Infertility treatment for patients having a microdeletion of azoospermic factor (AZF).

In genetic causes of male infertility, Y chromosome microdeletions are the second most common after Klinefelter's syndrome. Although sperm recovery rate is relatively high for subjects with azoospermic factor (AZF) c chromosome microdeletion, intracytoplasmic sperm injection (ICSI) results using retrieved sperm has been reported to be poor. We retrospectively examined the infertility treatment for subjects with AZF microdeletion. From October 2017 to September 2020, chromosomal examination of 67 azoospermic subjects and 12 cryptozoospermia were performed. Of these, twenty-three subjects (29.1%) had AZF microdeletion. Twelve subjects with AZFc microdeletion and one subtype with unknown classification (Ym-9; P3 deletion) received sperm retrieval surgery due to azoospermia. Two subjects obtained motile sperm by microscopic epididymal sperm aspiration (MESA) and four subjects by microscopic testicular sperm extraction (micro-TESE). Pregnancy and healthy delivery were achieved in 6 of 14 subject (42.9%; including one twin) using ICSI. This was comparable with previous reports. Since there were two cases of obstructive azoospermia, we employed MESA to avoid testicular damage. Following observation of the testis and epididymis under operative microscope, a decision was made to perform sperm retrieval surgery to avoid unnecessary testicular damage. Furthermore, since AZFc microdeletion is passed to the next generation, long term follow-up is necessary.

Microscopic Epididymal Sperm Aspiration (MESA) Should be Employed Over Testicular Sperm Extraction (TESE) Sperm Retrieval Surgery for Obstructive Azoospermia (OA).

INTRODUCTION:  Testicular sperm extraction (TESE) has been widely used as a sperm extraction surgery for azoospermia even for obstructive azoospermia (OA) because it does not require surgical skill. However, there are postoperative pain issues, and subsequent testicular atrophy and decreased testosterone levels may occur with TESE. This study examines the usefulness of microscopic epididymal sperm aspiration (MESA) for OA. METHODS:  We studied 108 patients diagnosed with OA and treated with MESA at our institute between April 2004 and December 2021. The MESA was performed using a micropipette with a micropuncture technique under an operative microscope. When no sperm were present or motility was not observed, additional punctures to the epididymal tubule were performed. RESULTS:  Motile sperm were recovered in all cases (108 cases). Of these, intracytoplasmic sperm injection (ICSI) using frozen-thawed sperm was performed in 101 cases and the normal fertilization rate was 76.2%. A total of 436 embryo transfer (ET) cycles were performed. The implantation rate per transfer cycle was 47.9%, the clinical pregnancy rate was 41.0%, and the live birth rate was 23.7%. The per-case live birth rate was 84.8%. CONCLUSIONS:  MESA-ICSI has a very good fertilization rate, clinical pregnancy rate, and delivery rate. Furthermore, the patient's postoperative pain is less, the number of sperm collected is larger, the burden on the embryologist who processes the collected sperm is less, and ICSI can be easily attempted after frozen-thawed sperm. MESA rather than TESE should be employed for the OA subjects.

A Case of Suspected Isolated Follicle-Stimulating Hormone (FSH) Deficiency Where Spermatogenesis Was Acquired by Human Menopausal Gonadotropin (hMG).

Isolated follicle-stimulating hormone (FSH) deficiency is a rare cause of infertility in both sexes, and only a few cases have been reported in Japan. This is a case report of a young male patient with isolated FSH deficiency and azoospermia who was successfully treated with human menopausal gonadotropin (hMG). A 28-year-old male patient was referred for azoospermia. The delivery at his birth was uneventful and a family history of infertility or hypogonadism was not observed. The testes volume was 22/24 mL (right/left). No varicocele was observed in the ultrasound, and no sign or symptom of hypogonadism was found. In the semen analysis, however, the sperm concentration was as low as 2.5×106/mL and the motility was less than 1%. The endocrine panel revealed luteinizing hormone (LH) (2.1 mUI/mL, normal values 0.8-5.7 mUI/mL) and testosterone (6.57 ng/ml, normal values 1.42-9.23 ng/mL) were normal, while the FSH level was very low (0.6 mUI/mL, normal values 2.0-8.3 mIU/mL). The odor and the karyotype 46, XY, were normal. The brain MRI scans showed no abnormal findings. Genitalia and potency were normal. The diagnosis was made of isolated FSH with severe oligoastenozoospermia clinically.  FSH replacement therapy was employed. The patient self-injected 150 units of hMG three times a week. After 3 months of the treatment, the sperm concentration and motility went up to 264×106/mL and 12%, respectively. At 5 months, the patient's spouse conceived naturally, and at 7 months the treatment was terminated. During the treatment, FSH rose to the normal range, while other test items showed no change. The patient's health condition was uneventful. The spouse delivered a healthy boy. In conclusion, for isolated FSH with severe oligoastenozoospermia, hMG can be as effective as recombinant human FSH (rh-FSH), although the dosage remains a matter of discussion.

Evaluation of the serum zinc concentration in male infertility patients: an analysis of 2010 cases.

Zinc is an important trace element, and its importance for male infertility has been reported. The aim of the study was to assess whether the serum zinc concentrations were related to semen quality in male infertility patients. In 2010 subjects who consulted at our male infertility clinic between November 2018 and May 2021, serum zinc concentrations were assessed along with age, sperm concentration, sperm motility, endocrine panel, and body mass index (BMI). A normal zinc concentration was observed in 1069 (53.2%), subclinical deficiency in 845 (42.0%), and deficiency in 79 subjects (3.9%). On the other hand, high a zinc level was observed in only 17 subjects (0.9%). The serum zinc concentration did not relate with age, sperm concentration, sperm motility, luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone, and body mass index (BMI). However, normozoospermic subjects showed significantly higher zinc concentrations than among azoospermic (included non-obstructive; NOA and obstructive; OA) and cryptozoospermic patients. Furthermore, the zinc concentration was lower in NOA subjects when comparing to oligozoospermia and/or asthenozoospermia. An association between zinc concentration and semen analysis remained unclear. This study was cross-sectional and retrospective, however, this is a largest investigation of the zinc concentration during reproductive life span in Japan. Further accumulation of cases are required to further examine the potential relationship between zinc concentration and semen quality.

Secondary male infertility: the importance of the urological assessment for couples who desire children in later life.

Amongst 942 out-patients who consulted our male infertility division between 2016 to 2020, 85 (9.0%) patients suffered from secondary infertility. Of these, in 59 (69.4%) subjects, the first pregnancy was achieved by natural conception. 81 subjects were evaluated for semen quality except for two subjects who at the time were undergoing cancer treatment and another of two ejaculatory dysfunction (EjD). Semen analysis revealed 16 subjects (19.8%) were azoospermic, whereas 9 (11.1%) were cryptozoospermic at median three years of infertility. Left varicocelectomy had been undertaken in a total of 17 oligoasthenozoospermic and cryptozoospermic cases in order to improve semen quality. For achieving natural pregnancy, microscopic vasoepididymostomy was performed in 3 subjects of obstructive azoospemia and patency was achieved in two of three. 11 azoospermic subjects and two of the EjD underwent sperm retrieval surgery for intracytoplasmic sperm injection (ICSI). Motile sperm recovery was obtained by microscopic epididymal sperm aspiration (5/5=100%), microscopic testicular sperm extraction (micro-TESE, 2/6=33.3%), and retrograde vasal sperm aspiration (2/2=100%). Natural pregnancy was obtained in two subjects following varicocelectomy, and in one following vasoepididymostomy. Seven pregnancies were achieved by ICSI using cryopreserved sperm and surgically retrieved sperm. Even if the first pregnancy occurred naturally, 30.9% subjects showed azoospermia or cryptozoospermia at median duration of three years. We would like to emphasize that earlier urological assessment especially semen analysis is necessary if pregnancy later in life is desired.

A case of abdominal migration of the testes presenting with azoospermia.

31-year-old male was referred to our hospital due to azoospermia. Physical examination revealed impalpable testes in the scrotum, and operative scar presented at lower abdominal midline. Magnetic resonance imaging (MRI) revealed that small testes were located subcutaneously in the lower abdominal midline. Since luteinizing hormone (LH) and follicle stimulating hormone (FSH) were elevated, we diagnosed non-obstructive azoospermia (NOA) due to abdominal migration of the testes. Microscopic testicular sperm extraction (micro-TESE) was performed, however, no sperm were recovered. Pathological diagnosis was Sertoli cell only and no malignant cells were observed. Post-operatively, subjects' hormone levels were unchanged, and testicular tumor markers and computed tomography (CT) were normal. However, renal function gradually deteriorated and a renal transplantation from the farther was carried out eight months after micro-TESE. Attention to the possibility of carcinogenesis of the abdominal migrated testes should be maintained.

Male infertility treatment for cancer survivors: does anticancer treatment affect infertility treatment?

We investigated the impact of prior anticancer treatments such as chemotherapy and radiotherapy on subsequent infertility treatment in cancer survivors who consulted our male infertility division. Of 1,525 male infertility patients who consulted our division between 2008 and 2018, 56 (3.7%) were cancer survivors. Of these, 32 received anticancer treatment (group A) and 24 were treated with surgery alone or were seen before anticancer treatment (group B). Semen analysis revealed that azoospermia in 26 subjects (81.3%) and 14 (58.3%) in groups A and B respectively. Ejaculatory dysfunction was observed 1 in group A and in 2 group B subjects. Sperm cryopreservation before anticancer treatment was performed 4 subjects. Sperm retrieval surgery for intracytoplasmic sperm injection (ICSI) was performed in 13 cases in group A and 10 in group B. Motile sperm were recovered in 7 subjects and in 8 subjects in group A and B respectively. Overall pregnancies and deliveries with ICSI were achieved for 7 subjects (21.9%) in group A, and 9 (37.5%) in group B. Successful sperm retrieval may not be affected by prior anticancer treatment as shown in this study. However, some patients abandoned infertility treatment due to the cost of testing and sperm retrieval surgery. Support for the cost of infertility treatment in cancer survivors is necessary.

Microsurgical seminal reconstruction; our experiences in a single institute.

We assessed the contribution of microsurgical seminal reconstruction to achieving natural conception in conjunction with advanced assisted reproductive technologies. Ninety obstructive azoospermic subjects who underwent microsurgical seminal reconstruction were evaluated. Vasovasostomy (VV) was undertaken in 45 subjects whereas vasoepididymostomy (VE) in 45, respectively. VV was performed by employing a two microlayer anastomotic technique, whilst VE was undertaken using double needle longitudinal vaspepididymostomy (LIVE). Patency was achieved in 41 VV (91.1%), and 25 VE (55.6%) cases. In cases where patency was achieved, pregnancy and healthy delivery were recorded following natural intercourse in 7/41 (17.0%) VV, and in 7/25 (28.0%) VE cases. Where patency was not achieved, the use of cryopreserved sperm for intracytoplasmic sperm injection (ICSI), resulted in a healthy delivery in 4/4 (100%) VV and 14/21 (66.6%) in VE subjects. Although natural pregnancy was achieved only in a limited number of subjects treated (14/90; 15.6%), sperm harvested during surgery and cryopreserved for future ICSI use proved valuable, doubling the overall delivery rate (32/90; 36.6%). Surgical intervention is considered to be a useful technique in order to allow the possibility of a natural conception and by harvesting sperm at the same time contributes to the cost-effectiveness.

Clinical outcomes of microdissection testicular sperm extraction and intracytoplasmic sperm injection in Japanese men with Y chromosome microdeletions.

PURPOSE: We investigated the clinical results of Japanese men with Y chromosome microdeletions. METHODS: This study retrospectively examined 2163 azoospermic or severe oligozoospermic patients. We investigated the frequency of azoospermia factor (AZF) deletions and sperm retrieval rate (SRR) by microTESE in patients with these deletions, then analyzed the ICSI outcomes. RESULTS: Azoospermia factor deletions were found in 201 patients. SRR was significantly higher than that of the control group (74.0% vs 20.4%, P < .001). Thirty-three couples underwent ICSI using testicular spermatozoa retrieved by microTESE, and eight couples underwent ICSI using ejaculatory spermatozoa. The fertilization rate and clinical pregnancy rate per embryo transfer cycle were significantly higher in the ejaculatory group than that of the testicular group (66.4% vs 43.7%, P < .001, 53.3% vs 24.7%, P = .03, respectively). When compared with the control group, the fertilization rate was significantly lower in the testicular group with AZFc microdeletions (43.7% vs 53.6%, P < .001). CONCLUSIONS: Our study highlights that although microTESE in azoospermic men with AZFc microdeletions led to a higher SRR, ICSI outcomes of these men were worse than that of men without AZF deletions, even if testicular spermatozoa were retrieved.

Chronological changes in epidemiological characteristics of lower urinary tract urolithiasis in Japan.

OBJECTIVES: To determine changes and trends in the annual incidence and epidemiological aspects of lower urinary tract stones in Japan. METHODS: Data about patients who had been diagnosed by urologists in 2015 with first and recurrent lower urinary tract stones were collected from 301 hospitals approved by the Japanese Board of Urology. The estimated annual incidence according to sex, age and stone composition was compared with previous nationwide surveys between 1965 and 2005. RESULTS: The incidence of lower urinary tract stones in Japan has steadily increased from 4.7 per 100 000 in 1965 to 12.0 per 100 000 in 2015. However, the age standardized annual incidence of lower urinary tract stones has remained relatively stable over the same period at 5.5 per 100 000 and 6.0 per 100 000 in 1965 and 2015, respectively. The increase in incidence was most evident among individuals aged ≥80 years. The incidence of calcium oxalate stones has steadily increased among males and females, whereas that of infection-related stones has significantly decreased from 26.2% to 14.3% among men over the past 50 years. CONCLUSIONS: Nationwide surveys suggest a steady increase in the incidence of lower urinary tract stones over a 50-year period in Japan. This trend might reflect changes in the aging population and improved Japanese medical standards.

Chronological changes in the epidemiological characteristics of upper urinary tract urolithiasis in Japan.

OBJECTIVES: To assess epidemiological and chronological trends of upper urinary tract stones in Japan in 2015. METHODS: Patients with a first episode of upper urinary tract stones in 2015 were enrolled in this nationwide survey. The study included all hospitals approved by the Japanese Board of Urology, therefore covering most of the hospitals where urologists practice in Japan. The annual incidence and composition of urolithiasis were evaluated by age and sex. These results were compared with the previous results of the nationwide surveys from 1965 to 2005 to analyze temporal trends. RESULTS: The estimated annual incidence of a first-episode upper urinary tract stone in 2015 was 137.9 (191.9 in men and 86.9 in women) per 100 000. The estimated age-standardized first-episode upper urinary tract stone incidence in 2015 was 107.8 (150.6 in men and 63.3 in women) per 100 000, which did not represent a significant increase since 2005. An equivalent incidence was observed in patients aged >50 years, whereas a reduced incidence was observed in patients aged <50 years in both sexes. The proportion of patients who received percutaneous nephrolithotomy and/or ureteroscopy increased by approximately fivefold in the past 10 years. CONCLUSIONS: The steady increase in the annual incidence of upper urinary tract stones since 1955 leveled off in 2015. The current results show novel trends in the incidence and treatment modalities in the nationwide surveys of urolithiasis in Japan.

Superior clinical pregnancy rates after microsurgical epididymal sperm aspiration.

Purpose: To assess normal fertilization, clinical pregnancy, and live birth rates after the use of microscopic epididymal sperm aspiration (MESA). Methods: One-hundred-and-sixty azoospermic participants who underwent MESA were evaluated. The MESA was performed by using a micropuncture method with a micropipette. In cases in which motile sperm were not obtained after the MESA, conventional or micro-testicular sperm extraction (TESE) was completed. Results: Adequate motile sperm were retrieved in 71 participants by using MESA and in 59 out of 89 participants by using TESE. Of the total number of patients, 123 underwent intracytoplasmic sperm injection. After MESA, the normal fertilization rate was 73.5% and the clinical pregnancy rate per case was 95.7%. Healthy deliveries resulted after MESA in 65 (92.9%) cases and after TESE in 38 (71.7%) cases. Conclusion: The MESA specimen collection does not have any special requirements, such as mincing tissue disposition. The MESA also can reduce the amount of laboratory work that is needed for cryopreservation. In the authors' experience, MESA is a beneficial procedure and should be given priority over TESE.

Leydig cell tumor of the testis, presenting with azoospermia.

Case: A case of Leydig cell tumor, associated with azoospermia, is presented. Outcome: The levels of sex hormones obviously were decreased, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH), with elevated testosterone. Computed tomography revealed no adrenal gland tumor, but a significant calcification in the right scrotal content was observed. He received a right radical orchiectomy and then he was unable to ejaculate. An endocrine panel revealed significantly decreased levels of testosterone and the low LH level had remained. Hormone replacement therapy with combined LH and FSH successfully recovered and preserved spermatogenesis. Conclusions: Although the patient's sexual function deteriorated after surgery, hormone replacement therapy was successful in establishing spermatogenesis.

Contemporary outcomes of seminal tract re-anastomoses for obstructive azoospermia: a nationwide Japanese survey.

OBJECTIVES: To evaluate current outcomes of seminal tract re-anastomoses in Japan, and to compare them with historical data. METHODS: A total of 213 patients with obstructive azoospermia who underwent seminal tract re-anastomosis from April 2008 to March 2012 at 25 institutions were enrolled in the present study. The outcomes of the procedure were compared with those reported in a previous multi-institutional study carried out in 2000. RESULTS: The percentage of partners aged over 35 years was 37%. A microsurgical double-layer anastomosis was carried out 83.0% of the time. Sperm were observed in ejaculate postoperatively in 68.9% and 41.5% of patients who underwent a vasovasostomy or a vasoepididymostomy, respectively. Natural conception occurred in 27.5% of patients after a vasectomy and 32.3% of patients with an epididymal obstruction. Except for the ratio of natural conception in patients with vasal obstruction after herniorrhaphies, there were no significant differences in final ratios of sperm appearance and natural conception between the previously reported study and the present study. CONCLUSIONS: Compared with historical data, contemporary seminal tract re-anastomosis in Japan seems to provide equivalent or better outcomes, depending on the cause of obstruction. Seminal tract re-anastomosis is a valid treatment option for patients with obstructive azoospermia.

DPP-IV inhibitor may affect spermatogenesis.

A 39-year-old physician was diagnosed retrograde ejaculation due to diabetes and treated with amoxapine. This treatment was effective; he could ejaculate. He began receiving DPP-IV inhibitor (Sitagliptin 50 mg, daily), in lieu of insulin injection. Unusual effect on semen quality was occurred following the administration of the drug.

Potential of molecular targeted therapy of HER-2 and Cox-2 for invasive transitional cell carcinoma of the urinary bladder.

Expression of HER-2 and COX-2 was determined to assess the potential of molecular-targeted therapy against human epidermal growth factor receptor-2 (HER-2) and cyclooxygenase-2 (COX-2) for the treatment of invasive bladder cancer. The subjects were 46 patients who attended Aichi Medical University Hospital between January 2001 and August 2008, underwent total cystectomy with a diagnosis of M0 bladder cancer, and received a pathological diagnosis of invasive transitional cell carcinoma of the urinary bladder (pT2-pT4). Expression of HER-2 and COX-2 was determined by immunohistochemical staining, and the results were interpreted by two pathologists by classifying HER-2 expression into four grades, and considering COX-2 positive when 10% or more of the tumor cells were stained. In HER-2 immunostaining, 10 subjects (21.7%) were positive, all of whom had a Grade 3 tumor. Staging classification identified 2 subjects (2/22, 9.1%) with pT2 stage, 3 (3/16, 18.8%) pT3 stage, and 5 (5/8, 62.5%) pT4 stage. There was a correlation between HER-2 positivity and tumor stage (P=0.007). Lymph node metastasis was detected in 13 subjects, 3 of them (3/8, 37.5%) with pN2 metastasis were HER-2 positive. The 5-year cause-specific survival rate was 51.4% for HER-2-positive subjects and 83.4% for HER-2-negative subjects. The outcome was poorer in HER-2-positive subjects, but the difference in survival rate was not statistically significant (P=0.218). In COX-2 immunostaining, 27 subjects (58.7%) were found to be positive. Three (3/4, 75.0%) showed a Grade 2 tumor and 24 (24/42, 57.1%) a Grade 3 tumor. Staging classification identified 13 subjects (13/22, 59.1%) with pT2 stage, 9 (9/16, 56.3%) pT3 stage, and 5 (5/8, 62.5%) pT4 stage. There was no correlation between COX-2 positivity and tumor grade or stage (P=0.488 and 0.089, respectively). Classification by the extent of lymph node metastasis revealed that 6 subjects (6/8, 75.0%) with pN2 were COX-2 positive. There was a correlation between COX-2 positivity and the extent (pN1 or pN2) of lymph node metastasis (P=0.008). The 5-year cause-specific survival rate was 84.0% for COX-2-positive subjects and 71.7% for COX-2-negative subjects. However, the difference in survival rate was not significant (P=0.407). Seven subjects (7/46, 15.2%) were positive for both HER-2 and COX-2, and there was no statistically significant correlation between the status of HER-2 expression and that of COX-2 expression (P=0.2195). The present study failed to show any association between HER-2 or COX-2 positivity and outcome in subjects with invasive bladder cancer. However, HER-2-positive subjects tended to have a poorer outcome. This finding suggests that molecular-targeted therapy against HER-2 could be an effective therapy. Further studies involving a larger number of subjects are required.

Penetration of doripenem into prostatic tissue following intravenous administration in prostatectomy patients.

This study examined the prostatic penetration of doripenem in prostatectomy patients. Doripenem 500 mg was administered by a 0.5-h infusion and venous blood and prostatic tissue samples were obtained up to 5h afterwards. Drug concentrations in plasma and prostatic tissue were measured chromatographically. The observed maximum concentration (C(max)) (mean+/-standard deviation; n=9) was 27.5+/-5.1 microg/mL in plasma and 5.09+/-1.94 microg/g in prostate tissue and the prostate/plasma C(max) ratio was 0.189+/-0.078. The area under the drug concentration-time curve (AUC) was 49.7+/-6.9 microg h/mL in plasma and 3.93+/-1.89 microg h/g in prostate tissue and the prostate/plasma AUC ratio was 0.081+/-0.047. Based on a three-compartment pharmacokinetic analysis, average drug exposure times above 0.25 microg/mL (the minimum inhibitory concentration for isolates of common pathogens) in the prostate were 23.2% for 500 mg once daily, 46.2% for 500 mg twice daily and 69.9% for 500 mg three times daily. The 500-mg regimens all achieved the drug exposure time target (bacteriostatic 20% or bactericidal 40%) in the prostate, despite the relatively low penetrability of doripenem.

Retrograde vasal sperm aspiration in anejaculatory patients with spinal cord injury.

Aim: This paper describes our experience with retrograde vasal sperm aspiration (ReVSA) in anejaculatory patients with spinal cord injury. Methods: We performed 11 vasal sperm aspiration procedures on eight patients presenting with neurogenic anejaculation associated with spinal cord injury at our institute between 2004 and 2007. This procedure was conducted under local anesthesia with a spermatic block. A 24G needle was inserted into the vas in a retrograde fashion. Sperm-washing medium was gently injected into the proximal vas several times and collected. Aspirated sperm was cryopreserved for intracytoplasmic sperm injection. Results: Adequate motile sperm was obtained from all patients. All couples underwent intracytoplasmic sperm injection; clinical pregnancies were achieved in eight cases (two ongoing pregnancies and the births of six healthy babies). Conclusion: Retrograde vasal sperm aspiration is a reliable method for the consistent recovery of sperm of sufficient quality to afford a high pregnancy rate and in sufficient quantity to permit cryopreservation of excess sperm for future use. (Reprod Med Biol 2008; 7: 115-118).

8-Hydroxydeoxyguanosine levels in human leukocyte and urine according to exposure to organophosphorus pesticides and paraoxonase 1 genotype.

OBJECTIVE: In order to investigate a role of paraoxonase 1 (PON1) polymorphism in organophosphorus (OP)-induced 8-hydroxydeoxyguanosine (8-OHdG) levels, urinary metabolites of OP, PON1 genotypes, and 8-OHdG levels in leukocyte and urine were measured in OP indoor insecticide sprayers and controls in summer and winter. METHODS: The study population contained 18 male sprayers and age-matched 18 male controls. Sprayers were primarily exposed to OP insecticides (mainly fenitrothion, dichlorvos, chlorpyrifos, and diazinon), and partially to pyrethroids (mainly permethrin) and carbamates (mainly propoxur). Urinary metabolites of OP were measured by gas chromatography-mass spectrometry. 8-OHdG levels in leukocyte and urine were measured by ELISA kit. PON1 genotype was identified using allele-specific fluorogenic TaqMan probes. RESULTS: The mean concentrations of urinary dimethyl phosphate (DMP) and total dialkyl phosphates (DAP) in summer and those of 8-OHdG in summer and winter were significantly higher in OP sprayers than controls. This resulted in a significant positive correlation between 8-OHdG levels and urinary DMP or DAP, suggesting a correlation between OP metabolites and production of oxidative stress. Of PON1 genotypes, incidences of Q/Q, Q/R, and R/R types were 17, 39, and 44% in OP sprayers and controls, respectively. Although PON1 polymorphism did not contribute to the leukocyte and urinary 8-OHdG levels, the urinary OP metabolite concentrations in summer showed a significant decrease as the number Q allele decreased. CONCLUSION: These results indicate that an increase in OP metabolites is associated with a high level of oxidative stress in OP sprayers, although the contribution of the PON1 polymorphism to the metabolism of OP is still unclear.