Detection of the messenger RNA coding for preproenkephalin A in bovine adrenal by in situ hybridization

Abstract

The messenger RNA (mRNA) coding for the adrenal precursor of enkephalins (preproenkephalin-A) has been detected in bovine adrenal medulla cells using in situ hybridization with 32P-labelled preproenkephalin A (PPA) complementary DNA. In formaldehyde- and Carnoy-fixed tissue sections, an intense elective labelling restricted to the cells located at the periphery of the adrenal medulla can be detected after hybridization procedure, using X-ray film and classical autoradiographic procedure. Adequate controls show that this labelling is obtained only using PPA complementary DNA, inserted or not in its vector. Distribution of PPA mRNA appears identical to that of its immunoreactive end products, namely Met-enkephalin and BAM22 peptide, detected by immunohistochemistry. Norepinephrine, detectable using monoamine histofluorescence, appears restricted to the cells of the center of the gland unlabelled for PPA mRNA and its end-products. Cultured bovine adrenomedullary cells that exhibited enkephalin immunoreactivity also contain PPA mRNA located in their cytoplasm. These results provide histological evidence for expression of PPA gene in bovine adrenal cells and show the presence of two distinct cell populations in the bovine adrenal medulla, only one of which produces PPA-derived peptides. This work shows that the in situ hybridization procedure using 32P-labelled complementary DNA can be conveniently used to appreciate gene expression in heterocellular tissues such as the adrenal.