Serum and thyroid hormones T3 and T4 regulate nerve growth factor mRNA levels in mouse L cells

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Abstract
Mouse L cells synthesize and secrete a neurotrophic factor related to the β subunit of the submaxillary gland nerve growth factor (NGF) of male mice. Use of a cDNA probe which encodes the β-NGF mRNA demonstrated that L cells produce a transcript identical in size to that of the submaxillary gland. Moreover, target sites of restriction enzymes EcoRI, PstI and BamHI were not significantly rearranged in the β-NGF gene locus of these cells. The abundance of the β-NGF transcript was found to depend on culture conditions. Removal of serum depressed the cellular content of polyadenylated RNA by a factor of 1.7, and decreased specifically the pool of β-NGF transcript by an additional factor of 4. The presence of 10−7 M testosterone in the serum-free medium did not modify the level of β-NGF mRNA, while addition of 10−7 M T3 (or T4) increased this level by a factor of 1.5. These data provide the first evidence that the β-NGF mRNA of L cells is subjected to regulation, but in a way apparently different from that described for the submaxillary gland.