied showed significant reduction after castration, the regulatory enzymes being affected more severely. On treatment with exogenous dihydrotestosterone, most of these enzymes showed stimulation in castrated monkeys, but none of them could be restored to normal level. The stimulation of these enzymes on treatment with exogenous dihydrotestosterone varied along the epididymal duct itself being maximum in the initial segment and minimum in the cauda region. The changes in the vas deferens were less marked as compared to the epididymis following castration and androgen replacement.

Proteolytic enzymes in seminal plasma of domestic turkey (Meleagris gallopavo)

Protease and basic amidase activity was found in the seminal plasma of the domestic turkey. Amidase activity, measured through use of N-alpha-benzoyl-DL-arginine-p-nitroanilide-HCL (BAPNA), was 23-28 times greater for turkey than for guinea fowl or chicken. Within the reproductive tract, seminal plasma from the vas deferens had much greater activity than testicular or epididymal fluids. Turkey seminal plasma enzyme (TSPE) purified by chromatography or isoelectric focusing showed three protein bands by PAGE, each resolving on SDS-PAGE into two subunits with molecular weights of approximately 28,000-32,000 and 38,000-44,000. One of the three proteins also contained a larger subunit (M(r) 76,000-81,000) thought to be transferrin. Turkey acrosin consisted of three subunits with molecular weights below 20,500. Acrosin, but not TSPE, was visualized in native gels with N-alpha-benzoyl-DL-arginine-beta-naphthylamide (BANA)/Fast Garnet stain. Michaelis constants (BAPNA) for TSPE, acrosin, and trypsin were 2.41 +/- 0.12 x 10(-4) M (n = 5), 4.96-6.03 x 10(-4) M (n = 2), and 6.76 +/- 0.95 x 10(-4) M (n = 6), respectively. TSPE, like acrosin and trypsin, was inhibited by benzamidine but not iodoacetamide. While all natural trypsin inhibitors tested inhibited acrosin, TSPE was not inhibited by ovomucoid from chicken or turkey egg white.

Immunocytochemical localization of the Yf subunit of glutathione S-transferase P shows regional variation in the staining of epithelial cells of the testis, efferent ducts, and epididymis of the male rat

Glutathione S-transferases (GSTs) are a family of isozymes that catalyze the conjugation of glutathione (GSH), a tripeptide found in all mammalian cells; this function plays a protective role, as the addition of GSH to an electrophile generally forms a less toxic product. The pi class of GSTs contains homodimers of the Yf subunit, also known as Yp or rat subunit 7; this subunit is found in high concentrations in the testis and epididymis. The objective of the present study was to localize immunocytochemically the Yf subunit in the testis and in the various regions of the epididymis using light, electron, and confocal microscopy. In the testis, immunoperoxidase staining was localized exclusively to Sertoli and Leydig cells. The low cuboidal epithelial cells of the rete testis and the sparse ciliated cells of the ductuli efferents were also immunoreactive. A distinct pattern of immunostaining for the Yf subunit was observed in the different regions of the epididymis. The proximal area of the initial segment showed intense reactivity localized to epithelial basal cells. Basal cells in the middle area of the initial segment were also reactive, as were a second unidentified population of cells located in the apical region of the epithelium. The epithelium, including both principal and basal cells, in the distal initial segment, intermediate zone, and proximal caput epididymidis showed a weak, moderate, or strong degree of reactivity, respectively. In the distal caput epididymidis, however, principal cells showed a checkerboard-like pattern of immunoreactivity, with some cells being intensely stained or faintly stained, whereas others were unreactive. Strikingly, in the corpus and proximal cauda epididymidis, intense immunostaining was localized exclusively over the epithelial basal cells. As viewed in the light and confocal microscope, the intensely stained basal cells showed extensive processes that covered most of the base of the epididymal tubule. Upon quantitation of the immunogold labeling density (the number of gold particles/microns2) in principal and basal cells of the different regions of the epididymis, we observed a sharp decline in immunogold labeling of principal cells coupled with a dramatic increase in labeling of basal cells as we progressed along the tissue, particularly in the transition from the caput to the corpus epididymidis. This study constitutes the first demonstration of a protein that is selectively expressed in epithelial basal cells of the corpus and proximal cauda epididymidis.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of CuZn-superoxide dismutase in the human male genital organs

We performed an immunohistochemical analysis using a polyclonal antibody to determine the localization of CuZn-superoxide dismutase (SOD), a scavenger of superoxide anion radicals, in the human male genital organs. In the testis, intense immunoreactivity of CuZn-SOD was shown in both the cytoplasm and nucleus of the spermatogonia of the seminiferous tubules. Spermatocytes, further differentiated germ cells and Sertoli cells showed no or weak immunoreactivity. In the ductus epididymis, the principal cells showed no or weak immunoreactivity except for the stereocilial region, while the basal cells showed relatively intense immunoreactivity. In the ductus deferens, the prostate and the seminal vesicles, columnar and cuboidal epithelia showed CuZn-SOD immunoreactivity. The immunoreactivity was more intense in the epithelia of the ductus deferens than in the prostate or the seminal vesicles. Basal cells in the prostate also showed intense immunoreactivity. Collectively, the present immunohistochemical results suggest that CuZn-SOD in the male genital organs is localized where it could play an important role in cell differentiation, including spermatogenesis. The CuZn-SOD could also play a role in local defence mechanisms against tissue damage mediated through superoxide anion radicals, as well as in providing SOD to the seminal plasma.

Presence of a phosphoramidon-sensitive endothelin-converting enzyme which converts big-endothelin-1, but not big-endothelin-3, in the rat vas deferens

Endothelin-1 (ET-1) enhanced field stimulation-evoked (0.1 Hz), nerve-mediated contractions of the prostatic portion of the rat vas deferens. The human precursor of ET-1, big-endothelin (1-38) (big-ET-1) was only two-fold less potent than ET-1 (pD2 values: 7.30 and 7.49, respectively). The threshold concentrations necessary to elicit an increase of the response to electrical stimulation was lower for ET-1 (5 nmol/l) than for big-ET-1 (25 nmol/l). Endothelin-3 (ET-3) also markedly enhanced the response of the tissue to field stimulation with a potency similar to ET-1 (pD2 value: 7.59). In contrast, the precursor of ET-3, big-endothelin (1-41) (big-ET-3), was inactive at concentrations up to 0.5 mumol/l. Treatment of the preparations with phosphoramidon (50 mumol/l) markedly reduced the twitch enhancement by big-ET-1 without affecting the response to ET-1. Our results suggest the presence of a specific phosphoramidon-sensitive endothelin-converting enzyme which converts big-ET-1 to ET-1 in the rat vas deferens.

Characterization of nitric oxide synthases in non-adrenergic non-cholinergic nerve containing tissue from the rat anococcygeus muscle

Tissue homogenates prepared from rat anococcygeus muscle converted L-arginine to L-citrulline indicating the presence of nitric oxide (NO) synthase. NO synthase activity was also found in crude and partially-purified soluble and particulate fractions prepared from the homogenates. Both soluble and particulate NO synthase were dependent on NADPH, 5,6,7,8-tetrahydrobiopterin and calcium, and inhibited by NG-nitro-L-arginine. Tissue homogenates or crude cytosolic and membrane fractions from rat vas deferens, which does not contain NO releasing non-adrenergic non-cholinergic neurones, had no NO synthase activity.

Selective action of androgens on the molecular forms of esterases characterized by two-dimensional gel electrophoresis in the epididymis and vas deferens of the mouse

Molecular forms of esterases were resolved in non-denaturing conditions by using two-dimensional gel electrophoresis with isoelectric focusing in the first dimension and a time-dependent polyacrylamide gradient gel electrophoresis (PAGGE) in the second dimension. This procedure was used to analyse sequential changes in esterase composition along the excurrent genital duct of the mouse and to initiate a specific identification of the androgen-regulated molecular forms. Almost all the 68 variants (pH 3.9-6.4 and 50-300 kDa) revealed by alpha-naphtyl acetate from the fluids of the three parts of the epididymis (caput, corpus, cauda) and vas deferens, could be assigned to the carboxylesterase group as shown by their action on various substrates and sensitivity to inhibitors. Some of these variants co-migrated with those in the serum and testis, whereas other enzyme forms made their first appearance in the caput (13), in the corpus (26) and in the vas deferens (3). The major changes occurred between the caput and the corpus of the epididymis. Only a few acidic spots were not revealed after neuraminidase digestion. Castration of mice (4 weeks) resulted in inhibition of the activity of 34 esterase forms, and thus abolished most of the regional differences in the excurrent duct system. By re-initiating or repressing the synthesis of regional esterase variants, testosterone supplementation (2 and/or 4 weeks) of castrated animals restored the normal esterase pattern in the three epididymal parts, but not in the vas deferens. The major effect of efferent duct ligation (4 weeks) was the emergence in the corpus and cauda of the epididymis of two variants found in the caput of uncastrated mice.

The oxidation of dopamine by the semicarbazide-sensitive amine oxidase (SSAO) from rat vas deferens

The activities of monoamine oxidase A and B and the semicarbazide-sensitive amine oxidase from rat vas deferens were compared towards benzylamine and dopamine. The selective inhibitors (-)-deprenyl and clorgyline were used to allow the contributions of the A and B forms of monoamine oxidase to be determined separately. Comparison of the kinetic constants of the three enzymes towards dopamine indicated that, although each of them had activity towards this substrate, their relative contributions to the total oxidative deamination would depend on the substrate concentration. At all concentrations in the range 1 microM to 10 mM monoamine oxidase-B would contribute about 50% of the total activity. In the range 1 to 10 microM the contributions made by activities of monoamine oxidase-A and the semicarbazide-sensitive enzyme were similar but at higher concentrations the activity of the latter enzyme became more important, its contribution to the total activity rising to some 35% of the total at 500 microM dopamine. The activity of the semicarbazide-sensitive enzyme towards dopamine might thus be important under conditions where either or both the monoamine oxidases were inhibited in pharmacological studies. Its possible relevance to Norrie disease, in which both forms of the human enzyme are deficient, requires further examination.

Lack of correlation between activation of cyclic AMP-dependent protein kinase and inhibition of contraction of rat vas deferens by cyclic AMP analogs

The effects of N6,O2-dibutyrl-adenosine-3',5'-cyclic monophosphate (db-cAMP) and 8-bromo-adenosine-3',5'-cyclic monophosphate (8-Br-cAMP) on tension and cAMP-dependent protein kinase (PKA) activities in rat vas deferens were investigated. A soluble enzyme fraction obtained from the vas deferens was found to contain both type I and type II isozymes of PKA, whereas a particulate fraction contained only the type II isozyme. Exposure of the vas deferens to db-cAMP (1-100 microM) for 30 min caused a concentration-dependent inhibition of phenylephrine-induced contractions, with an EC50 of less than 10 microM. 8-Br-cAMP had no significant effect on contractions over a similar concentration range. Both of the analogs were able to activate PKA significantly at a concentration of 10 microM, and the magnitude of the PKA activation was greater with 8-Br-cAMP than with db-cAMP. Charcoal was added to the homogenization buffer in these experiments to prevent the artifactual activation of PKA by cAMP analogs trapped in the extracellular space. The ability of db-cAMP, but not 8-Br-cAMP, to inhibit the contraction of vas deferens could not be explained on the basis of differential activation of soluble or particulate PKA or of specific isozymes of the enzyme. It is, therefore, concluded that activation of PKA is not responsible for the relaxant effects of cAMP analogs in some smooth muscle.

The localization of the beta-subtype of protein kinase C (PKC-beta) in rat sympathetic neurons

The localization of PKC-beta was studied in rat sympathetic neurons using a polyclonal antibody specific for the beta 1- and beta 2-subspecies. The tissues studied included the superior cervical (SCG) and hypogastric (HGG) ganglia and the target tissues of the SCG and HGG neurons: the submandibular gland, iris, prostate and vas deferens. PKC-beta-LI was found in nerve fibers in both ganglia. A proportion of the fibers in the SCG disappeared after decentralization, suggesting that the fibers were of both pre- and postganglionic origin. The somata of the HGG and SCG neurons expressed varying amounts of PKC-beta-LI, the majority of SCG neurons being labelled only after colchicine treatment. In all target tissues there were PKC-beta-immunoreactive nerve fibers in bundles, but the most peripheral branches of the fibers were negatively labelled. The results show that PKC-beta-LI is widely present in sympathetic postganglionic neurons with mainly quantitative differences. The lack of PKC-beta in the most peripheral branches of nerve fibers might be a general feature of sympathetic postganglionic neurons, suggesting that the participation of PKC-beta in neurotransmitter release and in other functions in nerve terminals in sympathetic adrenergic neurons is unlikely.

Carbonyl reductases from rat testis and vas deferens. Purification, properties and localization

Three enzyme forms (T1, T2, T3) from rat testis and two from rat vas deferens (V1, V2) of carbonyl reductase have been highly purified to apparent homogeneity. These carbonyl reductases from rat reproductive organs have several similarities in terms of molecular mass (32-33 kDa), isoelectric point (pI 5.9-6.4), immunochemical properties, cofactor requirement (NADPH dependency) and sensitivity to sulfhydryl reagents. The isoenzymes from the vas deferens (V1, V2) have similar catalytic activities, whereas those from the testis (T1, T2, T3) showed different catalytic activities from each other. All enzymes, however, reduced quinones, aromatic aldehydes and ketones, while T3, V1 and V2 were characterized as possessing high affinity towards prostaglandins. An immunoinhibition study using a specific antibody indicated that these enzymes were solely responsible for the overall catalytic activities of 13, 14-dihydro-15-oxo-prostaglandin F2 alpha, 4-benzoylpyridine, and 4-nitroacetophenone reduction and prostaglandin F2 alpha oxidation in both testis and vas deferens cytosol. The immunohistochemical staining revealed a positive immunoreactivity to antibody only in the Leydig cells of the testis, but neither the germ cells nor Sertoli cells in the seminiferous tubule. The staining also showed that the enzymes in the vas deferens were primarily localized in mucosal epithelium cells.

Role of adenylate cyclase in modulatory effect of neuropeptide Y on [3H]noradrenaline release in guinea-pig vas deferens

1. The effect of neuropeptide Y (NPY) on [3H]noradrenaline ([3H]NA) release-evoked by 5-Hz electrical stimulation or 5 microns calcium ionophore A23187 was studied in vitro in guinea-pig vas deferens. 2. The evoked tritium overflow (which reflected [3H]NA release) was determined by liquid scintillation spectrometry. 3. NPY, 1 microM, reduced electrically-evoked tritium overflow. NPY reduction was more pronounced upon 20-sec, 3 msec continuous stimulation (73.2 +/- 4.4%) and upon 5-min, 1 msec intermittent stimulation (47.8 +/- 2.4%) as compared to the reduction upon 5-min, 1 msec continuous stimulation (24.3 +/- 3.8%). Forskolin (0.1-1 microM) and theophylline (0.65-1.25 mM) dose-dependently diminished this NPY reducing effect. 4. NPY, 1 microM, reduced A23187-evoked tritium overflow by 52.3 +/- 7.1%. Forskolin (5 microM) and theophylline (1.25 mM) significantly decreased the effect of NPY. 5. It is concluded that in guinea-pig vas deferens NPY reduces [3H]NA release through affecting adenylate cyclase and the processes responsible for calcium mobilization.

Immunohistochemical localization of prostaglandin H synthase in the epididymis and vas deferens of the mouse

Prostaglandins (PGE2, PGF2 alpha) in the excurrent ducts of the male reproductive tract appear to be both modulators of ductal contractility for transport of spermatozoa and factors involved in the regulation of sperm maturation. To identify the tissue sites for the production of prostaglandins (PGs) in the excurrent ductal system, we have employed an immunohistochemical technique to localize prostaglandin H (PGH) synthase in the epididymis and vas deferens of the mouse. A mouse monoclonal antibody to PGH synthase was used and was shown to be specific for the mouse enzyme by Western blot analysis. In sexually mature mice, PGH synthase was primarily localized to the epithelium of the epididymis and vas deferens. Within the epididymal epithelium, immunoactivity appeared in all cell types of the initial segment, in a subpopulation of cells with predominantly apically oriented nuclei in the caput and corpus, and in low levels in the cauda. PGH synthase reactivity was the most intense in the epithelial cells of the vas deferens. PGH synthase was not detected in smooth muscle cells, spermatozoa, or luminal fluid. This study suggests that the epithelium of the excurrent ductal system of the mouse is the major site for PG production. The regionalization of PGH synthase to cells in the epididymis thought to be involved in the absorption of luminal fluid suggests that PGs may play a role in fluid and ion transport.

Heterogeneity of the effects of monensin on two types of contractions evoked by inhibition of Na+-K+ ATPase in the guinea-pig vas deferens

The interactions between ouabain or K+-free medium and monensin on noradrenaline (NA) release and Ca2+-evoked contractions were assessed in guinea-pig vas deferens. Ouabain (10 microM) produced large, sustained contractions and monensin (1 microM) small, transient contractions. The ouabain-evoked contraction tended to be potentiated in the presence of monensin. The marked contraction induced by ouabain plus monensin was nearly abolished by phentolamine or by treatment with 6-hydroxydopamine. Ouabain caused the release of NA from the tissue, as determined in an HPCL-ECD study. This ouabain-evoked release of NA was enhanced by the simultaneous administration of monensin. High Ca2+ (10 mM) per se, ouabain, monensin or K+-free medium did not elicit contraction of the tissue in the presence of phentolamine. However, 10 mM Ca2+ caused a large contraction 45-65 min after exposure to ouabain or K+-free medium and this contraction was suppressed by monensin. The contraction evoked by Ca2+ in the presence of ouabain was further inhibited by amiloride, an inhibitor of Na+-Ca2+ or Na+-H+ exchange transport, but not by nifedipine, a voltage-dependent Ca2+ antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of norepinephrine levels, tyrosine hydroxylase and dopamine-beta-hydroxylase activities after castration and testosterone treatment in vas deferens of adult rats

Norepinephrine levels and tyrosine hydroxylase and dopamine-beta-hydroxylase activities have been used to evaluate the effect of castration and testosterone treatment on the sympathetic innervation of the adult vas deferens. Castration was followed by a decrease in both norepinephrine content and tyrosine hydroxylase activity, even though the changes were not concomitant. Treatment of castrated animals with testosterone reversed the effect of castration on organ weight and norepinephrine content, but only a short-lasting increase in tyrosine hydroxylase activity occurred at the beginning of testosterone treatment. In contrast, the testosterone-induced recovery of norepinephrine content observed at this time was accompanied by a marked increase in dopamine-beta-hydroxylase activity. The results suggest that in rat vas deferens, norepinephrine levels are under androgenic control and that this regulation mainly involves changes in dopamine-beta-hydroxylase activity rather than a modulation of tyrosine hydroxylase.

Effects of haloperidol on neurotransmitter activity in the rat vas deferens

1. The effects of haloperidol on the responses of the isolated rat vasa deferentia to catecholamines and ACh were studied. 2. Haloperidol produced a competitive antagonism to responses elicited by NA and DA in the vas deferens. 3. The M1 and M2 muscarinic responses to ACh of the vas deferens were potentiated by this neuroleptic. 4. The AChE activity of the vas deferens was significantly depressed by pretreatment with haloperidol. 5. The ability of haloperidol to lower AChE activity was compared with that of neostigmine and it may be due to a similar molecular mechanism. 6. The present results suggest that haloperidol has anti-AChE properties that may be responsible for the potentiation of the responses to ACh. 7. The study indicates that haloperidol has a wider range of pharmacological actions than previously reported.

[N-acetyl-beta-D-glucosaminidase (NAG) activity in human semen: its relation to gamma-glutamyl transpeptidase (gamma-GTP) activity in seminal plasma and reproductive tissues, and relation between seminal mucoprotein concentration and seminal NAG, and gamma-GTP activities]

N-Acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyl transpeptidase (gamma-GTP) activities in seminal plasma obtained from male infertile patients and these activities in reproductive tissues obtained from cryptorchids and patients with bladder tumors were studied. Seminal mucoprotein concentration was also measured. The mean NAG and gamma-GTP activity in seminal plasma was 2,092 +/- 794 mU/ml and 10,942 +/- 4,179 mIU/ml, respectively. The mean seminal mucoprotein concentration was 28.0 +/- 5.7 mg/ml. In seminal plasma, a significant correlation was obtained between NAG and gamma-GTP (p less than 0.001). and between gamma-GTP and mucoprotein concentration (p less than 0.05). However, there was no correlation between NAG and mucoprotein concentration. In the reproductive tissue high gamma-GTP activity was observed in the testicular tissue and in the external gland of the prostate. The activity in the epididymis was higher in the tail than in the head. High NAG activity was observed in the epididymal head and in the internal gland of the prostate. In the testicular tissue, NAG activity was low. These findings showed that in the seminal plasma NAG and gamma-GTP activities were closely related but in the reproductive tissue, these activities located in different areas.

Inhibition of tyrosine hydroxylase in rabbit mesenteric artery and vas deferens by catechol oestrogens

In the present study we have investigated the effects of oestrogens, catechol oestrogens, and catecholamines on tyrosine hydroxylase (TH) activity derived from rabbit mesenteric artery and vas deferens. Both catechol oestrogens, 2-hydroxyoestradiol (2OHE2) and 2-hydroxyoesterone (2OHE1), inhibited TH activity in mesenteric artery and vas deferens in a concentration-dependent manner with potencies that were higher than those for noradrenaline but lower than that for dopamine. When added to the reaction medium along with increasing concentrations of a pterin cofactor (200 to 1,500 mumol/l DMPH4), the catechol oestrogens (200 mumol/l) increased the apparent Km for DMPH4 without altering the maximum velocity (Vmax) of the reaction. Similar results were obtained with the addition of noradrenaline (200 mumol/l) and dopamine (120 mu/mol). Apparent Ki values obtained for the catecholamines and catechol oestrogens were within the same order of magnitude and varied from 30 mumol/l for dopamine and 2OHE2 to 183 mumol/l for 2OHE1. Oestradiol (E2) and 2-methoxyoestradiol (2MeOE2), i.e., oestrogens that do not possess a catechol moiety, exhibited only weak inhibitory effects on TH activity. At the highest concentration tested (1 mmol/l), they did not reduce enzyme activity below 58% of control values. Kinetic analysis revealed that these two oestrogens did not consistently affect either the Vmax of hydroxylation or the Km for DMPH4. It is concluded that catechol oestrogens inhibit TH activity with a potency comparable to noradrenaline and dopamine. This inhibition is by competition with the pterin cofactor. Oestrogens that to not possess a catechol moiety are not effective inhibitors of TH.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin E2 20-hydroxylase in ampulla of vas deferens of sheep

Microsomes were prepared from the ampullary mucosa of ram ductus deferens. The microsomal fraction was supplemented with 1 mM NADPH and was found to metabolize PGE2 to 20-hydroxy-PGE2. The product was identified by gas chromatography-mass spectrometry (GC-MS). The biosynthesis of 20-hydroxy-PGE2 was assessed by reversed-phase high performance liquid chromatography (HPLC) using 19-hydroxy-PGE1 as an internal standard and 0.2 mM PGE2 was found to be metabolized to 20-hydroxy-PGE2 at a rate of 7.1 pmol min-1 mg-1 of protein. Like a prostaglandin 20-hydroxylase of sheep vesicular glands, the 20-hydroxylase of the ampulla was only partly inhibited by metyrapone. 20-Hydroxy E prostaglandins, which occur in ram semen, are likely to be formed by the vesicular glands and the ampulla of vas deferens in the sheep.

Comparative studies of acid and alkaline phosphatase activities in nonvascular smooth muscle membranes

Acid and alkaline phosphosphatase activities of subcellular fractions isolated from rat gastric muscle and vas deferens by differential centrifugation, sucrose density gradient and cation-induced aggregation methods were studied using p-nitrophenyl phosphate as the substrate. Alkaline phosphatase and a large portion of acid phosphatase activities were found to be of plasmalemmal origin. Acid and alkaline phosphatase activities were different in the effect of Mg2+, fluoride, vanadate, EDTA and resistance to heat inactivation suggesting that these two phosphatase activities were not expressed by the same enzyme.

Dipeptidyl peptidases in bovine reproductive organs and secretions

Dipeptidyl peptidases (DPP) I-IV were analysed in homogenates of bovine reproductive organs as well as in seminal vesicle secretions and seminal plasma. The presence of various molecular forms of these enzymes was studied by fractionation using gel filtration, anion exchange chromatography and chromatofocusing. The eluting enzymes were pooled, and their biochemical properties were briefly characterized. The histochemical localization of DPP II and IV was carried out with the most active tissues. DPP I and III were absent from seminal plasma, but their highest activity was found in the epididymis and increased during sexual maturation. DPP II was found mainly in a single molecular form and displayed a wide distribution in the reproductive organs. Its activity in seminal plasma may be derived from various organs, although the major sources are probably the apical activity in the epididymis, ampulla and seminal vesicle. DPP IV activity was high in the cauda epididymis, and ampulla, and in the seminal vesicles and their secretions. The high activity of DPP IV in seminal plasma appeared to derive from these organs, which showed a strong apical reaction of the epithelial lining. In seminal vesicles the enzyme was mainly secreted attached to membrane particles called vesiculosomes.

Opioid inhibition of adenylate cyclase in the striatum and vas deferens of the rat

The activity of adenylate cyclase in striatal membrane-enriched fractions (25,000 g) was inhibited by morphine, beta-endorphin, [D-Ala2-D-Leu5] enkephalin (DADLenk), fentanyl and bremazocine. Whereas guanosine triphosphate (GTP) appeared essential for the expression of this effect, sodium chloride seemed to enhance the degree of inhibition. Dopamine stimulation and sodium fluoride activation of the enzyme was also suppressed by morphine, beta-endorphin and DADLenk. beta-Endorphin and DADLenk inhibited adenylate cyclase activity in vasa deferentia membrane-enriched fractions (25,000 g); both opioids required GTP and NaCl and were inhibited by a delta-opioid receptor antagonist and by naloxone. Morphine, bremazocine and tifluadom did not significantly alter the activity of the vas deferens enzyme. Basal cyclic AMP values of striatal slices were not significantly altered by morphine, beta-endorphin or DADLenk. However, dopamine-induced elevation of cyclic AMP was reduced by morphine and this effect of the opiate was suppressed by naloxone. Only beta-endorphin lowered the basal cyclic AMP values in the vas deferens. The physiological relevance of adenylate cyclase coupling to opioid receptor subtypes is considered.