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1.
Curr Oncol ; 25(6): e527-e532, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30607119

RESUMO

Background: Fertility preservation is an important concern in breast cancer patients. In the present investigation, we set out to create a specific protocol of controlled ovarian stimulation (cos) for oocyte cryopreservation in breast cancer patients. Methods: From November 2014 to December 2016, 109 patients were studied. The patients were assigned to a specific random-start ovarian stimulation protocol for oocyte cryopreservation. The endpoints were the numbers of oocytes retrieved and of mature oocytes cryopreserved, the total number of days of ovarian stimulation, the total dose of gonadotropin administered, and the estradiol level on the day of the trigger. Results: Mean age in this cohort was 31.27 ± 4.23 years. The average duration of cos was 10.0 ± 1.39 days. The mean number of oocytes collected was 11.62 ± 7.96 and the mean number of vitrified oocytes was 9.60 ± 6.87. The mean estradiol concentration on triggering day was 706.30 ± 450.48 pg/mL, and the mean dose of gonadotropins administered was 2610.00 ± 716.51 IU. When comparing outcomes by phase of the cycle in which cos was commenced, we observed no significant differences in the numbers of oocytes collected and vitrified, the length of ovarian stimulation, and the estradiol level on trigger day. The total dose of follicle-stimulating hormone and human menopausal gonadotropin administered was statistically greater in the group starting cos in the luteal phase than in the group starting in the late follicular phase. Conclusions: Our results suggest that using a specific protocol with random-start ovarian stimulation for oocyte cryopreservation in breast cancer patients is effective and could be offered to young women undergoing oncologic treatment.


Assuntos
Neoplasias da Mama , Criopreservação , Preservação da Fertilidade , Indução da Ovulação , Adulto , Criopreservação/métodos , Feminino , Preservação da Fertilidade/métodos , Hormônio Liberador de Gonadotropina/administração & dosagem , Gonadotropinas/administração & dosagem , Humanos , Oócitos/citologia , Oócitos/metabolismo , Indução da Ovulação/métodos
2.
Med Hypotheses ; 78(4): 442-5, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22284634

RESUMO

Infertility represents one of the main long-term consequences of the chemotherapy used for the adjuvant treatment of breast cancer. Approximately 60-65% of breast cancers express the nuclear hormone receptor in premenopausal women. Adjuvant endocrine therapy is an integral component of care for patients with hormone receptor-positive (HR+) tumours. The GnRH agonist (GnRHa) alone or in combination with tamoxifen produces results at least similar to those obtained with the different chemotherapy protocols in patients with HR+ breast cancer with respect to recurrence-free survival and overall survival. It is time to indicate adjuvant therapy with GnRHa associated with tamoxifen for patients with breast cancer (HR+ tumours) if they want to preserve their reproductive function. The evaluation of ovarian reserve tests: follicle stimulating hormone (FSH), anti-Mullerian hormone (AMH), inhibin B, antral follicle count (AFC) and ovarian volume 6 months, and 1 year after the end of therapy with GnRHa/tamoxifen must be realised. The recurrence-free survival and overall survival should be analysed. The major implication of this hypothesis will be to avoid adjuvant chemotherapy for patients with breast cancer (HR+ tumours) that request fertility preservation. It is expected that ovarian function should not be altered in almost all cases and subsequent pregnancy a real possibility.


Assuntos
Neoplasias da Mama/tratamento farmacológico , Quimioterapia Adjuvante/métodos , Hormônio Liberador de Gonadotropina/agonistas , Infertilidade Feminina/prevenção & controle , Receptores Citoplasmáticos e Nucleares/metabolismo , Tamoxifeno/uso terapêutico , Quimioterapia Adjuvante/efeitos adversos , Feminino , Humanos , Pré-Menopausa
3.
Int J Androl ; 35(1): 46-51, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21535011

RESUMO

The aim of this investigation was to determine the presence of abnormal sperm chromatin packaging in spermatozoa with large nuclear vacuoles (LNV) selected via high magnification by analysing the pattern of chromomycin A3 (CMA3) staining. A prospective observational study was designed to analyse semen samples obtained from 66 men undergoing infertility diagnosis and treatment. The numbers of cells with normal (dull yellow staining of the sperm head/CMA3-negative) and abnormal (bright yellow fluorescence of the sperm head/CMA3-positive) chromatin packaging were determined on slides with normal and LNV spermatozoa. The presence of bright yellow fluorescence (CMA3-positive) was significantly higher (p < 0.0001) in spermatozoa with LNV than in normal spermatozoa (719/1351; 53.2% vs. 337/835; 40.3%, respectively), reflecting a higher percentage of abnormal chromatin packaging in spermatozoa with large LNV. Our data support the hypothesis that the presence of LNV reflects the presence of abnormal chromatin packaging, which may facilitate sperm DNA damage. As sperm nuclear vacuoles are evaluated more precisely at high magnifications using motile sperm organelle morphology examination (MSOME), the present results support the use of high-magnification sperm selection for intracytoplasmic sperm injection (ICSI).


Assuntos
Cromatina/metabolismo , Espermatozoides/metabolismo , Vacúolos/metabolismo , Adulto , Humanos , Masculino
4.
Reprod Biomed Online ; 22(6): 583-9, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21507722

RESUMO

Birefringence or double refraction is the decomposition of a ray of light into two rays when it passes through an anisotropic material such as quartz. Sperm cells have been demonstrated to be optically anisotropic. The objective of this study was to evaluate the relationship between the pattern of human sperm head birefringence (SHBF) and DNA damage. A total of 26 patients with normal semen were included. DNA damage (fragmentation and denaturation) was evaluated in the sperm head in the context of birefringence, both total (SHBF-T) and partial (SHBF-P), by terminal deoxyribonucleotidyl transferase (TdT)-mediated dUDP nick-end labelling assay and acridine orange fluorescence, respectively. Positive DNA fragmentation in spermatozoa with SHBF-T (205/1053; 19.5%) was significantly higher (P<0.0001) than in spermatozoa that presented SHBF-P (60/820; 7.3%). However, the percentage of denatured DNA in spermatozoa with SHBF-T (824/1256; 65.6%) was not significantly different from the ones with SHBF-P (666/1009; 66.0%). In conclusion, the data support a positive relationship between spermatozoa with total SHBF in their head and increased DNA fragmentation.


Assuntos
Birrefringência , Dano ao DNA , Cabeça do Espermatozoide , Adulto , Fragmentação do DNA , Humanos , Marcação In Situ das Extremidades Cortadas , Infertilidade Masculina/patologia , Masculino , Pessoa de Meia-Idade , Desnaturação de Ácido Nucleico , Motilidade dos Espermatozoides , Espermatozoides
5.
Reprod Biomed Online ; 14(1): 14-25, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17207326

RESUMO

This study aims to compare the efficacy of recombinant LH (rLH) supplementation for ovarian stimulation in gonadotrophin-releasing hormone-antagonist protocol for IVF/intracytoplasmic sperm injection cycles. Search strategies included online surveys of databases. The fixed effects model was used for odds ratio (OR) and effect size (weighted mean difference, WMD). Five trials fulfilled the inclusion criteria. When the meta-analysis was carried out, advantages were observed for the LH supplementation protocol with respect to higher serum oestradiol concentrations on the day of human chorionic gonadotrophin administration P < 0.0001; WMD: 514, 95% CI 368, 660) and higher number of mature oocytes (P = 0.0098; WMD: 0.88, 95% CI 0.21, 1.54). However, these differences were not observed in the total amount of recombinant FSH (rFSH) administered, days of stimulation, number of oocyets retrieved, the clinical pregnancy rate per oocyte retrieval, the implantation rate and miscarriage rate. This result demonstrates that the association of rLH with rFSH may prevent any decrease in oestradiol after antagonist administration and that a significantly higher number of mature oocytes was available for laboratory work. Nevertheless, it failed to show any statistically significant difference in clinically significant end-points in IVF (implantation and pregnancy rates). Additional randomized controlled trials are needed to confirm these results further.


Assuntos
Fertilização in vitro , Hormônio Foliculoestimulante/uso terapêutico , Hormônio Liberador de Gonadotropina/antagonistas & inibidores , Hormônio Luteinizante/uso terapêutico , Indução da Ovulação , Estradiol/sangue , Feminino , Fertilização in vitro/normas , Hormônio Foliculoestimulante/genética , Humanos , Hormônio Luteinizante/genética , Hormônio Luteinizante/normas , Gravidez , Taxa de Gravidez , Ensaios Clínicos Controlados Aleatórios como Assunto , Proteínas Recombinantes/uso terapêutico , Injeções de Esperma Intracitoplásmicas/normas , Resultado do Tratamento
6.
Reprod Biomed Online ; 13(5): 618-27, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17169170

RESUMO

The aim of this meta-analysis was to compare the efficacy of gonadotrophin antagonist (GnRH-ant) versus GnRH agonist (GnRHa) as coadjuvant therapy for ovarian stimulation in poor ovarian responders in IVF/intracytoplasmic sperm injection cycles. Search strategies included on-line surveys of databases such as MEDLINE , EMBASE and others. A fixed effects model was used for odds ratio (OR) and effect size (weighted mean difference, WMD). Six trials fulfilled the inclusion criteria (randomized controlled trials). There was no difference between GnRH-ant and GnRHa (long and flare-up protocols) with respect to cycle cancellation rate, number of mature oocytes and clinical pregnancy rate per cycle initiated, per oocyte retrieval and per embryo transfer. When the meta-analysis was applied to the two trials that had used GnRH-ant versus long protocols of GnRHa, a significantly higher number of retrieved oocytes was observed in the GnRH-ant protocols [P=0.018; WMD: 1.12 (0.18, 2.05)]. However, when the meta-analysis was applied to the four trials that had used GnRH-ant versus flare-up protocols, a significantly higher number of retrieved oocytes (P=0.032; WMD: -0.51, 95% CI -0.99, -0.04) was observed in the GnRHa protocols. Nevertheless, additional randomized controlled trials with better planning are needed to confirm these results.


Assuntos
Fármacos para a Fertilidade Feminina/uso terapêutico , Fertilização in vitro/efeitos dos fármacos , Hormônio Liberador de Gonadotropina/agonistas , Hormônio Liberador de Gonadotropina/antagonistas & inibidores , Infertilidade Feminina/tratamento farmacológico , Indução da Ovulação/métodos , Esquema de Medicação , Feminino , Fertilização in vitro/métodos , Humanos , Razão de Chances , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do Tratamento
7.
Reprod Biomed Online ; 13(4): 541-6, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17007675

RESUMO

A total of 63 pregnancies (47 singleton, 15 twin, 1 triplet) from intracytoplasmic sperm injection cycles were analysed. In all embryo transfers, the catheter was introduced into the endometrial cavity guided by abdominal ultrasound, with the catheter tip placed at the middle point of the endometrial cavity. Gestational sacs (GS) were located 21-24 days after transfer (gestational age=5 weeks) by two-dimensional and three-dimensional transvaginal ultrasound. The uterine cavity was divided into three parts: upper, middle and lower. Furthermore, the upper region was subdivided into right, middle and left areas, and the middle region was subdivided into right and left areas. The frequency of gestational sacs in each area was evaluated. In singleton pregnancies 66.0% (31/47) of the GS were detected in the upper region, 29.8% (14/47) in the middle region and 4.2% (2/47) in the lower region. In multiple pregnancies (twins and triplet) 45.5% (15/33) of the GS were detected in the upper region, 51.5% (17/33) in the middle region and 3.0% (1/33) in the lower region. In conclusion, the results demonstrate that when embryos are transferred to the central area of the uterine cavity there is an increase in implantation rate in the middle region compared with the rate expected in naturally conceived pregnancies (9-15%).


Assuntos
Implantação do Embrião , Transferência Embrionária , Útero/anatomia & histologia , Aborto Espontâneo , Adulto , Feminino , Humanos , Gravidez , Gravidez Múltipla , Injeções de Esperma Intracitoplásmicas , Ultrassonografia Pré-Natal/métodos , Útero/diagnóstico por imagem
8.
Reprod Biomed Online ; 11(1): 64-70, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16102290

RESUMO

The outcomes of 1028 assisted reproductive technology cycles were studied retrospectively, considering two different periods of embryo transfer. In the first period, 262 cycles in women < 36 years old were studied, in which three embryos were transferred, followed by 157 cycles in women > or = 36 years, in which four embryos were transferred. In the second period, 332 cycles were evaluated in women < 36 years and 277 cycles in women > or = 36 years old, reducing the number of embryos transferred to two and three respectively. Embryos were only scored morphologically, and the best embryos were chosen for transfer. In the first period, in women < 36 years old, a clinical pregnancy rate of 55.7% was achieved, compared with 42.5% in the second period (P < 0.01). In women > or = 36 years old, the first period of embryo transfer showed a clinical pregnancy rate of 39.5%, compared with 28.5% in the second period (P < 0.01). The number of twin pregnancies in the three groups of patients in whom one to four embryos were transferred was not significantly different (24.2, 28.4, 24.8%). It is concluded that even with the biases induced by a retrospective study, the reduction in the number of embryos transferred, from three to two in women < 36 years of age, and from four to three in women > or = 36 years of age, without any selection other than pre-transfer morphological score, adversely affects the outcome of treatment, without a significant reduction in twin gestation rate. Other strategies are to be implemented in gametes and embryo selection, and patients must be aware that, even with a reduction in pregnancy rate, the goal is to achieve a high cumulative pregnancy rate, reducing the complications induced by multiple pregnancies.


Assuntos
Transferência Embrionária , Técnicas de Reprodução Assistida , Adulto , Implantação do Embrião , Feminino , Fertilização in vitro/métodos , Hormônio Foliculoestimulante/sangue , Humanos , Idade Materna , Gravidez , Resultado da Gravidez , Taxa de Gravidez , Gravidez Ectópica/epidemiologia , Gravidez Múltipla/estatística & dados numéricos , Estudos Retrospectivos , Resultado do Tratamento
9.
Placenta ; 24 Suppl B: S20-6, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14559026

RESUMO

Embryo transfer has received little clinical attention and has been, until recently, the most inefficient step in in-vitro fertilization (IVF). In this article, the authors review the literature and their personal experience regarding the process of intrauterine transfer of embryos, which remains the object of much discussion. Factors which appear to influence implantation rates are: contamination of the catheter tip with cervical bacteria, stimulation of uterine contractions during the procedure, the type of catheter, ultrasound guidance during the transfer, and the position of the embryos in the uterine cavity. Easy and atraumatic transfer is essential for successful implantation and the embryos need to be placed in the middle of the cavity, away from the fundus. Knowing, beforehand, the position and length of the uterus can provide better results and may reduce the rate of ectopic pregnancies. Evidence from randomized studies has supported this claim. Despite the number of available studies controlling certain variables, most authors, even using the same catheter, ultrasound guidance and/or a trial transfer use different protocols or similar instruments in different ways. Standardization of the transcervical intrauterine transfer of embryos in a large randomized study is needed before definitive conclusions can be drawn. The goal of improved implantation and pregnancy rates deserve these efforts.


Assuntos
Implantação do Embrião/fisiologia , Transferência Embrionária , Fertilização in vitro , Feminino , Humanos
10.
Placenta ; 24 Suppl B: S39-47, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14559029

RESUMO

Implantation is a phenomenon that involves an interaction between the embryo and maternal endometrium. There is, in the menstrual cycle, a short and precise period of time in which the maternal-embryonic interaction is optimal and culminates with adhesion and invasion of the blastocyst into the progesterone-induced secretory endometrium. This period is called nidation or implantation window. In the implantation window changes occur in endometrial epithelial morphology, characterized by the appearance of membrane projections called pinopodes. Pinopodes are progesterone-dependent organelles, that look like apical cellular protrusions appearing between days 20 and 21 of the natural menstrual cycle. There are many factors that regulate the changes typical of the implantation window and the appearance of the pinopodes. The embryonic and maternal expression of growth factors and cytokines, calcitonin, HOX genes and cell adhesion molecules might all play a major role in the phenomenon of implantation. The cytokines function as chemical messengers and can serve as biomarkers of uterine receptivity. Understanding the function of these biomarkers and their role in determining the implantation window in women, will help us to diagnose and treat infertile couples more efficiently.


Assuntos
Blastocisto/fisiologia , Implantação do Embrião/fisiologia , Endométrio/fisiologia , Gravidez/fisiologia , Biomarcadores/análise , Feminino , Humanos
11.
Circ Res ; 88(4): 415-21, 2001 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-11230109

RESUMO

Collateral effects of exogenous sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA) expression were characterized in neonatal rat and chicken embryo cardiac myocytes, and the conditions required to produce acceleration of Ca(2+) transients with minimal toxicity were established. Cultured myocytes were infected with adenovirus vector carrying the cDNA of wild-type SERCA1, an inactive SERCA1 mutant, or enhanced green fluorescence protein under control of the cytomegalovirus promoter. Controls were exposed to empty virus vector. Each group was tested with and without phenylephrine (PHE) treatment. Under conditions of limited calf-serum exposure, the infected rat myocytes manifested a more rapid increase in size, protein content, and rate of protein synthesis relative to noninfected controls. These changes were not accompanied by reversal to fetal transcriptional pattern (as observed in hypertrophy triggered by PHE) and may be attributable to facilitated exchange with serum factors. SERCA virus titers >5 to 6 plaque-forming units per cell produced overcrowding of ATPase molecules on intracellular membranes, followed by apoptotic death of a significant number of rat but not chicken myocytes. Enhanced green fluorescence protein virus and empty virus also produced cytotoxic effects but at higher titers than SERCA. Expression of exogenous SERCA and enhancement of Ca(2+) transient kinetics could be obtained with minimal cell damage in rat myocytes if the SERCA virus titer were maintained within 1 to 4 plaque-forming units per cell. Expression of endogenous SERCA was unchanged, but expression of exogenous SERCA was higher in myocytes rendered hypertrophic by treatment with PHE than in nontreated controls.


Assuntos
ATPases Transportadoras de Cálcio/genética , Miocárdio/citologia , Adenoviridae/genética , Animais , Western Blotting , Cálcio/metabolismo , ATPases Transportadoras de Cálcio/biossíntese , Divisão Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Embrião de Galinha , Fragmentação do DNA , DNA Complementar/metabolismo , Expressão Gênica , Técnicas de Transferência de Genes , Vetores Genéticos , Cinética , Microscopia de Contraste de Fase , Fenilalanina/farmacologia , RNA Mensageiro/metabolismo , Ratos , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático , Tapsigargina/farmacologia
12.
J Physiol ; 528 Pt 1: 53-63, 2000 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-11018105

RESUMO

1. Sarco-endoplasmic reticulum Ca2+-ATPase from fast skeletal (SERCA1) or cardiac muscle (SERCA2a) was expressed in embryonic chicken and neonatal rat cardiac myocytes by adenovirus vectors, with c-myc tags on both constructs to compare expression and distinguish exogenous from endogenous SERCA2a in myocytes. 2. Expression of the two isoforms was similar (approximately 3-fold higher than endogenous SERCA). However, SERCA1 activity was 2-fold greater than SERCA2a activity, due to intrinsic differences in turnover rates. Activation of both exogenous SERCA isoforms by Ca2+ was displaced to slightly lower [Ca2+], suggesting that the overexpressed isoforms were independent of phospholamban. In fact, phospholamban and calsequestrin expression were unchanged. 3. Decay time constants of cytosolic Ca2+ transients from cells overexpressing SERCA1 were reduced by 30-40 % and half-widths by 10-15 % compared to controls. SERCA2a overexpression produced much less acceleration of transients in chick than in rat, and less acceleration than SERCA1 overexpression in either species. There was no significant change in resting [Ca2+], peak amplitudes, or in the amount of Ca2+ releasable by caffeine from overexpression of either SERCA isoform. However, the amplitudes of the transients increased with SERCA1 overexpression when pacing frequency limited refilling of the sarcoplasmic reticulum. 4. It is concluded that total SERCA transport velocity has a primary effect on the decay phase of transients. Transport velocity is affected by SERCA isoform turnover rate, temperature, and/or SERCA copy number.


Assuntos
ATPases Transportadoras de Cálcio/metabolismo , Cálcio/metabolismo , Miocárdio/metabolismo , Animais , Animais Recém-Nascidos , Cafeína/farmacologia , Cálcio/farmacocinética , Proteínas de Ligação ao Cálcio/biossíntese , ATPases Transportadoras de Cálcio/genética , Calsequestrina/biossíntese , Compartimento Celular , Células Cultivadas , Embrião de Galinha , Citosol/metabolismo , Corantes Fluorescentes , Dosagem de Genes , Expressão Gênica/genética , Vetores Genéticos/genética , Transporte de Íons/efeitos dos fármacos , Isoenzimas/genética , Isoenzimas/metabolismo , Miocárdio/citologia , Ratos , Tempo de Reação/fisiologia , Reprodutibilidade dos Testes , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático , Temperatura , Transfecção
13.
Am J Physiol ; 277(6): H2381-91, 1999 12.
Artigo em Inglês | MEDLINE | ID: mdl-10600859

RESUMO

Cultured COS-1 cells, as well as chicken embryonic and neonatal rat cardiac myocytes, were infected with recombinant adenovirus vectors to define limiting factors in the expression and Ca2+ transport function of recombinant sarcoplasmic-endoplasmic reticulum Ca(2+) (SERCA) isoforms. Titration experiments showed that all COS-1 cells and myocytes in culture could be infected by an adenovirus titer of 10 plaque-forming units (pfu) per seeded cell. Raising the adenovirus titer further yielded higher protein expression up to an asymptotic limit for functional, membrane-bound SERCA protein. The asymptotic behavior of SERCA expression was not transcription related but was due to posttranscriptional events. The minimal (-268) cardiac troponin T (cTnT) promoter was a convenient size for adenovirus vector construction and manifested tight muscle specificity. However, its efficiency was lower than that of the nonspecific cytomegalovirus (CMV) promoter. At any rate, identical maximal levels of SERCA expression were obtained with the CMV and the cTnT promoter, as long as the viral titer was adjusted to compensate for transcription efficiency. A maximal threefold increase of total SERCA protein expression over the level of the endogenous SERCA of control myocytes was reached (a sevenfold increase compared with the endogenous SERCA of the same infected myocytes due to reduction of endogenous SERCA after infection). In contrast with previous reports [Ji et al. Am. J. Physiol. 276 (Heart Circ. Physiol. 45): H89-H97, 1999], a higher kinetic turnover was demonstrated for the SERCA1 compared with the SERCA2a isoform as shown by a 5.0- versus 2.6-fold increase in calcium uptake rate accompanying maximal expression of recombinant SERCA1 or SERCA2a, respectively. This information is deemed necessary for studies attempting to modify myocardial cell function by manipulation of SERCA expression.


Assuntos
ATPases Transportadoras de Cálcio/genética , ATPases Transportadoras de Cálcio/metabolismo , Miocárdio/enzimologia , Adenoviridae , Animais , Animais Recém-Nascidos , Células COS , Cálcio/metabolismo , Linhagem Celular , Embrião de Galinha , Citomegalovirus/genética , Vetores Genéticos , Humanos , Cinética , Miocárdio/citologia , Regiões Promotoras Genéticas , Ratos , Proteínas Recombinantes/metabolismo , Mapeamento por Restrição , Retículo Sarcoplasmático/enzimologia , Transfecção , Troponina T/genética
14.
J Biol Chem ; 273(24): 15104-9, 1998 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-9614121

RESUMO

Single mutations of specific amino acids within the membrane-bound region of the sarco-endoplasmic reticulum Ca2+ (SERCA)-1 ATPase interfere with Ca2+ inhibition of ATPase phosphorylation by Pi (1), suggesting that these residues may be involved in complexation of two Ca2+ that are known to bind to the enzyme. However, direct measurements of Ca2+ binding in the absence of ATP have been limited by the low quantities of available mutant protein. We have improved the transfection efficiency by means of recombinant adenovirus vectors, yielding sufficient expression of wild type and mutant SERCA-1 ATPase for measurements of Ca2+ binding to the microsomal fraction of the transfected cells. We find that in the presence of 20 microM Ca2+ and in the absence of ATP, the Glu771 --> Gln, Thr799 --> Ala, Asp800 --> Asn, and Glu908 --> Ala mutants exhibit negligible binding, indicating that the oxygen functions of Glu771, Thr799, Asp800, and Glu908 are involved in interactions whose single disruption causes major changes in the highly cooperative "duplex" binding. Total loss of Ca2+ binding is accompanied by loss of Ca2+ inhibition of the Pi reaction. We also find that, at pH 7.0, the Glu309 --> Gln and the Asn796 --> Ala mutants bind approximately half as much Ca2+ as the wild type ATPase and do not interfere with Ca2+ inhibition of the Pi reaction. At pH 6.2, the Glu309 --> Gln mutant does not bind any Ca2+, and its phosphorylation by Pi is not inhibited by Ca2+. On the contrary, the Asn796 --> Ala mutant retains the behavior displayed at pH 7.0. This suggests that in the Glu309 --> Gln mutant, ionization of acidic functions in other amino acids (e.g. Glu771 and Asp800) occurs as the pH is shifted, thereby rendering Ca2+ binding possible. In the Asn796 --> Ala mutant, on the other hand, the Glu309 carboxylic function allows binding of inhibitory Ca2+ even at pH 6.2. In all cases mutational interference with the inhibition of the Pi reaction by Ca2+ can be overcome by raising the Ca2+ concentration to the mM range, consistent with a general effect of mutations on the affinity of the ATPase for Ca2+.


Assuntos
Adenoviridae/genética , ATPases Transportadoras de Cálcio/genética , Cálcio/metabolismo , Retículo Endoplasmático/enzimologia , Retículo Sarcoplasmático/enzimologia , Trifosfato de Adenosina/metabolismo , Animais , Células COS , Proteínas de Ligação ao Cálcio/genética , ATPases Transportadoras de Cálcio/antagonistas & inibidores , Técnicas de Transferência de Genes , Vetores Genéticos/genética , Concentração de Íons de Hidrogênio , Microscopia de Fluorescência , Microssomos/enzimologia , Mutação/genética , Fosforilação , Ligação Proteica/genética , Transfecção/genética
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