Rat meningeal fibroblasts in primary culture express the proenkephalin gene.

When brought into primary culture, rat meningeal fibroblasts contained proenkephalin-mRNA detected with Northern blot hybridization. In contrast, splenic fibroblasts did not express the gene under the same culture conditions. In situ hybridization showed that the meningeal fibroblasts did not uniformly express the gene: groups of positive cells were surrounded by cells with low or no proenkephalin-mRNA. Some fibroblasts which contained the mRNA species took up bromo-deoxyuridine indicating that the expression of the gene also occurred in proliferating cells, but was not restricted to this group. In chromaffin and astroglial cells, activation of protein kinase A or C with 8 Br.cAMP or O-tetradecanoyl 13-phorbolacetate, respectively, increases the expression of the gene. In meningeal fibroblasts, however, both agents reduced the levels of proenkephalin-mRNA. In the case of 8Br.cAMP, this effect was blocked by the protein synthesis inhibitor cycloheximide indicating that a newly-synthesized protein was involved. Cultured meningeal fibroblasts appear to be useful for studies on the cell specificity of the expression of this peptide gene as well on its regulation.