Fluctuation of histone H1 kinase activity during meiotic maturation in porcine oocytes

Porcine oocytes cultured in follicular fluid for various periods of up to 48 h were stained with Hoechst-33342 and classified according to maturation before assaying. Histone H1 kinase activity at metaphase I was approximately 10 times that at the germinal vesicle stage. An abrupt reduction in activity was observed in oocytes emitting the first polar body; then the activity increased again to the same level as at metaphase I. This pattern is similar to those reported in non-mammalian species and supports the concepts that histone H1 kinase is ubiquitous in eukaryotes and controls the meiotic cell cycle in mammals.