Chapter 11, Problem 16RA

What do insulin-like growth factors, neurotrophins, nitricoxide, and lymphokines have in common?

$\begin{array}{l}\text{a}\text{. They are hormones}\text{.}\hfill \\ \text{b}\text{.}\text{They are autocrine or paracrine regulators}\text{.}\hfill \\ \text{c}\text{.}\text{They are neurotransmitters}\text{.}\hfill \\ \text{d}\text{.}\text{They all use cAMP as a second messenger}\text{.}\hfill \\ \text{e}\text{.}{\text{They all use Ca}}^{\text{2+}}\text{ as a second messenger}\text{.}\hfill \end{array}$