Mm. Fahy et Mt. Kane, EFFECTS OF LITHIUM-CHLORIDE ON RABBIT BLASTOCYST EXPANSION, AND ACCUMULATION OF PHOSPHOINOSITIDES AND INOSITOL PHOSPHATES, Journal of Reproduction and Fertility, 100(2), 1994, pp. 347-352
The effects of lithium, an inhibitor of the recycling of inositol in t
he phosphatidylinositol cycle, on rabbit blastocyst growth and metabol
ism of phosphoinositides were investigated. Day 2 rabbit morulae were
first cultured for 2 days in basic culture medium and then transferred
to medium containing myo-[2-H-3]inositol for culture for a further 3
days. At the end of culture, the resulting blastocysts were incubated
with LiCl (0, 1, 5, 10, 20 mmol l(-1)) for 1h. The blastocysts were th
en lysed and both the aqueous and lipid portions were analysed for inc
orporated radioactivity. Thin layer chromatographic separation of the
lipid portion indicated that lithium had no significant effect on form
ation of radiolabelled phosphoinositides. However, high performance an
ion exchange chromatography indicated that lithium significantly stimu
lated accumulation of radiolabelled inositol monophosphate and inosito
l 1,4,5-trisphosphate, This result indicates that the phosphatidylinos
itol cycle is turning over in rabbit blastocysts. Continuous culture o
f rabbit embryos for 5 days in media containing LiCl (5, 10, 15 and 20
mmol l(-1)) significantly decreased blastocyst growth as measured by
blastocyst expansion and incorporation of [H-3]thymidine. However, sup
plementing the medium with excess inositol (up to 9375 mu mol l(-1)),
in an attempt to increase the intracellular uptake of inositol and thu
s compensate for the inhibitory effect of lithium on inositol recyclin
g, did not reverse the inhibitory effect of lithium on blastocyst grow
th.