The production and storage of Nerve Growth Factor in vivo by tissues of the mouse, rat, guinea pig, hamster, and gerbil

The Nerve Growth Factor (NGF) content in vivo of tissues from the mouse and rat at various stages of development from 3 days embryonic gestation to the attainment of full maturity has been determined using the standard biological assay. A less extensive survey has also been made of tissues from the guinea pig, hamster, and gerbil. With the exception of the well-documented high levels of NGF in the mouse submaxillary glands, none of the organs examined contained detectable NGF. These results, which are consistent with those previously reported using the biological assay, stand in contrast to the high levels of NGF detected in virtually all tissues by some published radioimmunoassays. It is likely that the discrepancies are due to the use in the radioimmunoassays of antisera containing antibodies to proteins other than NGF, and to the inability of one-site radioimmunoassays to distinguish between the presence of NGF and that of agents capable of binding NGF. The apparent lack of widespread NGF production in vivo contrasts with the ability of many tissues to synthesize the protein in vitro. This may imply that physiologically significant levels of NGF are below the limits of sensitivity of the assay systems presently available, that NGF synthesis in vivo occurs only during a very restricted period of development, or that the presence of a normal innervation pattern influences NGF production.