Temperature-dependent effects of the components of kallikrein-kinin system on sperm motility in vitro

Effect of captopril on semen quality

Various studies (direct and indirect) have presented the effect of captopril, a universally used antihypertensive medication, on semen quality; yet, this effect is still collectively unreviewed. This review systematically discusses and summarises the effect of captopril on semen quality. We searched all published articles in the MEDLINE electronic database since June 1985 until January 2016 using the keywords "captopril" and "sperm," and certain supporting articles were reviewed and considered, if relevant. In conclusion, up to the present time, captopril does not appear to induce a striking change in semen quality, and hence on male infertility, while it may affect the rate of spermatozoa-egg fusion as it inhibits the activity of angiotensin-converting enzyme that is released during capacitation and the acrosome reaction. Further research, mainly clinical, is still desired to prove these effects.

Effect of Bradykinin on Murrah buffalo (Bubalus bubalis) semen cryopreservation

Keeping in view the poor freezability of bubaline semen in conventionally used extenders, this study was conducted on three Murrah bulls to improve semen cryopreservation with the incorporation of Bradykinin (0.5, 1.0 and 2.0 ng ml(-1)) in routinely used egg yolk tris-glycerol (EYTG) extender. Bradykinin (2.0 ng ml(-1)) had significant (P<0.05) beneficial effect on live sperm % (81.6+/-1.8) and hypo osmotic swelling (HOS) % (63.0+/-1.3) as compared to their respective control values of 73.4+/-2.1 and 56.3+/-2.0 at 0 h post freezing. The post-thaw progressive sperm motility in semen samples diluted with EYTG containing 2.0 ng ml(-1) Bradykinin (65.5+/-1.4) was also significantly (P<0.01) higher than control (60.3+/-1.9) at 0 h post freezing. Thus incorporation of 2 ng ml(-1) Bradykinin in buffalo semen diluted in EYTG extender may be useful in improving the quality of cryopreserved bubaline semen.

Activity of testis angiotensin converting enzyme (ACE) in ejaculated human spermatozoa

Testicular angiotensin converting enzyme (ACE) isozyme is likely to play important functional roles in male reproduction. Several studies have shown that ACE is released from human spermatozoa during capacitation and that ACE is associated with reduced sperm motility. Recently, we established an assay to detect testicular ACE activity in human spermatozoa. The purpose of this study was to determine if testicular ACE activity is related to sperm motility in human ejaculates. Semen samples were collected from 80 infertile patients. According to the semen characteristics, they were divided into four (WHO) categories. Enzyme activities of ACE in spermatozoa (testicular ACE) and seminal plasma (somatic ACE) were spectrophotometrically determined. Total testicular ACE activity in spermatozoa was measured by solubilization of spermatozoa with Triton X-100. Membrane testicular ACE activity was measured in a sperm : PBS suspension. Sperm concentration and sperm motility were 136.6 +/- 154.1 x 10(6)/mL and 58.6 +/- 23.4%, respectively (mean +/- SD). Enzyme activities of membrane testicular ACE, total testicular ACE and somatic ACE were 0.273 +/- 1.219 microU/10(6) spermatozoa, 0.35 +/- 1.34 microU/10(6) spermatozoa and 684.7 +/- 226.6 mU/mL, respectively. A negative correlation was observed between sperm motility and membrane testicular ACE activity (p < 0.05). Membrane testicular ACE activity in 44 normal semen samples was 0.04 +/- 0.02 microU/10(6) spermatozoa, whilst that in 36 abnormal semen samples was 0.24 +/- 0.42 microU/10(6) spermatozoa. There was a significant difference between these two groups (p < 0.01). Membrane testicular ACE in sperm samples from normozoospermic men was significantly lower than that from oligoasthenozoospermic men (p < 0.05). These findings suggest that testicular ACE is released from normal functional spermatozoa for them to have fertilizing ability.

Effects of pentoxifylline on sperm motility in normogonadotropic asthenozoospermic men

Forty-seven normogonadotropic men with idiopatic asthenozoospermic were divided at random: group I (N = 22) received placebo and group II (N = 25) received 1200 mg of pentoxifylline/day during 6 months. Semen analysis was performed basal and at 3 and 6 months of the study period. No statistical changes in serum hormone concentration were found, nor in volume, sperm counts, viability, and morphology before and after treatment. Sperm motility increased following pentoxifylline treatment after 3 and 6 months from 25.5 (21.0-30.0) to 35.5 (31.5-39.0) (p < .00001) and to 42.0 (38.0-46.0) (p < .00001), respectively. Although in the placebo control cases some changes were observed in the sperm motility, they were less significant. Furthermore, progressive motility only in grade A increased with pentoxifylline from 2.5 (0.0-6.0) to 12.0 (6.0-19.5) (p < .001) at 3 months and to 22.5 (17.0-26.0) at 6 months (p < .00001). In conclusion, pentoxifylline had an additional effect rather than placebo and was useful treatment in these cases of male factor infertility.

The effect of bradykinin and the bradykinin antagonist Hoe 140 on kinematic parameters of human spermatozoa

Bradykinin (BK) has been suggested to be an active substance in the disputed therapeutic use of kallikrein to improve semen quality. The effects of exogenous BK and its antagonist Hoe 140, which acts on one of the bradykinin receptors (BK2), were examined in two groups of patients attending the fertility clinic: those with asthenozoospermia (group I) and normozoospermia (group II). Bradykinin (10nM-1 microM) added to washed human spermatozoa had no effect on most kinematic parameters and caused only a marginal increase (7%) in curvilinear velocity at 50 nM in group I patients; however, this increase was not suppressed by concomitant addition of the BK antagonist. The bradykinin antagonist itself had no effect on the percentage motility or kinematic motility parameters of washed human spermatozoa in either group of patients. The motility of spermatozoa in semen was also unaffected by the presence of the bradykinin antagonist. It is concluded that bradykinin does not act exogenously on washed spermatozoa nor endogenously on spermatozoa in semen to stimulate motility via BK2 receptors, regardless of the initial quality of the sperm motility.

Complexes of tissue kallikrein with protein C inhibitor in human semen and urine

An ELISA was developed for quantifying the complex between tissue kallikrein (tKK) and protein C inhibitor (PCI) (tKK:PCI) in seminal plasma and urine. The ELISA used purified tKK:PCI complex as a standard and was specific for this complex with a detection limit of about 1.1 pM. Purified tKK:PCI complex was obtained from human urine and was 95% homogeneous as judged by SDS/PAGE. The 90-kDa band corresponding to the purified tKK:PCI complex reacted with anti-tKK and anti-PCI antibodies as judged by immunoblotting. Seminal plasma collected in the absence of extrinsic inhibitors contained 1.8 +/- 0.6 nM tKK:PCI complex and 4.7 +/- 2.8 nM immunoreactive tKK (mean +/- SD, n = 10), which indicates that about 28% of the total tKK immunoreactivity is forming complexes with PCI. When semen was collected in the presence of tKK inhibitors it had only about 6% of the tKK complexed to PCI. In vitro studies showed that the tKK:PCI complex formation in semen was accomplished in about 1 h and that heparin stimulated both the rate and the extent of complexation of tKK with PCI. Native urine showed low levels of tKK:PCI complex, but after dialysis urine had 0.17 +/- 0.05 nM complex. Formation of tKK:PCI complex in urine and semen was also demonstrated by immunoblotting. These results suggest that PCI is a physiological inhibitor of tKK and provide additional evidence of the involvement of PCI in human reproduction.

The enzymatic degradation of bradykinin in semen of various species

The degradation of bradykinin in semen and on washed sperm cells of various species (human, pig, cattle, sheep) is mainly controlled by two peptidases, the angiotensin-converting enzyme (ACE/kininase II; E.C. 3.4.15.1) and neutral metalloendopeptidase (NEP; E.C. 3.4.24.11). In addition, minor activities of kininase I (carboxypeptidase N/CPN; E.C. 3.4.17.3) were measured exclusively in human samples. Samples of the investigated species varied considerably in their ratios of the activities of bradykinin degrading peptidases. This should be considered in any approach aimed at maintaining the promoting effect of bradykinin on sperm motility by use of enzyme inhibitors.

Olfactory receptors are displayed on dog mature sperm cells

Olfactory receptors constitute a huge family of structurally related G protein-coupled receptors, with up to a thousand members expected. We have shown previously that genes belonging to this family were expressed in the male germ line from both dog and human. The functional significance of this unexpected site of expression was further investigated in the present study. We demonstrate that a few dog genes representative of various subfamilies of olfactory receptors are expressed essentially in testis, with little or no expression in olfactory mucosa. Other randomly selected members of the family show the expected site of expression, restricted to the olfactory system. Antibodies were generated against the deduced amino acid sequence of the most abundantly expressed olfactory receptor gene in dog testis. The purified serum was able to detect the gene product (DTMT receptor) in late round and elongated spermatids, as well as in the cytoplasmic droplet that characterizes the maturation of dog sperm cells, and on the tail midpiece of mature spermatozoa. Western blotting further confirmed the presence of a 40-kD immunoreactive protein in the membrane of mature sperm cells. Altogether , these results demonstrate that the main expression site of a subset of the large olfactory receptor gene family is not olfactory mucosa but testis. This expression correlates with the presence of the corresponding protein during sperm cell maturation, and on mature sperm cells. The pattern of expression is consistent with a role as sensor for unidentified chemicals possibly involved in the control of mammalian sperm maturation, migration, and/or fertilization.

Possible effects of the kallikrein-kinin system on male reproductive functions

All four components of the kallikrein-kinin system--kininogens, tissue kallikreins, kinins, and kininases--have been found in human male genital secretions. Kinins are continuously released from seminal plasma kininogens through limited proteolysis by kininogenases like tissue kallikrein from prostate and sperm acrosin. Kinins are the terminal effectors of the kallikrein-kinin system and increase sperm motility and sperm metabolism at nanomolar concentrations. Recent investigations indicate that these effects are possibly mediated by a specific sperm membrane integrated bradykinin receptor, subtype B2. The two major kininase that are present in seminal plasma are kininase II and neutral metallo-endopeptidase. Kininase II, which is identical with angiotensin-converting enzyme, is also involved in the renin-angiotensin system as it converts angiotensin I into angiotensin II and thus is the connecting enzyme of both systems. Apart from the observed effects of kinins on sperm motility, the kallikrein-kinin system is thought to be involved in the regulation of spermatogenic functions of the testis: in the rat, kallikrein activates Sertoli cell function, increases the relative number of spermatocytes and the [3H] thymidine incorporation of testicular tissue, enhances glucose-intake, and increases testicular blood flow. Clinical trials showed that systemic administration of kallikrein may be particularly useful for treatment of infertile men suffering from asthenozoospermia and/or oligozoospermia. During kallikrein therapy, the number of spermatozoa and both quantitative and qualitative sperm motility increased, and a significant improvement of the conception rate was achieved. An increased sperm number was also observed after application of the specific kininase II inhibitor captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of theophylline to enhance sperm function

Poor sperm motility is an important factor in male infertility. Preliminary results in our laboratory on a group of 19 men (10 suspected infertile men and 9 fertile donors) showed stimulation of sperm fertilizing ability after sperm washing with theophylline as demonstrated by zona free hamster egg penetration test. The egg penetration rate for the control spermatozoa samples from subfertile men was 16%. Incubation with theophylline (10 mM) increased the penetration rate to 46%, whereas semen incubation with theophylline (20 mM) increased the penetration rate to 51%. A similar twofold increase in egg penetration was observed in the semen of fertile men incubated with theophylline of similar concentrations. Subfertile patients with ejaculate volumes of less than or equal to 1 ml or total motile sperm count of less than or equal to 10 x 10(6)/mL or increased semen viscosity did not exhibit beneficial effects with theophylline washing as measured by hamster egg penetration test score. The increase in percentage of penetrated eggs with theophylline use in both fertile and subfertile men was significant at 10 mM concentration (p less than .001) and 20 mM (p less than .001) when compared to control (untreated) samples. No significant difference in penetration rate was seen between 10 and 20 mM theophylline concentrations. It appears that theophylline may be useful in improving the fertilizing capacity of selected human semen samples with poor motility and poor penetration ability under artificial insemination conditions.

Effect of Sp-cAMP on sperm motility in patients with unexplained infertility

Sperm motility is one of the most important semen parameters affecting the fertility of an individual. Sp-cAMP, a thiophosphate analogue of c-AMP, is a phosphodiesterase inhibitor controlling the intracellular c-AMP levels which in turn influences sperm motility. The results in our laboratory on a group of suspected subfertile men and fertile donors showed significant enhancement of sperm motility after incubation of washed sperm with various doses of Sp-cAMP.

Investigations on the influence of bradykinin upon the motility of ram spermatozoa

The influence of bradykinin, a component of the kallikrein-kinin system, on the motility of ram spermatozoa was examined in vitro (photometric motility evaluation, penetration test in cervical mucus of sheep, estimation of the percentage of forward-moving spermatozoa in the thermal resistance test). Whereas the motility was found to be influenced by bradykinin the acrosomal status remained undisturbed by it. With fresh as well as with frozen semen, the drug mainly increased the motility of samples with a low initial motility. With frozen semen, the penetration test revealed greater motility rises at 22 degrees C than at 38 degrees C. The importance of the results in relation to the angiotensin-converting enzyme (kininase) as well as the motility evaluation capabilities of the methods used are discussed. There was, however, no positive drug effect after adding the drug in the course of cryopreservation prior to freezing semen in straws although bradykinin solutions frozen in liquid nitrogen maintained their effectiveness.

Angiotensin-converting enzyme and other peptidolytic enzymes in human semen and relations to its spermatologic parameters

Angiotensin-converting enzyme (ACE) and other enzymes of the renin-angiotensin system (RAS) occur in human semen in high activities. In contrast to bull ejaculates, not all zinc-dependent metallopeptidases are found to be in close correlation to the microscopically determined semen parameters; such a relationship was established only partly for the ACE. On the other hand, the RAS-dependent spermatozoa-bound enzymes, inclusive ACE, uniformly show negative correlations to the spermatologic parameters of human semen. These results, for the first time, point to different functions of the sperm-cell-bound (testicular) and of the seminal plasma (pulmonary) ACE activities.

Occurrence and potential importance of angiotensin-converting enzyme in semen of boars

The activities of angiotensin-converting enzyme (ACE) and leucinaminopeptidase (LAP) are positively correlated with corresponding concentrations of sperm cells in semen of boars kept under normal conditions. The spermatozoa bound ACE activity, in general, does not reflect differences in the quality of semen (bull and boars). On the other hand, the ACE activity directly bound on the sperm cells is significantly elevated, if 'exogenic noxes' (by feeding or keeping) influence the fertility of boars in a drastic manner. These results are discussed with regard to the differential diagnostic importance for estimating the semen quality and to the causal relations between increased enzyme binding and injury of sperm cells.

Comparison of motility stimulants for cryopreserved human semen

Caffeine, pentoxifylline, 2-deoxyadenosine, cyclic adenosine monophosphate (cAMP), relaxin, adenosine, kallikrein, and calcium were compared for their ability to stimulate motility of cryopreserved sperm. Caffeine, pentoxifylline, and 2-deoxyadenosine significantly increased the percentage of motile sperm at 15, 30, 45, and 60 minutes after administration. Sperm velocity was significantly increased by caffeine at 0, 15, 30, and 45 minutes, and by pentoxifylline at 0, 45, and 60 minutes. Consistent stimulation was not observed for other chemicals. Caffeine, pentoxifylline, and 2-deoxyadenosine were then examined for their ability to provide motility stimulation after removal with washing. With the exception of caffeine, percent motility and velocity for stimulated and untreated sperm were similar after washing. A significant reduction in motility was observed at 48 hours after washing for caffeine. The percentage of hamster oocytes penetrated at 24 hours after washing was significantly reduced for caffeine, 2-deoxyadenosine, and pentoxifylline combined with 2-deoxyadenosine. Pentoxifylline-treated sperm showed no reduction in fertilizing capacity. These results indicate that, of the chemicals examined, pentoxifylline is superior for motility stimulation of cryopreserved sperm.