Is PAF a local regulator? 10 pts!!?

Question

What is a local regulator in terms of signaling? Which cells secrete PAF and when? THANKS!

Answer 1

In terms of cell signaling a local regulator is a component of the pathway which is locally present within the tissue. Basically, all of the components necessary to elicit a response exist within the tissue itself, and probably do so at some basal level. This contrasts with a response elicited by some some exogenous signal (hormonal, neuronal).

For example PAF is produced in response to specific stimuli (e.g. irritation) by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells. The inflammatory response isn't initiated by the CNS or some endocrine-related signal. All of the components for that signaling pathway are "local", if you will.

Problems may arise, as you can imagine, when something that is local and focused becomes diffuse or systemic. Septic shock is a great example, as lipopolysaccharide fragments can induce production of PAF from vascular endothelium which in turn acts as a vasodilator on that same tissue.