The inositol polyphosphate-diacylglycerol-protein kinase C system

The inositol polyphosphate-diacylglycerol-protein kinase C system 

Stimulation of IP3 formation by TRH has also been shown in normal pituitary cells in culture. 

In contrast to TRH, VIP does not seem to increase PIP2 hydrolysis [108], a finding suggesting that Ca2+ mobilization by IP3 is not involved in VIP-stimulated PRL secretion. This is consistent with the notion that cAMP is the messenger for this effect. 

The incorporation of labeled phosphate in PI to generate PIP2 in normal as well as in 7315a PRL-secreting tumor cells appears to be inhibited by DA [109,110]. Whether this effect is related to the hydrolysis of PIP2 into IP3 and consequent Ca2+ mobilization from endoplasmic reticulum remains to be shown. 

There is general agreement that LHRH stimulates the incorporation of labeled phosphate into the phosphoinositides PI, PIP and PIP2 [111-115]. This has also been 

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