Calcium concentration and fertilization by subzonal insemination of a single spermatozoon in mouse oocytes

Abstract

The effect of calcium concentration in culture medium on the fertilization of subzonally microinseminated mouse oocytes was examined. Oocytes were injected with a single spermatozoon so that the sperm head was forced to adhere onto the ooplasmic membrane with a micromanipulation technique. For the inseminations, epididymal spermatozoa preincubated in culture medium and those treated with ionophore A23187 were used. Inseminated oocytes were cultured using media with three different calcium concentrations of 1.71, 3.42, and 5.13 mM; 40.0%, 71.6%, and 47.9% of oocytes microinjected with preincubated sperm were fertilized after incubation with those media, respectively. When the oocytes inseminated with ionophore-treated sperm were incubated in media containing 1.71 and 3.42 mM calcium, their fertilization rates were 58.2% and 87.5%. Thus fertility of subzonally microinseminated oocytes was obviously enhanced when cultured in medium with 3.42 mM of calcium, irrespective of being inseminated with preincubated sperm (P < 0.01) or with ionophore-treated sperm (P < 0.005). Some of the microinseminations with preincubated sperm were performed without sperm adhered to the oolemma. In these cases, the incidence of fertilization was not improved by incubating the inseminated oocytes in medium containing 3.42 mM calcium (32.6%) as compared to those incubated in medium with 1.71 mM calcium (28.3%). These results suggest that the concentration of extracelluar calcium exerts an important effect on the progress of fertilization events subsequent to sperm adherence onto the ooplasmic membrane. Almost 80% of the zygotes fertilized via incubation in medium with 3.42 mM of calcium developed into blastocysts after culturing in vitro.

Vitamin D3 receptor is expressed in the endometrium of cycling mice throughout the estrous cycle

“…As demonstrated in our data, the expression of VDR in the epithelial cells of the fallopian tubes might serve a role in the regulation of calcium transport in these cells, similar to the regulatory functions of intestinal epithelial cells in intestinal calcium transport (38,39). It is noteworthy to mention that fertilization of the egg in the fallopian tubes only occurs within a small window of extracellular calcium concentration (40).…”

Vitamin D and reproductive disorders: a comprehensive review with a focus on endometriosis

“…Vitamin D may impact P450 aromatase activity in granulosa cells, essential for the conversion of androstenedione to estradiol [ 57 ]. Vitamin D may regulate calcium transport across the fallopian tube epithelium, which is necessary for successful fertilization in the fallopian tube lumen [ 43 , 58 ].…”