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C Foresta

Publications and source records attributed to C Foresta.

At least 73 records · Page 4Linked to original sources
PubMed1999

Inhibin B plasma concentrations in oligozoospermic subjects before and after therapy with follicle stimulating hormone.

The aim of this study was to investigate inhibin B and follicle stimulating hormone (FSH) secretion in a large group of oligozoospermic subjects affected by different degrees of testicular damage, before and after FSH treatment. A total of 135 oligozoospermic subjects (sperm count < 20 x 10(6)/ml) were evaluated for seminal parameters and FSH, luteinizing hormone (LH), testosterone and inhibin B plasma concentrations. Testicular structure was analysed with bilateral fine needle aspiration cytology. Inhibin B showed an inverse correlation with FSH, no correlation with sperm concentration and a significant relationship with intratesticular spermatid number, demonstrating that testicular spermatids play an important role in the control of inhibin B production. Twenty-five subjects with sperm counts < 10 x 10(6)/ml were treated with FSH; 11 of these had basal FSH and inhibin B plasma concentrations in the normal range (group A), while in seven subjects FSH was elevated (> 7 IU/l) with normal inhibin B (group B), and in seven patients FSH was high and inhibin B reduced (< 80 pg/ml) (group C). During treatment, in group A patients inhibin B plasma concentrations increased significantly after 2, 3 and 4 weeks of FSH administration and declined thereafter to pre-treatment concentrations. Groups B and C did not show any modification during the treatment. In the same period, in group A FSH increased significantly after 2, 3 and 4 weeks and subsequently declined. In groups B and C, FSH increased significantly after 2 weeks and remained elevated during the following period. The results of the present study confirm the significant inverse correlation between inhibin B and FSH plasma concentrations in subjects with disturbed spermatogenesis, and demonstrate that inhibin B reflects Sertoli cell function and their interaction with spermatids. FSH and inhibin B concentrations are an expression of the spermatogenic status of seminiferous tubules. FSH treatment seems to modify inhibin B plasma concentrations only in subjects with normal basal FSH and inhibin B, independently from the effects of this therapy on sperm production.

Adult↗
PubMed1999

Human male infertility and Y chromosome deletions: role of the AZF-candidate genes DAZ, RBM and DFFRY.

Microdeletions in Yq11 overlapping three distinct 'azoospermia factors' (AZFa-c) represent the aetiological factor of 10-15% of idiopathic azoospermia and severe oligozoospermia, with higher prevalence in more severe testiculopathies, such as Sertoli cell-only syndrome. Using a PCR-based screening, we analysed Yq microdeletions in 180 infertile patients affected by idiopathic Sertoli cell-only syndrome and different degrees of hypospermatogenesis, compared with 50 patients with known causes of testicular alteration, 30 with obstructive azoospermia, and 100 normal fertile men. In idiopathic severe testiculopathies (Sertoli cell-only syndrome and severe hypospermatogenesis), a high prevalence of microdeletions (34.5% and 24.7% respectively) was found, while milder forms were not associated with Yq alteration. No deletions were found in testiculopathies of known aetiology, obstructive azoospermia, normal fertile men and male relatives of patients with deletions. Deletions in the AZFc region involving the DAZ gene were the most frequent finding and they were more often observed in severe hypospermatogenesis than in Sertoli cell-only syndrome, suggesting that deletions of this region are not sufficient to cause complete loss of the spermatogenic line. Deletions in AZFb involving the RBM gene were less frequently detected and there was no correlation with testicular phenotype, with an apparent minor role for such gene in spermatogenesis. The DFFRY gene was absent in a fraction of patients, making it a candidate AZFa gene. Our data suggest that larger deletions involving more than one AZF-candidate gene are associated with a more severe testicular phenotype.

Chromosome Deletion↗
PubMed1999

Absence of testicular DAZ gene expression in idiopathic severe testiculopathies.

Deletions of the DAZ (deleted in azoospermia) gene family are frequently responsible for male infertility and are generally assessed by analyses of genomic DNA extracted from peripheral leukocytes. The multicopy nature of this gene prevents the distinction of intragenic deletions or deletions not involving the whole DAZ gene cluster. Thus it is still unclear whether each DAZ copy is effectively expressed in the testis. We analysed, by reverse transcription-polymerase chain reaction (RT-PCR), the expression of DAZ, RBM and SRY genes, in testicular cells from infertile men affected by idiopathic severe hypospermatogenesis, obstructive azoospermia and Sertoli cell-only syndrome. Normal mRNA for DAZ, RBM and SRY were observed in obstructive azoospermia, whereas only SRY transcripts were detected when only Sertoli cells were present. Nine out of 10 patients affected by idiopathic severe hypospermatogenesis had normal expression of SRY, RBM and DAZ, while in one patient no DAZ transcript was detected, suggesting that his testiculopathy was related to the absence of DAZ expression. The lack of DAZ mRNA in testicular cells with an apparently normal DAZ gene constitution on DNA extracted from leukocytes may be explained by different hypotheses: (i) not all the copies of the DAZ gene cluster are transcribed in the germ cells and the reported patient had a small deletion involving only the active ones; (ii) the patient may be mosaic for the DAZ gene having a normal constitution in leukocytes and be deleted for DAZ gene in the testis; (iii) abnormalities of DAZ transcription may exist. These findings highlight the intrinsic interpretative difficulties of normal PCR analysis for DAZ and RBM on leukocytes and suggest caution in the use of germ cells for assisted reproductive techniques in these cases to avoid transmission of genetic abnormalities to male offspring.

Biopsy, Needle↗
PubMed1999

Analysis of meiosis in intratesticular germ cells from subjects affected by classic Klinefelter's syndrome.

Azoospermic subjects affected by Klinefelter's syndrome may occasionally show the presence of intratesticular residual foci of spermatogenesis, and the retrieval of mature spermatozoa from the testis may permit fertility and paternity by means of intracytoplasmic sperm injection. Previous studies have demonstrated that these subjects show the presence of an increased incidence of hyperaploid spermatozoa. Here we analyzed, by fluorescence in situ hybridization using specific probes for chromosomes 8, X, and Y, the spermatogenic process and the meiotic progression of 47,XXY germ cells retrieved by fine needle aspiration of the testis in ten azoospermic patients affected by classic Klinefelter's syndrome. All patients had lower testicular volume, higher gonadotropins, and lower testosterone plasma levels compared with control subjects. Cytological analysis of the testicular cells retrieved by fine needle aspiration showed the presence of Sertoli cells only in eight subjects, while germ cells were observed in two patients. In each patient Sertoli cells showed a 47,XXY karyotype, and the same chromosome pattern was observed in spermatogonia and primary spermatocytes of patients presenting a residual spermatogenesis. Secondary spermatocytes, spermatids, and mature spermatozoa showed different sex chromosome patterns, reflecting their origin from 47,XXY spermatogonia. In conclusion, this study demonstrated that, in subjects affected by Klinefelter's syndrome, residual germ cells may be present in the testis and that 47,XXY spermatogonia are able to undergo and complete the spermatogenic process leading to mature spermatozoa. These data further suggest the need to evaluate the sex chromosome status of sperm from patients affected by Klinefelter's syndrome undergoing assisted reproductive techniques.

Adult↗
PubMed1999

Y chromosome microdeletions in cryptorchidism and idiopathic infertility.

To clarify whether cryptorchidism might be the expression of an intrinsic congenital testicular abnormality, we investigated the frequency of Y chromosome long arm (Yq) microdeletions in unilateral excryptorchid subjects manifesting an important bilateral testiculopathy. Microdeletion analysis of Yq was performed by polymerase chain reaction in the following subjects: 40 unilateral excryptorchid patients with azoospermia or severe oligozoospermia due to a bilateral severe testiculopathy (Sertoli cell-only syndrome or severe hypospermatogenesis); 20 unilateral excryptorchid men with moderate oligozoospermia and a normal testicular cytological picture in the contralateral testis; 110 patients affected by idiopathic severe primary testiculopathies; 20 patients affected by idiopathic moderate testiculopathy; and, as controls, 50 patients affected by known causes of testiculopathy and 100 fertile men. Eleven of 40 (27.5%) unilateral excryptorchid patients affected by bilateral testiculopathy and 28 of 110 (25.4%) patients affected by idiopathic severe primary testiculopathy showed Yq microdeletions, whereas no microdeletions were found in all the other subjects, nor in male relatives of patients with deletions. Microdeletions were located in different parts of Yq, including known regions involved in spermatogenesis (DAZ and RBM, AZFa, b, and c) and other loci still poorly defined. No difference in localization of deletions was evident between cryptorchid and idiopathic patients. Microdeletions in Yq may be responsible for severe bilateral testicular damage that could be phenotypically expressed by unilateral cryptorchidism, as well as by idiopathic infertility.

Adult↗
PubMed1998

Evidence for a stimulatory role of follicle-stimulating hormone on the spermatogonial population in adult males.

OBJECTIVE: To evaluate the effects of treatment with FSH on seminal indices and on the seminiferous epithelium of oligozoospermic subjects with normal FSH plasma levels. DESIGN: Placebo-controlled, double-blind randomized study. SETTING: Academic setting. PATIENT(S): Ninety subjects with idiopathic oligozoospermia (sperm count of < 10 x 10(6)/mL) and normal plasma levels of FSH. INTERVENTION(S): Three months of treatment with FSH (60 patients) or placebo (30 patients); bilateral testicular fine-needle aspiration. MAIN OUTCOME MEASURE(S): Seminal indices; testicular cytologic features; plasma levels of FSH, LH, and testosterone; and ultrasonographic testicular examination. RESULT(S): According to seminal indices, patients treated with FSH and placebo were classified as nonresponders or as responders (as determined by at least a doubling of sperm count). No placebo-treated patients responded to treatment. Among FSH-treated patients, 20 responded to hormonal treatment and 40 did not. The results of pretreatment cytologic examination of testicular specimens from patients who did not respond to FSH treatment were consistent with hypospermatogenesis associated with maturational disturbances at the spermatid level. In contrast, patients who responded to treatment with FSH had isolated hypospermatogenesis without maturational disturbances. After FSH therapy, we detected an increase of spermatogonia and spermatocyte population in both the responder and nonresponder subjects. This increase was associated with an activation of spermatogenic and spermiogenic processes and with a rise in ejaculated sperm concentration only when isolated hypospermatogenesis was present (responder patients). CONCLUSION(S): The findings of this study demonstrate that FSH treatment increases the spermatogonial population in men. This treatment may be appropriate for oligozoospermic subjects who have normal FSH plasma levels and a testicular evaluation characterized by hypospermatogenesis without maturational disturbances.

Adult↗
PubMed1998

Doppler ultrasound of the testis in azoospermic subjects as a parameter of testicular function.

Azoospermia frequently represents the end-point of different pathological conditions that cause important quantitative and qualitative alterations of both spermatogenesis and testicular structure, including intratesticular blood vessels. In this study we performed colour Doppler ultrasound of the testis in 12 azoospermic subjects affected by primary testicular pathology (four bilateral post-orchitis, four postradiotheraphy for cancer, four post-traumatic) aged 28.2+/-3.3 (mean+/-SD) years, in six subjects affected by obstructive azoospermia aged 29.7+/-2.4 years and in 20 age-matched fertile subjects (aged 28.6+/-2.5 years). The analysis of intratesticular vessels per organ was quantified using a semiquantitative score: category 0, no vessels visible; category 1, between one and three intratesticular vessels visible; and category 2, more than three vessels visible. In obstructive azoospermic patients and in fertile subjects there were always more than three intratesticular vessels. No intratesticular vessels were detected in eight testes (33.3%) and fewer than three vessels in 16 testes (66.6%) in subjects affected by primary testicular pathology. In azoospermic subjects the testicular structure of the testis was evaluated by diagnostic fine needle aspiration cytology (FNAC) performed in the middle portion of the testis. In non-obstructive azoospermic patients this procedure showed the presence of only Sertoli cells in all cases. When detectable vessels were present, a new aspiration was performed in these areas. In 12 out of 16 cases, spermatogenetic cells including mature spermatozoa, were found when the FNAC was performed in testicular regions showing the presence of blood vessels. These results indicate that colour Doppler sonography of the testis may be useful in the differential diagnosis of azoospermia and suggest the evaluation of the intratesticular blood vessel distribution before performing any method to retrieve intratesticular spermatozoa for intracytoplasmic sperm injection.

Adult↗
PubMed1998

High frequency of well-defined Y-chromosome deletions in idiopathic Sertoli cell-only syndrome.

Idiopathic Sertoli cell-only syndrome (SCOS) is characterized by azoospermia, small testes, absence of germ cells in the testes, elevated follicle stimulating hormone and normal testosterone concentrations. The Y-chromosome is involved in the regulation of spermatogenesis and in the pathogenesis of a fraction of idiopathic male infertility. An azoospermia factor (AZF) is present on the Y-chromosome long arm euchromatic region (Yq11) and two gene families (DAZ and RBM) have been identified within this region. The aim of this study was to investigate whether a specific pattern of Yq11 microdeletions may be associated with idiopathic SCOS. Eighteen idiopathic subjects showing a testicular cytological picture of bilateral SCOS were selected and tested by polymerase chain reaction for a set of 29 Y-specific sequence-tagged sites (STS). We found Yq microdeletions in 10 out of 18 patients (55.5%) while the fathers or brothers of six out of 10 patients deleted for Yq were shown to carry an intact Y-chromosome. These deletions may therefore be considered as de-novo deletions and the cause of SCOS. The analysis of the microdeletions allowed us to identify two homogeneous regions that have a high incidence of deletion. The smallest deletion, common to all patients, is located in Yq interval 5. We therefore speculate that there is a relationship between specific, well-characterized Yq11 microdeletions and a testicular picture of SCOS, identifying an Y-related region frequently deleted in this syndrome. In conclusion, the findings of this study demonstrate that a large percentage of idiopathic SCOS may be genetically determined and identify an Y-related region that seems to possess one or more still unknown genes essential for spermatogenesis.

Chromosome Deletion↗
PubMed1998

Case report: high fertilization rate in conventional in-vitro fertilization utilizing spermatozoa from an oligozoospermic subject presenting microdeletions of the Y chromosome long arm.

A case is reported in which a high fertilization rate was achieved by conventional in-vitro fertilization (IVF), using spermatozoa from an oligozoospermic man carrying a microdeletion of the long arm of the Y chromosome. The patient presented with idiopathic infertility of 10 years duration; the fertility status of his wife was completely normal. After IVF, five out of eight oocytes retrieved showed normal fertilization and four showed normal embryo cleavage. Four embryos were transferred; however, pregnancy did not result. These results demonstrate that spermatozoa from oligozoospermic patients carrying a Yq microdeletion are fully competent in achieving capacitation, acrosome reaction and fertilizing ability during IVF. Therefore, although definitive conclusions cannot be made from a single case report, we suggest that Yq microdeletion analysis should be considered in oligozoospermic patients undergoing conventional IVF.

Adult↗
PubMed1998

High incidence of sperm sex chromosomes aneuploidies in two patients with Klinefelter's syndrome.

In this study we have investigated the arrangement of sex chromosomes in sperm from two severe oligozoospermic patients, apparently affected by the classic form of Klinefelter's syndrome (KS). Multicolor fluorescence in situ hybridization has been used to recognize chromosomes X, Y, and 8 in sperm from patients and 10 fertile men with normal 46,XY karyotype. In patients affected by KS, we detected important numerical sex chromosome abnormalities (approximately 20%). In all normal fertile men, X- and Y-bearing spermatozoa were present in a 1:1 ratio. On the contrary, in our patients the frequency of 23,Y-bearing sperm was strongly reduced compared with that of both 23,Y sperm in the controls and 23,X sperm in the same subject affected by KS, resulting in a 23,X-/23,Y-bearing sperm ratio of 2:1. Moreover, the frequency of 24,XY disomic sperm was significantly higher in the absence of the 22,0 hypoaploidy expected from a common origin from a nondysjunction during the first meiosis in a normal 46,XY cell. In conclusion, the results of the present study demonstrate a peculiar distribution of sex chromosomes in sperm from two patients with KS, in agreement with the hypothesis that 47,XXY germ cells are able to complete the meiotic process by producing mature spermatozoa.

Adult↗
PubMed1998

Influence of age and sex on serum concentrations of total dimeric activin A.

Several studies have shown that activin A is secreted in substantial amounts into the systemic circulation. The changes that occur during menstrual cycle and pregnancy suggest a correlation with reproductive function. At present, however, no definitive evidence has confirmed this pattern throughout adult life; moreover, neither the origin nor the physiological implications of this circulating growth factor have been clearly defined. The aim of the present study was to evaluate whether circulating concentrations of activin A change in adult men and women according to age and sex, and to examine the possible correlation with serum concentrations of FSH. Total dimeric activin A was measured using a specific two-site enzyme immunoassay in serum specimens collected from a cohort of normal individuals enrolled in an epidemiological survey. A group of men (n = 106) and one of women (n=151) were subdivided into six age groups (20-30, 30-40, 40-50, 50-60, 60-70 and 70-90 years). In a small group of 8 men and 11 women, serum concentrations of activin A were evaluated twice, in specimens collected at an interval of 10 years. Serum FSH concentrations were also measured in all specimens. Serum concentrations of activin A were not significantly different in men and women and showed an age-related progressive increase between 20 and 50 years of age (P<0.01, those aged 40-50 compared with those aged 20-30 years). After the age of 50 years, activin A concentrations remained in the same range of values in women, whereas they increased significantly in men, reaching peak values between 70 and 90 years (P<0.01 compared with the group aged between 20 and 50 years). From the age of 50 years, activin A concentrations were significantly greater in men compared with those in women in the corresponding age groups (P<0.001). Activin A concentrations correlated with age in men, but not in women. No significant correlation between concentrations of activin A and FSH was found in either sex. Activin A concentrations in specimens collected 10 years apart showed an increase in seven of eight men, but not in women. Finally, no significant variations of activin A concentrations were observed when fertile and postmenopausal women were compared. The present data indicate that circulating concentrations of activin A vary according to age; furthermore, men older than 50 years have greater concentrations than women. These changes, which occur irrespectively of FSH concentrations, indicate that circulating activin A is not a hormone of the reproductive axis.

Activins↗
PubMed1997

Pituitary adenylate cyclase activating polypeptide stimulates rat Leydig cell steroidogenesis through a novel transduction pathway.

The aim of the present study was to evaluate the effects of pituitary adenylate cyclase activating polypeptide (PACAP) on testosterone production in isolated adult rat Leydig cells and its possible mechanisms of action. PACAP-38 stimulated testosterone secretion in a dose-dependent manner with a minimal and a maximal efficacious dose of 1.0 nM and 100 nM, respectively. PACAP-27 was without effect on testosterone secretion at any dose tested. Similarly, vasoactive intestinal peptide did not stimulate steroidogenesis nor interfere with PACAP-38 activity, as well as preincubation of Leydig cells with the vasoactive intestinal peptide-antagonist [Lys(1), Pro(2,5), Arg(3,4), Tyr(6)]-vasoactive intestinal peptide. Removal of extracellular Ca2+ did not inhibit the stimulatory effects of PACAP-38 on Leydig cell testosterone production. Neither PACAP-38 nor PACAP-27 modified intracellular free Ca2+ and cAMP levels at any dose tested thus excluding a role for Ca2+ and cAMP in the stimulatory effects of PACAP. PACAP-38 was able to induce a plasma membrane depolarization that was dependent on an influx of Na+ from the extracellular medium as confirmed by the monitoring of intracellular Na+ with the Na+-sensitive fluorescent dye sodium benzofuran isophtalate. When Na+ was removed from the extracellular medium, PACAP-38 did not stimulate testosterone production, demonstrating that Na+ influx through the plasma membrane is strictly related to the stimulatory effects of this peptide. In addition, preincubation of Leydig cells in the presence of pertussis-toxin (500 ng/ml for 5 h) significantly reduced PACAP-38-stimulated effects both on plasma membrane depolarization and testosterone secretion. These results demonstrate that PACAP-38 stimulates testosterone secretion in isolated adult rat Leydig cells through the interaction with a novel PACAP receptor subtype coupled to a pertussis toxin sensitive G protein whose activation induces a Na+-dependent depolarization of the plasma membrane and testosterone production.

Adenylate Cyclase Toxin↗
PubMed1997

Y-chromosome deletions in idiopathic severe testiculopathies.

A genetic etiology has been recently proposed for some severe forms of idiopathic male infertility and a region of the Y chromosome long arm (Yq) defined AZF is thought to be critical for the regulation of spermatogenesis. To date, two genes, YRRM and DAZ, have been identified in AZF, but the actual relationship between genotype and phenotype related to AZF deletions is not well characterized. By means of a PCR strategy we typed Yq microdeletions in 16 azoospermic and 22 severely oligozoospermic subjects whose testicular cytological picture (assessed by fine needle aspiration) was that of Sertoli cell-only syndrome and severe hypospermatogenesis, respectively. Microdeletions in AZF were found in 37.5% of azoospermic men and in 22.7% of severely oligozoospermic men, suggesting that very frequently these genetic abnormalities determine a severe quantitative defect in spermatogenesis. Furthermore, DAZ and YRRM do not seem to be the sole genes regulating spermatogenesis, as deletions in these genes were observed in only 6 of the 11 deleted cases. No correlation between the spermatogenic defect and the type of Yq deletion exists. Intracytoplasmic sperm injection performed using spermatozoa of these Y-deleted patients will invariably pass this defect onto their male offspring. Screening for deletion within AZF or at least an informed consent should, therefore, be obtained in all idiopathic infertile male undergoing a program of intracytoplasmic sperm injection of a spermatozoon into the oocyte.

Adult↗
PubMed1997

Specific linkages among luteinizing hormone, follicle-stimulating hormone, and testosterone release in the peripheral blood and human spermatic vein: evidence for both positive (feed-forward) and negative (feedback) within-axis regulation.

We have investigated possible (negative) feedback and (positive) feed-forward activity within the human male gonadotropic axis by measuring serum concentrations of LH, FSH, and testosterone in blood sampled frequently and for a prolonged interval (every 20 min for 19 h) simultaneously from the peripheral circulation and the left spermatic vein. Cross-correlation analysis with time lag was used to evaluate relationships among serial serum LH, FSH, and/or testosterone concentrations over time (i.e. consistency or dissociation of trends in concentrations). Separately, Cluster analysis was applied to identify discrete LH, FSH, and testosterone pulses, which were cataloged for possible peak coincidence. The hypergeometric probability distribution was then used to test the null hypothesis that LH, FSH, and testosterone pulses are randomly associated. Cross-correlation analysis revealed: 1) peripheral blood LH and testosterone concentrations correlate positively at lags of 40-120 min with LH increases preceding testosterone increases, viz., feed-forward (P < 0.001); 2) LH and FSH concentrations in peripheral blood are positively correlated in simultaneous blood samples, as well as when FSH lags LH by 20 min (P < 0.01); 3) unexpectedly, LH and FSH concentrations in peripheral blood are inversely related at a lag of 80-100 min (P = 0.002) and 0.004, respectively) where LH lags FSH; 4) LH and testosterone concentrations in the spermatic vein show strongly positive correlations at lags of 80, 100, and 120 min (P = 0.002, 0.004, and 0.021, respectively); 5) spermatic vein testosterone concentrations correlate negatively with peripheral blood LH concentrations 20 or 40 min later (P = 0.012 and 0.05, respectively), which indicates autonegative feedback; and 6) in contrast, testosterone levels in the spermatic vein correlate negatively with FSH values in the periphery 100 and 120 min later (P < 0.01), indicating more delayed negative feedback of testosterone on serum FSH concentrations. Discrete pulse coincidence analysis disclosed: 1) a total of 30 testosterone pulses in the spermatic vein and 25 testosterone pulses in peripheral blood, with 28 LH and 29 FSH pulses in the periphery; 2) individual LH and FSH peak concordance was significantly nonrandom for FSH pulse maxima lagging LH pulse maxima by 20 min (P < 0.05 vs. randomness), with 6 observed coincidences vs. 2.9 +/- 1.5 (SD) expected; 3) peripheral LH pulses and spermatic vein testosterone pulses were strongly nonrandomly coupled at an 80-min lag, with 8 events observed vs. 3.0 +/- 1.5 events expected (P = 0.004); and 4) LH peaks in peripheral blood followed testosterone peaks in the spermatic vein by 40 min in a nonrandom manner, specifically, n = 11 observed vs. 3.0 +/- 1.5 expected (P < 0.001), indicating possible LH escape from testosterone's negative feedback. In summary, physiological regulation of the human male LH, FSH, and testosterone axis comprises multidirectional interactions, consisting of both (positive) feed-forward and (negative) feedback coupling. Based on a concept of network integration, we propose that age and other pathophysiological factors might modulate and/or disrupt these dynamic within-axis multihormonal linkages.

Adolescent↗
PubMed1996

Role of P2-purinergic receptors in rat Leydig cell steroidogenesis.

The present study investigated the effects of extracellular ATP on the intracellular calcium ion concentration ([Ca2+]i) and testosterone production in isolated adult rat Leydig cells. This nucleotide caused an increase in [Ca2+]i, with a maximal effect at a concentration of 100 microM ATP, comprising a rapid initial spike followed by a long-lasting plateau. The first rapid spike was dependent on the release of Ca2+ from internal stores, since it also occurred in Ca(2+)-free medium and was abolished after depletion of internal stores with thapsigargin. The second, long-lasting, phase was dependent on the influx of Ca2+ from the extracellular medium. After 3 h of incubation, extracellular ATP stimulated testosterone secretion in a dose-dependent manner, with a maximal effect at 100 microM. Activation of steroidogenesis by ATP was fully dependent on the presence of Ca2+ in the external medium. Among different nucleotides, only ATP, adenosine 5'-[gamma-thio]triphosphate, UTP, benzoylbenzoic-ATP and 2-methylthio-ATP were effective in inducing both the rise in [Ca2+]i and testosterone secretion. These effects were blocked by preincubation of Leydig cells with oxidized ATP, an inhibitor of the P2Z-purinergic receptor subtype. These results show that rat Leydig cells possess P2-purinergic receptors whose activation triggers an increase in [Ca2+]i due to the release of Ca2+ from internal stores and Ca2+ influx from the external medium. The stimulatory effect of extracellular ATP on testosterone secretion seems to be coupled to the influx of Ca2+ from the external medium.

Adenosine Triphosphate↗