Arginine uptake by rabbit spermatozoa

Success in the acquisition of Bombyx mori sperm motility is influenced by the extracellular production of nitric oxide (NO) in the presence of seminal fluid nitric oxide synthase (NOS)

A trypsin-like protease called initiatorin is known to initiate sperm motility in the silkworm, Bombyx mori, but little is known about the signaling events leading to sperm flagellar beating. The aim of this study was to investigate whether this mechanism of sperm motility activation involves the signaling transmitter nitric oxide (NO). NO is produced from the amino acid L-arginine by the enzyme action of nitric oxide synthase (NOS; EC 1.14.13.39). Simple treatment of quiescent sperm with an NO donor (SNAP or NOC7) in vitro did not lead to activation of motility. Nevertheless, initiatorin- or trypsin-induced motility was blocked by pretreatment of sperm with either the NOS inhibitor L-NAME or NO scavenger carboxy-PTIO. These observations suggested that NO may play important physiological roles in the acquisition of sperm motility under the in vitro condition used here. Then, we investigated whether NO synthesis would occur in the spermatophore, a capsule containing spermatozoa that is created by the contents of various male reproductive glands and is the site of sperm maturation. The amounts of NO₂^- and NO₃^-, stable metabolites of NO, reached maximum values after enclosure in the spermatophore, a time when apyrene spermatozoa acquire vigorous motility. Moreover, RT-PCR and Western blotting analyses of NOS indicated that it is abundantly expressed in glandula (g.) lacteola of the virgin male ejaculatory duct, from which it is secreted to the seminal fluid and transferred to the female during mating. Previous studies demonstrated that free L-arginine is supplied de novo by a specific proteolytic reaction in which initiatorin participates during spermatophore formation (Osanai et al., 1987c). Based on these results, it can be presumed that the mixing of seminal fluid contents from each male reproductive organ during ejaculation induced NO production outside of the spermatid, and exogenous NO stimulated a signaling pathway involved in the activation of silkworm apyrene sperm.

Effect of Myoinositol and Antioxidants on Sperm Quality in Men with Metabolic Syndrome

This prospective longitudinal study investigated the effects of a dietary supplement in patients affected by reduced sperm motility (asthenospermic males) with metabolic syndrome. The product tested was Andrositol®, which contains myoinositol (MI) as principal compound, in association with other molecules, and the parameters evaluated were semen characteristics as well as hormone and metabolic profiles. The inclusion criteria were subjects aged over 18 years, with asthenospermia and metabolic syndrome. The exclusion criteria were presence of cryptorchidism, varicocele, and prostatitis. For this study, 45 males who had such features were enrolled. Their selection was made according to the 2010 World Health Organization (WHO) criteria (5th Edition) for the Evaluation of Human Semen. Hormone and metabolic profiles and semen parameters were assessed at the beginning of the study and after three months of treatment with Andrositol. The differences between the values before and after the supplementation were found statistically significant. Andrositol normalized the metabolic profile of these patients, improving their insulin sensitivity. Moreover, testosterone levels were increased and the semen characteristics, such as sperm concentration, motility, and morphology, highly improved. In conclusion, the association of MI with other molecules (micronutrients and vitamins) could be an effective therapy for metabolic disorders, as well as hormonal and spermatic changes responsible for male infertility.

Identification of NO induced and capacitation associated tyrosine phosphoproteins in buffalo (Bubalus bubalis) spermatozoa

To acquire the fertilizing competence, spermatozoa must undergo a cascade of physiological and biochemical changes collectively defined as capacitation. Compelling evidence signifies that the global increase in protein tyrosine phosphorylation is the driving factor for capacitation. In our laboratory, we previously demonstrated that nitric oxide (NO) induces capacitation in buffalo sperm and is associated with an increase in protein tyrosine phosphorylation. The aim of the present study is to identify the proteins undergo tyrosine phosphorylation during NO induced buffalo sperm capacitation using 2-D immunoblotting and mass spectrometry. The percentage of progressively motile and capacitated sperm was more in presence of l-arginine. Along with known tyrosine phosphoproteins like ATP synthase subunit beta, pyruvate dehydrogenase E1 component subunit beta, GST mu 3, F-actin capping protein subunit beta 2, GPD2 and VDAC2, interestingly novel tyrosine phosphoprotein substrates such as actin, serine/threonine-protein phosphatase PP1-gamma catalytic subunit, and glutamine synthetase were also identified which might be specific to the NO induced signaling and also emphasizes the species specificity with respect to tyrosine phosphorylation of proteins during capacitation. In conclusion, this study forms an essential step in delineating the proteins undergo tyrosine phosphorylation in response to NO induced signaling pathways during capacitation of buffalo sperm.

Arginine activates glycolysis of goat epididymal spermatozoa: an NMR study

The present study explores the mechanism underlying the action of L-arginine on the metabolic activity of spermatozoa. Goat epididymal spermatozoa were incubated with different concentrations of L-arginine to determine its effect on the utilization of glucose, fructose, and pyruvate. NMR techniques have been applied to elucidate the effect of L-arginine, L-lysine, and L-ornithine on the glycolysis of epididymal goat spermatozoa. Whereas 31P NMR has been used to estimate the change of pH in the presence of different concentrations of L-arginine, 13C NMR has been used to estimate the substrate consumption and lactate production. At optimal concentration of L-arginine, the forward metabolic rates have been found to increase by two to three times over control experiments. Arginine is not consumed in these reactions, but acts as an activator. Longitudinal relaxation time (T1) measurements indicate that the guanidino group of L-arginine plays an active role in binding to cells. The amino acid L-lysine is less effective, and L-ornithine is ineffective.

Transport of methionine in sea-urchin sperm by a neutral amino-acid carrier

A carrier-mediated transport for L-methionine and other neutral amino acids exists in sperm of the sea urchin Lytechinus pictus. The initial rate of L-methionine entry is a Michaelis-Menten function of the methionine concentration in the external medium. The maximum velocity is low [V = 250 pmol h-1 (10(9) sperm)-1 at 22 degrees C] and the affinity is high (Km = 6-10 microM). The initial rate of transport under steady-state exchange conditions is also a Michaelis-Menten function of the external concentration of methionine. The Km determined by this method is about 14 microM. Neutral amino acids compete with L-methionine transport as shown by initial velocity measurements. These results indicate that L-methionine transport is a carrier-mediated process. The temperature dependence of the process is approximately 84 kJ (20 kcal) mol-1 K-1, which is not compatible with a simple diffusion mechanism, but in the range of values usually found for a mediated transport. The transport is largely Na+-independent and does not depend on Ca2+, K+ or H+ gradients. It is only partially sensitive to KCN, showing it is mainly independent of oxidative phosphorylation. The steady-state internal methionine concentration is not a linear function of the external amino acid concentration. This suggests that an exit by diffusion competes with a carrier-mediated concentrative transport in a cellular compartment. This mediated transport is compared to those of higher animal cells.