Enzyme activities in fish spermatozoa with focus on lactate dehydrogenase isoenzymes from herring Clupea harengus

Effects of dietary supplementation of multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of rainbow trout (Oncorhynchus mykiss) broodstock spermatozoa

The present experiment aims to study the effects of dietary multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of male rainbow trout. For this purpose, a total of 48 broodstocks with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 10⁹ (P1), 2 × 10⁹ (P2), and 4 × 10⁹ (P3) CFU probiotic kg^-1 diet for 12 weeks. Results showed that dietary supplementation of probiotics significantly increased plasma testosterone level, motility time of spermatozoa, sperm density, and spermatocrit value in P2 and P3 treatments and Na⁺ level in P2 treatment compared to the control group (P < 0.05). The activities of aspartate aminotransferase and lactate dehydrogenase had significantly decreased in the P2 treatment compared to the control group (P < 0.05). No considerable variations were observed between control fish and treatment groups (P > 0.05) in semen biochemical parameters, percentage of motile spermatozoa, osmolality, and pH of seminal plasma. Based on the results, the highest fertilization rate (97.2 ± 0.9%) and eyed egg survival (95.7 ± 1.6%) were observed in the P2 treatment, and those values showed remarkable differences with the control group (P < 0.05). The results indicated that multi-strain probiotics have potential efficacy on semen quality and fertilization ability of rainbow trout broodstock spermatozoa.

Bioenergetics of fish spermatozoa with focus on some herring (Clupea harengus) enzymes

Herring (Clupea harengus) shows the unique behavior of reproductive biology in which spermatozoa remains in the surrounding media for extended periods. It is an excellent model for studying the malic enzyme (ME) and creatine kinase (CK) biochemical properties because of their high activity and variability of molecular isoforms. The specific activity of NAD-preferring ME in herring spermatozoa is the highest among other fish spermatozoa and is localized in its large mitochondrion. Two different CK isoforms, dimer and octamer, were detected in herring spermatozoa. It has already been shown that CK isoforms play an important role in energy homeostasis by catalyzing a reversible transfer of the phosphate of ATP to creatine to yield ADP and creatine phosphate (CP) (creatine/CP circuit). Two lactate dehydrogenase (LDH) isoenzymes were also shown in herring spermatozoa, LDH-B4 and LDH-A2B2. In this mini-review, the role of ME and energy transport system with easily diffusible creatine and CP in herring spermatozoa is discussed.

Sperm quality in fish: Determinants and affecting factors

Fish sperm quality assessment is helpful for optimizing production and for monitoring the environmental state. Sperm can be monitored relatively easy and, to date, various analyses have been applied and proven to be helpful in this task. Among them, sperm motility parameters such as sperm speed are one of the main performance traits during assisted fish reproduction. Apart from motility the sperm concentration, volume, and seminal plasma pH and osmolality are also frequently evaluated and are the main sperm quality indicators measured in fish sperm. However, other parameters also determine sperm fertilization potential. Recent knowledge reveals several additional parameters of high importance for sperm function. Among them are DNA integration, membrane stability, mitochondria status and enzymatic activity. Measuring all these parameters in fish sperm provides complex knowledge regarding male fertility and helps to improve broodstock maintenance protocols as well as gamete handling and fertilization processes. This review focuses on the presentation of the sperm quality measures for freshwater and marine species of the fish and provides information regarding recent methods of sperm quality evaluation.

NAD-preferring malic enzyme: localization, regulation and its potential role in herring (Clupea harengus) sperm cells

Herring spermatozoa exhibit a high activity of NAD-preferring malic enzyme (NAD-ME). This enzyme is involved in the generation of NADH or NADPH in the decarboxylation of malate to form pyruvate and requires some divalent cations to express its activity. In order to confirm that NAD-ME isolated from herring sperm cells is localized in mitochondria, we performed immunofluorescent analysis and assayed spectrophotometrically the malic enzyme reaction. Production of polyclonal rabbit antibodies against NAD-ME from herring spermatozoa enabled identification of mitochondrial localization of this enzyme inside herring spermatozoa. The kinetic studies revealed that NAD-ME was competitively inhibited by ATP up to tenfold. Addition of fumarate reversed ATP-dependent inhibition of NAD-ME to 55 % of its maximum activity. The pH-dependent regulation of malic enzyme activity was also examined. Malic enzyme showed maximum activity at pH near 7.0 in all studied conditions. Finally, the role of malic enzyme activity regulation in mitochondria of herring sperm cells was discussed.

Biomarkers of Cytotoxic, Genotoxic and Apoptotic Effects in Cyprinus carpio Exposed to Complex Mixture of Contaminants from Hospital Effluents

Hospital wastewater is an important source of emerging contaminants. Recent studies emphasize the importance of assessing the effects of mixtures of contaminants rather than environmental risk of their individual components, as well as the determination of intrinsic toxicity of wastewater. Mixtures of pollutants has possible interactions that have notable environmental side effects. The aim of this study is an attempt to characterize biomarkers in Cyprinus carpio related to the exposure to a complex mixture of contaminants found in hospital wastewater. Results of a particular hospital effluent show the presence of traces of heavy metals, high chlorine concentration and emerging contaminants such as non-steroidal anti-inflammatory drugs. The LC50 was of 5.49 % at 96 h. The cytotoxic, genotoxic and apoptotic biomarkers increase when fishes were exposed to wastewater (1/10 CL50) from hospital wastewater. This study emphasizes the importance of identifying and quantifying the effects of contaminants as pharmaceuticals, disinfectants and surfactants in order to design and implement an ecotoxicological plan.

Sperm traits in farmed and wild Atlantic salmon Salmo salar

Differences in sperm metabolism and morphology between wild and non-local farmed Atlantic salmon Salmo salar were assessed by measuring metabolic enzyme activities and length of sperm flagella. No differences were observed between wild and farmed S. salar sperm with regards to cell counts or any of the biochemical variables assessed. Flagella of sperm cells were significantly longer in wild than farmed S. salar; however, this did not result in higher energy levels or different fertilization rates.

Purification and properties of malic enzyme from herring Clupea harengus spermatozoa

Herring spermatozoa exhibit higher activity of malic enzyme (ME) than Atlantic salmon (Salmo salar), brown trout (Salmo trutta), carp (Cyprinus carpio) and African catfish (Clarias gariepinus) spermatozoa. Two molecular forms of ME are present in herring spermatozoa: an NAD-preferring malic enzyme with very high activity and an NADP-specific malic enzyme with much lower activity (ratio about 33:1). NAD-preferring ME was purified by chromatography on DEAE-Sepharose, Red Agarose and Sephadex G-200 to a specific activity of 36 μmol/min/mg protein and NADP-specific ME on DEAE-Sepharose and 2'5'-ADP Sepharose. The molecular mass for NAD-preferring and NADP-specific ME determined by SDS-PAGE was equal to 61 and 64 kDa, respectively. High activity of ME suggests adaptation of herring spermatozoa to metabolism at high oxygen tension for herring spawn.

Enzymatic activities in spermatozoa and butyltin concentrations in Baltic turbot (Scophthalmus maximus)

Spermatozoal enzymes of fish (NAD+- and NADP-dependent dehydrogenases and creatine kinase (CK)) were previously determined to be sensitive to tributyltin (TBT) in laboratory experiments and were thus indicated for use as biomarkers for TBT exposure. However, the potential ability of spermatozoal enzymes as biomarkers of TBT exposure has never been recapitulated in a field study. For this purpose, the kinetic activities of spermatozoal enzymes of the natural turbot Scophthalmus maximus population from the Gulf of Gdańsk (GDA) and the Pomeranian Bay (POM) in the southern Baltic Sea were measured. Gas chromatography/high-resolution mass spectrometry was used to determine the concentrations of TBT and its breakdown products, dibutyltin (DBT) and monobutyltin (MBT), in the muscle, liver and testes of the male turbot. Males from GDA had significantly higher enzymatic activities and butyltin (BT) content in tissues than those from POM. A general linear model (GLM) showed that lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PDH) and CK activities increased significantly with BT concentration in the testes and liver. We indicate the potential effects of TBT pollution on the spermatozoal enzymes of Baltic turbot.

Comparative protein profiles: potential molecular markers from spermatozoa of Acipenseriformes (Chondrostei, Pisces)

Sturgeon and paddlefish (Acipenseriformes), the source of roe consumed as caviar, are a unique and commercially valuable group of ancient fishes. In this study, comparative proteomics was used to analyze protein profiles of spermatozoa from five sturgeon species and one paddlefish: Siberian sturgeon (Acipenser baerii), sterlet (A. ruthenus), Russian sturgeon (A. gueldenstaedtii), starry sturgeon (A. stellatus), beluga (Huso huso), and Mississippi paddlefish (Polyodon spathula). Protein profiles of spermatozoa were determined by isoelectric focusing and two-dimensional electrophoresis (2-DE) high-resolution gels. The peptides, previously selected by 2-DE analysis as potentially species-specific, were obtained by "in-gel" tryptic digestion, followed by matrix-associated laser desorption/ionization time-of-flight/mass spectrometry (MALDI-TOF/MS). Among the 23 protein spots selected, 14 were identified as isoforms of enolase B present in all species, but with different isoelectric points or molecular mass. Exceptions were A. ruthenus and H. huso, species with a close phylogenetic relationship. Glycerol-3-phosphate dehydrogenase was detected exclusively in P. spathula. Phosphoglycerate kinase was detected only in A. ruthenus and H. huso, and 3 additional proteins (fructose bisphosphate aldolase A-2, glycogen phosphorylase type IV and glyceraldehyde-3-phosphate dehydrogenase) were found exclusively in A. gueldenstaedtii and H. huso. This study points to the application of proteomics for differential characterization and comparative studies of acipenseriform species at the molecular level.

In vitro effect of produced water on cod, Gadus morhua, sperm cells and fertilization

The in vitro effect of produced water released by oil and gas platforms was assessed by exposing cod sperm cells to realistic concentrations of this mixture (100, 200, 500 ppm). We investigated produced water impact on enzymes of the aerobic (citrate synthase) and glycolytic metabolism (lactate dehydrogenase), lipid catabolism (lipase), as well as an anti-oxidant enzyme (catalase). Fertilization rates, viability, respiration, ATP, and total motility duration were also evaluated. To explore correlations between these parameters, we have also tested the effect of conserving sperm for 24 h at 4 degrees C. After conservation, fertilization success was decreased but other parameters were not affected. Produced water did not result in a significant change in fertilization; a significant increase in sperm protein amounts and citrate synthase activity can be observed. No correlations are found between parameters showing that sperm viability and unchanged energy levels do not translate into equivalent fertilization capacity. To conclude, exposure of sperm to produced water resulted only in subtle effects on cells. These findings bring information on the effect of produced water on sperm itself rather than on spermatogenesis or testis development of an exposed fish.

Bioenergetics of fish spermatozoa during semen storage

This mini-review focuses on changes in ATP and creatine phosphate concentrations in fish sperm under storage conditions. The storage of catfish sperm at 4 degrees C leads to ATP depletion and decreased sperm motility. The rate of intracellular ATP depletion can be diminished through the addition of energetic substrates to the sperm storage medium, with lactate + pyruvate being the most efficient substrates for maintaining ATP concentrations in catfish sperm. The decrease in ATP concentration is closely associated with increases in AMP and hypoxanthine content. In contrast to catfish sperm, carp sperm is able to maintain intracellular ATP concentration close to the physiological level during storage. Collectively, these results suggest that fish species differ in terms of the energy metabolism of their spermatozoa and that the semen storage medium must be carefully selected for a particular fish species so as to maintain the ATP concentration and adenylate energy charge close to physiological values as long as possible.

Do territorial male three-spined sticklebacks have sperm with different characteristics than nonterritorial males?

The three-spined stickleback ( Gasterosteus aculeatus aculeatus L., 1758) shows unequal energetic expenditure upon reproduction as some males defend territories and build nest (territorials: TM) where they spawn singly with females, whereas other males remain nonterritorial (NTM), do not build nests, and resort to sneaking fertilizations from nesting males. We examined the effects of reproductive strategy on various sperm parameters. Territorial status was assessed by introducing males in small wading pools and recording the number of males with a nest. Males from all pools were remixed and nesting status was reassessed. This allowed us to discriminate a group of males with repetitive territorial or nonterritorial behaviours (TM and NTM) or a “facultative” territorial behaviour (FM). TM had a significantly larger gonadosomatic index (GSI) than both FM and NTM. FM had a GSI that was significantly larger than NTM, but significantly smaller than TM. Sperm motility did not differ among males with different reproductive tactics. There were no significant differences in citrate synthase (CS) and pyruvate kinase (PK) activities among males with different status. Curiously, we found a significant negative relationship between CS and PK activities and total number of sperm.

Sperm proteins in teleostean and chondrostean (sturgeon) fishes

Sperm proteins in the seminal plasma and spermatozoa of teleostean and chondrostean have evolved adaptations due to the changes in the reproductive environment. Analysis of the composition and functions of these proteins provides new insights into sperm motility and fertilising abilities, thereby creating possibilities for improving artificial reproduction and germplasm resource conservation technologies (e.g. cryopreservation). Seminal plasma proteins are involved in the protection of spermatozoa during storage in the reproductive system, whereas all spermatozoa proteins contribute to the swimming and fertilising abilities of sperm. Compared to mammalian species, little data are available on fish sperm proteins and their functions. We review here the current state of the art in this field and focus on relevant subjects that require attention. Future research should concentrate on protein functions and their mode of action in fish species, especially on the role of spermatozoa surface proteins during fertilisation and on a description of sturgeon sperm proteins.

Inhibition by tributyltin of herring skeletal muscle lactate dehydrogenase activity

The activity of herring (Clupea harengus) skeletal muscle lactate dehydrogenase (EC 1.1.1.27) LDH-A4 isoenzyme was examined in the presence of tributyltin chloride (TBT). This paper reports the in vitro inhibition of LDH activity with increasing concentration of TBT. Bovine serum albumin (BSA) added to the LDH-A4 isoenzyme prior to the addition of TBT was able to protect enzyme activity against inhibition by this toxicant. The observed protection of LDH-A4 activity increased with increasing BSA concentration in the incubation medium. The results suggest that the presence of BSA could protect LDH activity from direct binding of TBT to LDH.

Quantitative determination of creatine kinase release from herring (Clupea harengus) spermatozoa induced by tributyltin

Creatine kinase (CK, ATP creatine phosphotransferase, EC 2.7.3.2) is an enzyme participating in ATP regeneration, which is the primary source of energy in living organisms. We demonstrated that CK from herring spermatozoa has high activity ( approximately 452 micromol/min/g of fresh semen) and has a different electrophoretic mobility from isoenzymes present in skeletal muscle. In our study, we investigated toxic effect of tributyltin (TBT) on herring spermatozoa using a specific sperm viability kit to observe live and dead sperm cells with a confocal microscope. Treatment of herring spermatozoa with TBT caused a time-dependent decrease of viability: 35% nonviable cells with 5 microM TBT and more than 90% nonviable cells with 10 microM TBT after 6 h exposure. We also monitored CK release from damaged spermatozoa into surrounding medium containing different concentrations of TBT. The higher concentration of TBT was used the more CK release from spermatozoa was observed. We suggest that CK could be a good biomarker of sperm cell membranes degradation in the case when lactate dehydrogenase release from permeabilized cells is not possible for rapid determination of the effect of TBT.