RESUMEN
BACKGROUND: Calcium removal from the medium promptly reduces human sperm motility and induces a Na(+)-dependent depolarization that is accompanied by an increase in intracellular sodium concentration ([Na(+)](i)) and a decrease in intracellular calcium concentration ([Ca(2+)](i)). Sodium loading activates a Na(+)/K(+)-ATPase. METHODS: Membrane potential (Vm) and [Ca(2+)](i) were simultaneously detected in human sperm populations with the fluorescent probes diSC(3)(5) and fura 2. [Na(+)](i) and was measured independently in a similar fashion using sodium-binding benzofuran isophthalate. Motility was determined in a CASA system, ATP was measured using the luciferin-luciferase assay, and cAMP was measured by radioimmunoassay. RESULTS: Human sperm motility reduction after calcium removal is related to either Na(+)-loading or Na(+)-dependent depolarization, because, under conditions that inhibit the calcium removal-induced Na(+)-dependent depolarization and [Na(+)](i) increase, sperm motility was unaffected. By clamping sperm Vm with valinomycin, we found that the motility reduction associated with the calcium removal was related to sodium loading, and not to membrane potential depolarization. Mibefradil, a calcium channel blocker, markedly inhibited the Na(+)-dependent depolarization and sodium loading, and also preserved sperm motility. In the absence of calcium, both ATP and cAMP concentrations were decreased by 40%. However ATP levels were unchanged when calcium removal was performed under conditions that inhibit the calcium removal-induced Na(+)-dependent depolarization and [Na(+)](i) increase. CONCLUSIONS: Human sperm motility arrest induced by external calcium removal is mediated principally by sodium loading, which would stimulate the Na(+)/K(+)-ATPase and in turn deplete the ATP content.
Asunto(s)
Calcio/farmacología , Quelantes/farmacología , Sodio/metabolismo , Motilidad Espermática/efectos de los fármacos , Adenosina Trifosfato/química , Benzofuranos/farmacología , Colorantes/farmacología , AMP Cíclico/metabolismo , Éteres Cíclicos/farmacología , Fura-2/farmacología , Humanos , Concentración 50 Inhibidora , Masculino , Potenciales de la Membrana , Mibefradil/farmacología , Sodio/química , Espermatozoides/metabolismoRESUMEN
In human sperm, removal of external calcium produces a fast Na(+)-dependent depolarization that is presumably due to sodium permeation through calcium channels. Calcium restoration produces a ouabain-sensitive hyperpolarization that brings the membrane potential to values frequently more negative than resting. In this work, we show evidence indicating that external calcium removal induces an increase in the intracellular sodium ([Na(+)](i)) and that this phenomenon is related to the Na(+)-dependent depolarization. Calcium restoration blocked the [Na(+)](i) increase and then produced a slow decrease that was inhibited by ouabain. The [Na(+)](i) increase was inhibited by nanomolar-micromolar calcium or by millimolar magnesium, which has been previously shown to inhibit the Na(+)-dependent depolarization. This evidence supports the hypothesis that, in zero-calcium medium, a calcium channel that would contribute to resting intracellular calcium levels allows sodium permeation, producing depolarization and a significant [Na(+)](i) increase. Sodium loading would stimulate the Na(+),K(+)-ATPase, the activity of which contributes to the sperm hyperpolarization observed upon calcium restoration.
Asunto(s)
Calcio/metabolismo , Quelantes/farmacología , Ácido Egtácico/farmacología , Sodio/metabolismo , Espermatozoides/fisiología , Adulto , Calcio/farmacología , Membrana Celular/metabolismo , Inhibidores Enzimáticos/farmacología , Humanos , Magnesio/farmacología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Ouabaína/farmacología , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Espermatozoides/efectos de los fármacosRESUMEN
It is well known that extranodal NK/T-cell lymphoma (NK/TCL) nasal type clusters in Asian countries. A large series of 78 cases of nasal NK/TCL from Peru is analyzed in the present study. Two histologic groups 1 (monomorphic) and 2 (polymorphic), were segregated according to the proportion of large cells (above and below 30%, respectively). Catalyzed signal amplification technique was performed for enhancement of immunohistochemistry reactivities. Epstein-Barr virus (EBV) sequences and types were investigated using polymerase chain reaction. Clinical characteristics, stage, outcome, and response to treatment were evaluated in both groups. Fourteen cases (18%) and 64 cases (82%) corresponded to groups 1 and 2, respectively. Except for nasal obstruction, more common in group 2, all other symptoms were similar in both groups. Local extension and staging were also comparable. Both groups showed CD3c+ CD2+ CD56+ CD3s- CD20- immunophenotype. All cases were positive for EBV. In this series type-2 EBV was found more frequent than type-1 EBV, contrarily to that observed in Asian series. However, about one-third of cases simultaneously harbored both viral types. Both groups received an average of 50-Gy dose of radiation therapy (RT), with or without chemotherapy. Complete therapeutic response was achieved in 89% of group 1 and in 74% of group 2, but this difference was not statistically significant. There were no significant differences between the groups regarding disease-free survival, failure-free survival, relapse, and overall survival. The overall survival, in both groups, was longer for patients treated with RT alone compared with those treated with combined RT therapy and chemotherapy. The present study has shown that dividing nasal NK/TCL in monomorphic and polymorphic variants, according to frequency of large cells, does not correlate with clinical and prognostic factors.
Asunto(s)
Células Asesinas Naturales/patología , Linfoma de Células T/diagnóstico , Neoplasias Nasales/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Femenino , Herpesvirus Humano 4/genética , Humanos , Inmunohistoquímica/métodos , Inmunofenotipificación , Células Asesinas Naturales/virología , Linfoma de Células T/virología , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Neoplasias Nasales/virología , Perú/epidemiología , Reacción en Cadena de la Polimerasa , Resultado del TratamientoRESUMEN
Rat thymocytes showed two Na+/Mg2+ exchangers with high- and low- affinities for external Na+ (Na+o) at physiological internal Mg2+content. The total internal Mg2+ content (Mg2+it) was enhanced by loading with MgCl2 and the ionophore A-23187. Under these conditions, Na+/Mg2+ exchangers were dramatically stimulated by the Mg2+it increase. Na+-induced Mg2+ effluxes were independent of Cl-o or H+. The Na+/Mg2+ exchangers, which we named HANao (high affinity for Na+o) and LANao (low affinity for Na+o), were dissected in Mg2+-loaded thymocytes according to their kinetics and stoichiometries. HANao, which showed an apparent dissociation constant for Na+o (KNa H) = 9.2 +/- 1.6 mmol l(-1) Na+o and a maximal Na+ influx rate (VNa(Na H)max) = 30.5 +/- 6.1 mmol (l cells)(-1) h(-1), was a 1Na+:1Mg2+ simultaneous antiporter insensitive to external magnesium (Mg2+o) whereas that LANao, with KNa L = 65.1 +/- 8.6 mmol l(-1) Na+ and a VNa(Na L)max = 79.5 +/- 14.3 mmol (l cells)(-1) Na+ h(-1), was a 2Na+:1Mg2+ "ping-pong" antiporter which was strongly inhibited by Mg2+o. At physiological concentration of Mg2+o (1 mM), the Na+/Mg2+ exchange through the LANao was inhibited by approximately 50%. Amiloride (10(-4) M) inhibited at similar extent both Na+ and Mg2+ fluxes at high and at low Na+o.
Asunto(s)
Antiportadores/aislamiento & purificación , Magnesio/metabolismo , Sodio/metabolismo , Timo/citología , Amilorida/farmacología , Animales , Antiportadores/metabolismo , Masculino , Ratas , Ratas Wistar , Bloqueadores de los Canales de Sodio/farmacología , Timo/efectos de los fármacosRESUMEN
Peroxynitrite, the product of the reaction between *NO and O2*-, is a strong oxidant and nitrating molecule, and it has been recently consideredas a component of some important signaling pathways. Herein, we report the effect of peroxynitrite on glucose uptake in 3T3-L1 adipocytes. Peroxynitrite stimulated glucose uptake and this effect was inhibited by citochalasin B, indicating the participation of facilitated GLUT transporters. Peroxynitrite-induced glucose uptake was not related to intracellular ATP, nor to external or internal calcium, but it was inhibited by the phosphatidylinositol 3-kinase (PI3-K) inhibitor, wortmannin. Additionally, we also found that peroxynitrite did not activate the insulin receptor nor the PI3-K downstream signaling protein kinase B (PKB/Akt). The dose-dependent inhibitory action of wortmannin suggests that peroxynitrite activates glucose transport without affecting GLUT transporters translocation.
Asunto(s)
Adipocitos/enzimología , Glucosa/farmacocinética , Ácido Peroxinitroso/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Células 3T3-L1 , Adenosina Trifosfato/metabolismo , Androstadienos/farmacología , Animales , Calcio/metabolismo , Supervivencia Celular , Citocalasina B/farmacología , Relación Dosis-Respuesta a Droga , Glucosa/metabolismo , Ratones , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , WortmaninaRESUMEN
The regulation of the cytosolic free magnesium concentration ([Mg2+]i) is a fundamental cellular process that requires magnesium extruding mechanisms. Here, we present evidence indicating that rat thymocytes are endowed with different Na/Mg exchange systems. Fluxes of magnesium were measured using the fluorescent magnesium indicator magfura-2. Cells were loaded with magnesium using the calcium ionophore A-23187 to 0.6-8.0 mM [Mg2+]i (resting [Mg2+]i = 0.38 +/- 0.06 mM, n = 5). The presence of extracellular sodium was required for magnesium exit. The initial rate of [Mg2+]i was stimulated by extracellular sodium with Michaelis-Menten kinetics. The Vmax of the sodium-dependent magnesium exit was markedly increased by [Mg2+]i. Holding the membrane potential at either -84 mV or at -10 mV had different effects on the sodium-stimulated magnesium efflux, depending on the extracellular sodium concentration ([Na+]o). At 10-30 mM [Na+]o, the magnesium efflux was faster at -10 mV than at -84 mV. Conversely, at 50-200 mM [Na+]o, the efflux of magnesium was faster at -84 mV that at -10 mV. At 75 mM [Na+]o, the activities where nearly the same at both membrane potential values. These observations suggest that the stochiometry of the Na+/Mg2+ exchange changes with [Na+]o.
Asunto(s)
Magnesio/metabolismo , Sodio/farmacología , Timo/metabolismo , Animales , Células Cultivadas , Fluorometría , Transporte Iónico/efectos de los fármacos , Cinética , Masculino , Potenciales de la Membrana , Ratas , Ratas Wistar , Sodio/metabolismo , Timo/citología , Timo/fisiologíaRESUMEN
Progesterone induces calcium influx and acrosomal exocytosis in human sperm. Pharmacologic evidence suggests that voltage-dependent calcium channels (VDCCs) are involved. In this study, membrane potential (Vm) and intracellular calcium concentration ([Ca(2+)](i)) were monitored simultaneously to assess the effect of VDCC gating on the calcium influx triggered by progesterone. Holding the Vm to values that maintained VDCCs in a deactivated (-71 mV) closed state inhibited the calcium influx induced by progesterone by approximately 40%. At this Vm, the acrosomal reaction induced by progesterone, but not by A23187, was inhibited. However, when the Vm was held at -15 mV (which maintains VDCCs in an inactivated closed state), the progesterone-induced calcium influx was stimulated. Furthermore, the progesterone and voltage-dependent calcium influxes were additive. These findings indicate that progesterone does not produce VDCC gating in human sperm.
Asunto(s)
Canales de Calcio/fisiología , Calcio/metabolismo , Activación del Canal Iónico/efectos de los fármacos , Progesterona/farmacología , Espermatozoides/efectos de los fármacos , Espermatozoides/fisiología , Reacción Acrosómica/efectos de los fármacos , Reacción Acrosómica/fisiología , Adolescente , Adulto , Humanos , Ionóforos/farmacología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Valinomicina/farmacologíaRESUMEN
Hydroa-like cutaneous T-cell lymphoma (hydroa-like CTCL) is an unusual pediatric malignancy with a poor prognosis. An impressive cutaneous rash characterized by edema, blisters, ulcers, crusts, and scars, resembling hidroa vacciniforme, is seen mainly on the face and sometimes on the extremities. The lesion consists of lymphomatous T-cell infiltration of the skin and subcutis with variable exocytosis and angiocentricity. It has been also called edematous, scarring vasculitic panniculitis and hydroa-like lymphoma. An association with Epstein-Barr virus has been suggested. The differential diagnosis includes other cutaneous lymphomas, particularly the cutaneous nasal type T/natural killer-cell lymphoma, mycosis fungoides, precursor T-cell lymphoblastic lymphoma, nonspecific peripheral T-cell lymphoma, cutaneous anaplastic large cell lymphoma, and subcutaneous panniculitic T-cell lymphoma. Other differential diagnoses are inflammatory dermatopathies and panniculitides. Based on a series of 16 such cases referred to the Institute of Neoplastic Diseases, the objective of this report is not only to provide a better clinicopathologic understanding of this entity but also a reappraisal of it as a malignancy. The male/female frequency ratio was 1:1. The median age was 10 years old. All cases showed predominant facial involvement with edema, blisters, ulcers, crusts, and scars. Chemotherapy and/or radiotherapy had little or no benefit. The prognosis was usually dismal. The lymphoma extended from the epidermis to the subcutis, with frequent angiocentric and periadnexal array. Lymphoma cells were mostly of intermediate size with dense hyperchromatic nuclei, inconspicuous nucleoli, and infrequent mitosis. A scanty and variable inflammatory background was found. The lymphoma cells displayed T-cell cytotoxic phenotype. In addition, they were negative for the natural killer cell antigens CD56 and CD57. Epstein-Barr virus in situ hybridization was positive in the six cases in which it was assayed. T-cell receptor gamma (TCRgamma) displayed monoclonal-type rearrangement in four cases studied. Our findings indicate that hydroa-like CTCL is an independent clinicopathologic entity that affects children. Consequently, it should be considered an independent subset of CTCLs and be included as such in the classification of neoplastic diseases of the lymphoid tissues.
Asunto(s)
Linfoma de Células T/genética , Linfoma de Células T/patología , Neoplasias Cutáneas/genética , Neoplasias Cutáneas/patología , Adolescente , Niño , Preescolar , Diagnóstico Diferencial , Femenino , Humanos , Inmunofenotipificación , Hibridación in Situ , Linfoma de Células T/diagnóstico , Linfoma de Células T/inmunología , Masculino , Perú , Neoplasias Cutáneas/diagnóstico , Neoplasias Cutáneas/inmunologíaRESUMEN
We have reviewed clinically, morphologically, and immunophenotypically a series of 14 Epstein-Bar virus (EBV)+ cutaneous natural killer cell (NK)/T-cell lymphoma from Peru. Most (11 out of 14) of these cases fit well into the category of Hydroa vacciniforme-like lymphoma (HVLL), but 3 have a different clinical presentation, without facial involvement. In all 14 cases, skin lesions present in both the sun-exposed and nonexposed areas exhibited a slowly progressive relapsing course, changing from edema, to blistering, ulceration, and final scarring. The immunophenotype had a cytotoxic T or NK-cell lineage. The mean time of disease before admission to hospital was 69 months (range, 6 mo to 31 y). Only 2 patients had fever, hepatosplenomegaly, systemic lymphadenopathy, and a high lactate dehydrodenage (LDH) level at the time of diagnosis, whereas 10 had facial swelling. After treatment, only 4 patients remain alive, although with persistent disease. Ten patients died after a mean follow-up of 11.6 months after the initial diagnosis (range, 1 to 32 mo), because of concurrent infections (4 cases), disease progression (4 patients) or both (2 patients). Endemic Epstein-Bar virus (EBV)-positive cutaneous NK/T-cell lymphoproliferative disorders in childhood and early adulthood are characterized by a protracted clinical course, eventually leading to an aggressive phase characterized by concurrent infections and disease progression.
Asunto(s)
Infecciones por Virus de Epstein-Barr/patología , Hidroa Vacciniforme/patología , Células Asesinas Naturales/patología , Linfoma Cutáneo de Células T/patología , Neoplasias Cutáneas/patología , Linfocitos T/patología , Adolescente , Adulto , Biomarcadores de Tumor/metabolismo , Niño , Preescolar , Células Clonales , Infecciones por Virus de Epstein-Barr/inmunología , Infecciones por Virus de Epstein-Barr/mortalidad , Femenino , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/aislamiento & purificación , Humanos , Hidroa Vacciniforme/inmunología , Hidroa Vacciniforme/mortalidad , Hibridación in Situ , Células Asesinas Naturales/inmunología , Linfoma Cutáneo de Células T/inmunología , Linfoma Cutáneo de Células T/mortalidad , Masculino , Perú/epidemiología , Piel/patología , Piel/virología , Neoplasias Cutáneas/inmunología , Neoplasias Cutáneas/mortalidad , Tasa de Supervivencia , Linfocitos T/inmunología , Adulto JovenRESUMEN
Progesterone induces a fast transient calcium influx in human sperm though the activation of nongenomic receptors. During sperm capacitation, a complex process required for sperm to be able to fertilize the egg, the calcium influx induced by progesterone is enhanced. Sperm capacitation is mediated by an increase in cAMP content and subsequent protein kinase A (PKA) activation. In this work, we examined the effect of increasing intracellular cAMP on the calcium influx induced by progesterone in noncapacitated human sperm. To do this, sperm were exposed to the phosphodiesterase inhibitor papaverine for 5 minutes, a treatment that increased both the cAMP content and the PKA activity several-fold. The calcium influx induced by progesterone was increased by papaverine to levels close to those found in capacitated sperm. This effect was partially inhibited by H89 (48%) and by genistein (41%), and the sum of both inhibitors reduced the stimulating effect of papaverine by 89%. The inhibitory effect of genistein on the progesterone-induced calcium influx could be related to its capability to inhibit the papaverine-stimulated increase in cAMP content and PKA activity. The results presented here suggest that the calcium influx induced by progesterone is up-regulated by the PKA activity.
Asunto(s)
Calcio/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Papaverina/farmacología , Inhibidores de Fosfodiesterasa/farmacología , Progesterona/metabolismo , AMP Cíclico/metabolismo , Humanos , Técnicas In Vitro , Masculino , Espermatozoides/efectos de los fármacos , Espermatozoides/metabolismoRESUMEN
Human sperm are endowed with voltage-dependent calcium channels (VDCC) that produce increases in [Ca2+]i in response to depolarization with KCl. These channels are stimulated during "capacitation", a complex biochemical process, accompanied by a slight pHi alkalization, that sperm must accomplish to acquire the ability to fertilize the egg. The stimulation can be explained in part by the fact that in non-capacitated sperm, calcium influx through VDCC is stimulated by pHi alkalization in the range of pHi observed during capacitation. In this work, we explored the effect of pHi on VDCC in capacitated sperm loaded with fura ff. Strikingly, the pHi sensitivity of VDCC increased approximately 7-fold when sperm was capacitated, as compared with non-capacitated sperm. This finding suggests that the pHi sensitivity of VDCC can be modulated during capacitation so that a combined effect of pHi alkalization and biochemical regulation enhances calcium influx through these channels.
Asunto(s)
Álcalis/farmacología , Canales de Calcio/efectos de los fármacos , Calcio/metabolismo , Capacitación Espermática/fisiología , Espermatozoides/fisiología , Adolescente , Adulto , Cloruro de Amonio/farmacología , Canales de Calcio/fisiología , Colorantes Fluorescentes/análisis , Fura-2/análogos & derivados , Fura-2/análisis , Humanos , Concentración de Iones de Hidrógeno , Transporte Iónico/efectos de los fármacos , Masculino , Espermatozoides/efectos de los fármacosRESUMEN
Removal of external calcium with EGTA (from 2.5 mm to nanomolar levels) caused a remarkable depolarization in human sperm. This depolarization was initially fast. It was followed by a slow phase that brought the Vm to values of over 0 mV in 1-2 min. The slow and sustained phase correlated with a sustained decrease in intracellular calcium. However, calcium removal still induced depolarization in sperm with enhanced intracellular calcium (induced by progesterone), indicating that the sustained depolarization was not caused by a sustained intracellular calcium decrease. The depolarization was reduced as the external sodium content was substituted with choline, indicating that it was due to a sodium current, and was observed in lithium but not in tetramethylammonium-containing medium. In low sodium medium, the addition of sodium after calcium removal induced depolarization to the extent of which slightly increased in 2 min. The depolarization was completely inhibited by external magnesium (Ki = 1.16 mm). The addition of calcium or magnesium to calcium removal-induced depolarized sperm induced hyperpolarization that was inhibited by ouabain and was also prevented in medium without potassium, suggesting that the activity of the electrogenic Na+,K+-ATPase was involved. The conductance activated by calcium removal might unveil the presence of a calcium channel that in the absence of external calcium allows sodium permeation and that in normal conditions might contribute to the resting intracellular calcium concentration.
Asunto(s)
Calcio/metabolismo , Sodio/metabolismo , Espermatozoides/metabolismo , Adolescente , Adulto , Calcio/farmacología , Calibración , Quelantes/farmacología , Relación Dosis-Respuesta a Droga , Ácido Egtácico/farmacología , Electrofisiología , Estimulantes Ganglionares/farmacología , Humanos , Cinética , Litio/farmacología , Magnesio/química , Magnesio/farmacología , Masculino , Potenciales de la Membrana , Progesterona/metabolismo , Compuestos de Amonio Cuaternario/farmacología , Sodio/farmacología , ATPasa Intercambiadora de Sodio-Potasio/metabolismoRESUMEN
Human sperm are endowed with putative voltage-dependent calcium channels (VDCC) that produce measurable increases in intracellular calcium concentration ([Ca(2+)](i)) in response to membrane depolarization with potassium. These channels are blocked by nickel, inactivate in 1-2 min in calcium-deprived medium, and are remarkably stimulated by NH(4)Cl, suggesting a role for intracellular pH (pH(i)). In a previous work, we showed that calcium permeability through these channels increases approximately onefold during in vitro "capacitation," a calcium-dependent process that sperm require to fertilize eggs. In this work, we have determined the pH(i) dependence of sperm VDCC. Simultaneous depolarization and pH(i) alkalinization with NH(4)Cl induced an [Ca(2+)](i) increase that depended on the amount of NH(4)Cl added. VDCC stimulation as a function of pH(i) showed a sigmoid curve in the 6.6-7.2 pH(i) range, with a half-maximum stimulation at pH approximately 7.00. At higher pH(i) (> or =7.3), a further stimulation occurred. Calcium release from internal stores did not contribute to the stimulating effect of pH(i) because the [Ca(2+)](i) increase induced by progesterone, which opens a calcium permeability pathway that does not involve gating of VDCC, was unaffected by ammonium. The ratio of pH(i)-stimulated-to-nonstimulated calcium influx was nearly constant at different test depolarization values. Likewise, depolarization-induced calcium influx in pH(i)-stimulated and nonstimulated cells was equally blocked by nickel. In our capacitating conditions pH(i) increased 0.11 pH units, suggesting that the calcium influx stimulation observed during sperm capacitation might be partially caused by pH(i) alkalinization. Additionally, a calcium permeability pathway triggered exclusively by pH(i) alkalinization was detected.
Asunto(s)
Calcio/metabolismo , Concentración de Iones de Hidrógeno , Capacitación Espermática/fisiología , Espermatozoides/metabolismo , Cloruro de Amonio/farmacología , Calcio/farmacocinética , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio/metabolismo , Estimulación Eléctrica , Humanos , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Níquel/farmacologíaRESUMEN
To fertilize, mammalian sperm must undergo two sequential steps that require activation of calcium entry mechanisms, capacitation and acrosomal exocytosis, induced in the latter case by the egg zona pellucida glycoprotein ZP3 or by progesterone. Voltage-dependent calcium channels (VDCC) could participate in these processes. Since patch clamp recordings are extremely difficult in mature sperm, the activity of VDCC has been alternatively analyzed with optical detectors of membrane potential and intracellular calcium in sperm populations. Using this approach, we previously reported that in human sperm there is a voltage-dependent calcium influx system that strongly indicates that human sperm are endowed with functional VDCC. In this study we developed evidence indicating that calcium influx through VDCC is significantly stimulated during sperm in vitro capacitation and by progesterone action, which is present in the follicular fluid that surrounds the egg. The observed effects of capacitation and progesterone on VDCC may be physiologically significant for sperm-egg interaction.