Effects of calcium ion channel blockers on hamster spermatozoa and oocytes in in vivo and in vitro fertilization

Author(s)

Sandra Helena Gabaldi

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2004-07-14

Examining board members

Cesar Roberto Esper; Valquiria Hyppolito Barnabe; Joaquim Mansano Garcia; Claudia Lima Verde Leal; Maria Angélica Miglino

• Advisor: Cesar Roberto Esper

Abstract

Fertilization process is closely related with calcium ion. There are reports about voltage-dependent calcium ion channel blockers of anti-hypertension therapeutic use causing male infertility, but there are few reports about such effects on the oocyte. The main goal of this experiment was to check the influence of verapamil, nifedipine and diltiazem (L-type voltage-dependent calcium ion channel blockers) on spermatozoa and oocytes. Male and female hamsters were used for in vivo and in vitro experiment. In vitro treatments were preformed in the Experiment I, in which: spermatozoa were capacitated in three concentrations of the three calcium ion channel blockers and they were evaluated for sperm capacitation, hyperactivity and in vitro fertility. Oocytes were incubated for 30 minutes in four concentrations of the same calcium channel antagonists and submitted to in vitro fertilization and evaluation of cortical granules exocytosis. In the Experiment II, calcium channel blockers were supplied twice per day to males during 60 days and to females during 30 days. After this period, drug effects on the animals were evaluated through in vivo fertility, sperm capacitation and hyperactivity, in vitro fertilization, cortical granules exocytosis and transmission electronic microscopy of in vivo treated oocytes. In the Experiment III, the intracellular calcium concentrations were measured in spermatozoa and oocytes in the presence of calcium ion channel blockers. As results, in the Experiment I, the antagonists presented dose-dependent effects, affecting sperm capacitation rate, hyperactivity and in vitro fertilization rate on treated spermatozoa. Treated oocytes presented lower in vitro fertilization rate when compared to the control group and, in the verapamil and diltiazem groups, cortical granules exocytosis was partial and oocyte activation was not concluded. Experiment II showed that male hamsters of treatment groups presented lower sperm capacitation rate, hyperactivity and in vitro fertilization rate and there were fewer pregnant females, demonstrating a reducing male fertility in verapamil and nifedipine groups when compared to the control and diltiazem groups. In vivo fertility of treated females did not change among groups; however, in vitro fertilization rates in oocytes of calcium antagonists in vivo treated females were lower. Nor cortical granules exocytosis neither electronic microscopy detected differences among groups. Progeny of females that received the therapy in the beginning of pregnancy presented lower birth weight and higher mortality rate. In the Experiment III, the antagonists blocked extracellular calcium influx in spermatozoa and in oocytes. It is concluded that, there were calcium ion channels with sensibility to L-type voltage-dependent calcium ion channel blockers in the plasmatic membrane of spermatozoa and oocytes. In in vitro treatments, these antagonists influenced negatively spermatozoa and oocytes capacity of fertilization. Calcium channel blocker therapy reduced the fertility in males, but not in females. Calcium channel blockers supplied in the beginning pregnancy caused teratogenic effects (AU)