Cross inhibition models for the transmission of hormonal signals.

Implications of a model where the formation of two mediators interacting through cross inhibition is stimulated by the same hormone or by two specific hormones are analyzed at steady'state, first in the case where no co-operative processes are involved, secondly in the case where one of the inhibitory branches presents positive co-operativity characteristics. The possible occurrence of agonist concentration-mediators response curves with extrema of opposite type, multiple steady states, hysteresis and discontinuous transitions from one functional program to another is demonstrated. When steady-state hormonal levels fluctuate, it is shown that the cross inhibitory mediators may induce a strict temporal organization of the intracellular processes and result in both amplification and frequency multiplication of the fluctuations.