Detection and bioimaging of nitric oxide in bovine oocytes and sperm cells

Mammalian gametes contain constitutive nitric oxide synthases (NOS) to synthesize nitric oxide (NO). The detection and bioimaging of NO in bovine gametes is important to determine the regulatory roles of NO during the different events of fertilization. Diaminofluoresceins, new fluorescence indicators for NO, were applied to detect the release of NO from bovine gametes. These compounds yield green fluorescent triazolofluoresceins, which provide the advantages of high specificity, sensitivity, and simplicity for the detection of NO. In this study, we mapped the expression of NOS in the bovine sperm and ova. NOS activity in sperm first appeared in the acrosome, then 60 min later in the head, middle piece, cytoplasmic droplet, and tail. Cow ova had high NO activity in the cytoplasm and in the surrounding corona cells, but not in the zona pellucida. These results show that for bovine gametes, the synthesis NO by the NOS system presents clear patterns of time and spatial distribution that may be important for the different events of fertilization.