Regenerative and non-regenerative @entity460 transients in hamster eggs triggered by XXXX .

@entity671 @entity329 @entity460 @entity972 @entity141
1. @entity671 (InsP3) injected into unfertilized @entity329 eggs elicits a hyperpolarizing response (HR) that is due to stimulation of @entity460 -activated @entity972 channels in the egg plasma membrane. 2. A single injection of InsP3 gave a single HR above a threshold value of 0.3 nM. At 5 nM and above, InsP3 induced HRs with no detectable latency. At concentrations between these two values a latency was observed. The amplitude of the HR was independent of InsP3 concentration. 3. A second HR could be elicited by injection of InsP3, but five times more InsP3 was required to trigger a second HR, and 10-100 times more to give an HR of similar magnitude to the first, and there was no latency. 4. The increase in [ @entity141 ]i in response to an initial injection of 1 nM InsP3 could be resolved into two distinct components: a slow, early rise immediately after InsP3 injection (phase I) followed by a larger and more rapid increase (phase II). The initiation of an HR coincided with the second component of the [ @entity141 ]i increase. 5. Further injection of InsP3 resulted only in slow, smaller increases in [ @entity141 ]i that resembled phase I and often did not cause an HR. Phase II appeared to be absent. However, 100-fold greater InsP3 concentrations gave slow, larger @entity141 transients (and HRs) with no detectable latency. 6. If large amounts of InsP3 were allowed to leak into the eggs constantly from a pipette, repetitive @entity460 transients were seen. Unlike the sustained repetitive responses seen at fertilization, they were often smaller than the initial transient and less well sustained. However, a subsequent transient could still be elicited on injection of very large concentrations of InsP3. 7. InsP3 can induce regenerative, all-or-none [ @entity141 ]i increase (CICR) in hamster eggs, often with a long latency, as well as non-regenerative increases. InsP3 injections desensitize CICR and cannot mimic all the features of @entity141 signalling at fertilization in the hamster egg, in particular, the sensitization of CICR caused by the sperm.
