Effect of exogenous DMNPE-caged ATP on in vitro-matured bovine oocytes prior to parthenogenetic activation, fertilisation and nuclear transfer

Adenosine triphosphate ( ATP) plays an important role during fertilisation of the mammalian oocyte through its ability to alter the frequency and duration of calcium oscillations. It has also been shown that higher ATP levels correlate with increased developmental competence in bovine and human oocytes. During somatic cell nuclear transfer ( NT), the incoming nucleus is remodelled extensively, undoubtedly using a variety of ATP-dependent enzymes. The aim of the present study was to determine whether additional exogenous ATP influences activation of parthenogenetic ( PA), in vitro- fertilised ( IVF) or cloned ( NT) in vitro- matured bovine oocytes. Blastocyst development and cell numbers in PA embryos were found to increase in a dose- dependent manner following the photorelease of 0, 50, 100, 500 and 1000 mum DMNPE- caged ATP ( adenosine 5 '- triphosphate, P3-( 1-( 4,5- dimethoxy-2- nitrophenyl) ethyl) ester, disodium salt). No cleavage was found following release of 2 and 5 mm DMNPE- caged ATP or with DMNPE- caged ATP ( not photoreleased). There were also no differences in blastocyst rates or cell numbers between the control group and groups treated with caged, but not photoreleased, ATP. The addition of exogenous ATP before IVF or to NT couplets did not result in a significant increase in blastocyst development or cell number. Embryo transfer is necessary to determine whether exogenous ATP can positively affect reprogramming, resulting in higher cloned pregnancy rates or live- term births.