Abstract
An acute response of LH to a stimulatory pulse of
GnRH is modelled as a result of a pathway (Pathway I) that
consists of two compartments including a single (rate limiting)
intermediate. In addition, a second pathway (Pathway II) was
added, consisting of an intermediate transcription factor and
subsequently a synthesised protein. Pathway II had a delayed
effect on LH release due to the time taken to produce the
intermediate protein. The model included synergism between
these two pathways, which yielded an augmented response.
The model accounts for a number of observations, including
GnRH self-priming and the biphasic pattern of LH response.
The same model was used to fit the data of the LH response
when gonadotrophs responded to the addition of oxytocin in the
response with a shoulder on the profile. Pathway I is able to be
conceptualised as the basic Ca
2+
-mediated pathway. Pathway II
contains features characteristic of the cAMP-mediated pathway.
Thus, we have provided an explanation for details of the nature of
the profile of LH secretion and additionally enabled incorporation
of cAMP in an integrating model. The study investigated the
possibility of two interacting pathways being at the basis of both
the shoulder on the LH surges and self-priming, and the model
illustrates that this appears to be highly likely.