Pressure inhibition of starfish oocyte maturation: Temporal aspects

Abstract

AbstractHigh hydrostatic pressure reversibly inhibits 1‐methylade‐nine (1‐MA)‐induced maturation of starfish oocytes; the objective of this investigation was to describe more fully the nature of this inhibition. Oocytes incubated at atmospheric pressure following a 90‐min period with 1‐MA at high pressure and the removal of exogenous 1‐MA immediately after the reduction in pressure failed to mature. Furthermore, the time required for germinal vesicle breakdown at atmospheric pressure in oocytes preincubated with 1‐MA for 15 min at high pressure was not less than the time required for untreated control oocytes. From a comparison of the percentage of oocytes that matured when incubated at atmospheric or elevated pressure with or without ammonium (20 mM), an inhibitor of 1‐MA that appears to act during an initial step of the hormone dependent period, it was found that the inhibitory action of pressure and ammonium was additive. Inhibition of oocyte maturation was reversible even after 20 hr of incubation at high pressure, but the percentage of oocytes that matured when subsequently incubated at atmospheric pressure was reduced in those oocytes incubated at the elevated pressure with 1‐MA. Taken together, these results suggest that high pressure, like ammonium, inhibits an initial step in the maturational process and that oocytes incubated with 1‐MA at high pressure have a reduced responsiveness to 1‐MA when subsequently incubated at atmospheric pressure.