Effect of angiotensin converting enzyme (ACE) and angiotensins on human sperm functions.

The presence of components of the renin angiotensin system (RAS) and specific receptors of angiotensin II in the female and male reproductive tract supports the hypothesis that reproductive functions may be controlled by RAS. Therefore, the present study investigated the influence of ACE and angiotensins on sperm functions and the sperm-egg interaction. The experiments did not indicate direct effects of ACE on the capacitation process or acrosome reaction. Release of ACE from human spermatozoa during capacitation was not related to their ability to undergo acrosome reaction after stimulation with ionophore. Therefore, ACE release does not seem to be a useful clinical marker for human sperm capacitation. However, decreased binding of human spermatozoa to the oolemma of zonafree hamster oocytes after inhibition of ACE by captopril indicates that kininase II is involved in sperm-egg interactions. In contrast to other studies, incubation with captopril had no influence on sperm binding to the zona pellucida. Because effects of ACE on sperm-egg interactions but not on capacitation or acrosome reaction were observed, several experiments were performed to study the influence of substrates and products on the acrosome reaction. Angiotensin II induced the acrosome reaction dose-dependently, whereas angiotensin I had no effect on the acrosome reaction. The effect of angiotensin II on acrosome reaction seems to be calcium-dependent and mediated by protein kinases. Since a specific type 2 angiotensin II receptor inhibits the acrosome reaction induced by angiotensin II, this subtype of receptors may be present at the surface of sperm heads. Another clue for the presence of type 2 receptors on human spermatozoa is the finding that pertussis toxin did not inhibit the angiotensin II induced acrosome reaction. In contrast to type 1 angiotensin II receptors, type 2 receptors are known to be G-protein independent.

Influence of urogenital infections on sperm functions.

Many studies have examined the impact of genital tract infections on male fertility; however, the effect of bacteriospermia on sperm quality is still controversial. Bacterial infections are more frequently found in semen samples from asymptomatic infertile patients than in those from fertile men. Bacteriospermia is also a common problem of male partners from couples undergoing IVF. Therefore, the effects of microorganisms on human sperm acrosome reaction of oocytes have been studied in vitro and in vivo. Incubation of spermatozoa with Escherichia coli or Mycoplasma hominis in vitro resulted in reduced sperm motility and inducibility of acrosome reaction (delta AR) after exposure to calcium ionophore A23187. To show possible effects of E. coli and mycoplasma species on sperm functions in vivo, data from 488 patients were evaluated, in whose ejaculates microbiological examinations and determinations of acrosome reaction after exposure to low temperature had been performed. U. urealyticum and E. coli were found in semen samples from 52 and 31 men, respectively. M. hominis was only present in a minor number of samples and was not included in this study. Semen concentrations of E. coli and U. urealyticum ranged between 500-100,000 cfu x ml-1 and 100-80,000 cfu x ml-1. No correlation was found between delta AR and concentration of bacteria (Spearman rank correlation coefficient, E. coli: r-0.081, P = 0.6644; U. urealyticum: r = -0.081, P = 0.5698). In 69% of cases with U. urealyticum infection and reduced inducibility of acrosome reaction, this sperm function was normal after antibiotic therapy. However, improvement of acrosomal function may only be due to intra-individual variations of acrosome reaction. While E. coli and mycoplasma species affect sperm functions in vitro, the present data and a review of the literature fail to demonstrate similar effects in vivo.

In vitro effect of Escherichia coli on human sperm acrosome reaction.

Escherichia coli are known to reduce human sperm motility. The purpose of the present study was to examine whether these bacteria may also affect the acrosome reaction, which is another important sperm function. The acrosome reaction was determined in spermatozoa from 29 fertile men by triple stain after 3-h incubation at 37 degrees C with 2 x 10(6) E. coli/mL or without bacteria (control). Each sample was treated with 0.1% DMSO (spontaneous acrosome reaction) or calcium ionophore A23187 (induced acrosome reaction) for 1 h at 37 degrees C. The inducibility of the acrosome reaction was significantly lower in semen samples pretreated with E. coli than in the control samples (9.8 +/- 4.2% vs. 12.7 +/- 5.3%; p < .05). The results demonstrate that E. coli affect the inducibility of the acrosome reaction in vitro and may impair the fertilizing capacity of human spermatozoa.

Andrological work-up of patients undergoing microsurgical epididymal sperm aspiration or testicular sperm extraction.

Microsurgical epididymal sperm aspiration (MESA) and testicular sperm extraction (TESE) require close cooperation between andrologists, urologists and gynaecologists. Intracytoplasmic sperm injections were established in Giessen in March 1994 and embryo transfer (ET) was performed in 342 of 375 patients (91.2%). The percentage of pregnancies and ongoing pregnancies are 35.4% per ET (32.3% per cycle) and 25.1% per ET (22.9% per cycle), respectively. Microsurgical procedures such as epididymovasostomy or vasovasostomy and cryopreservation of human semen are also established methods. The purpose of the present study was to describe the andrological work-up for patients before MESA and TESE. Experiments demonstrate that incubation of testicular tissue samples in IVF medium and treatment with 1 mg ml-1 pentoxifylline increase the number of extracted motile spermatozoa. Centrifugation of the medium results in a further concentration of sperm cells. If no motile spermatozoa can be found in the supernatant medium, they may be extracted directly from the testicular tissue samples by means of a micromanipulator.

The effect of smoking and varicocele on human sperm acrosin activity and acrosome reaction.

Smoking and varicocele are frequent findings in the medical history and physical examination of patients attending andrological outpatient departments. However, data about their influence on human semen parameters, such as sperm concentration and motility, are contradictory. Therefore, the purpose of this study was to examine sperm function (acrosin activity and induction of the acrosome reaction) in smokers (n = 30) and varicocele patients (n = 30) compared with normal fertile donors (n = 20). The acrosome reaction was detected by triple staining after 3 h of incubation at 37 degrees C, followed by treatment with 0.1% dimethylsulphoxide (spontaneous acrosome reaction) and 10 microM calcium ionophore A23187 (induced acrosome reaction) for 1 h at 37 degrees C. Acrosin activity was measured by gelatinolysis. The diameters around the sperm heads after gelatinolysis and the percentages of spermatozoa showing halo formations were evaluated. The inducibility of the acrosome reaction was significantly lower in semen samples from smokers than in those from the fertile group (7.1 +/- 3.2 versus 11.2 +/- 4.0%, P < 0.01), whereas no statistically significant difference was demonstrated in spermatozoa from patients with varicocele (9.3 +/- 4.3%). Both the percentages of spermatozoa with halo formation (53.3 +/- 20.0 versus 76.6 +/- 13.6%, P < 0.05) and the halo diameters (16.1 +/- 6.6 versus 31.0 +/- 14.5 microns, P < 0.001) were significantly lower in the varicocele group than in the samples from fertile men. These data suggest that smoking and varicocele affect sperm function, and that the standard semen parameters alone are insufficient to evaluate the influence of both factors on human male fertility.