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 cont rast, splenic fibroblasts did not express the gene under the same cult ure conditions. In situ hybridization showed that the meningeal fibrob lasts did not uniformly express the gene: groups of positive cells wer e surrounded by cells with low or no proenkephalin-mRNA. Some fibrobla sts which contained the mRNA species took up bromo-deoxyuridine indica ting that the expression of the gene also occurred in proliferating ce lls, but was not restricted to this group. In chromaffin and astroglia l cells, activation of protein kinase A or C with 8 Br.cAMP or O-tetra decanoyl 13-phorbolacetate, respectively, increases the expression of the gene. In meningeal fibroblasts, however, both agents reduced the l evels of proenkephalin-mRNA. In the case of 8Br.cAMP, this effect was blocked by the protein synthesis inhibitor cycloheximide indicating th at a newly-synthesized protein was involved. Cultured meningeal fibrob lasts appear to be useful for studies on the cell specificity of the e xpression of this peptide gene as well on its regulation.