GUINEA-PIG HISTAMINE H-1 RECEPTOR .1. GENE CLONING, CHARACTERIZATION, AND TISSUE EXPRESSION REVEALED BY IN-SITU HYBRIDIZATION

An intronless DNA encoding the guinea pig H-1 receptor was cloned from a genomic library using probes derived from the bovine H-1 receptor. It encodes a protein of 488 amino acids with a calculated molecular mass of 55,619 daltons compared with a size of 56-68 kDa for the photoaffinity-labeled receptor as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The protein displays a 66% homology with the bovine receptor. Stable expression of the H-1 receptor, characterized by the appearance of [H-3]mepyramine binding sites with a pharmacology similar to that of the native H-1 receptor, was obtained following transfection of Chinese hamster ovary cells. Southern blot analysis, using a variety of restriction enzymes, did not provide any evidence of multiple H-1 isoreceptors. Northern blot analysis of a variety of guinea pig peripheral or cerebral tissues identified, in most cases, a single transcript of 3.3 kb, but also, in some tissues, a second transcript of 3.7 kb, possibly generated by the use of different promoter or polyadenylation sites or corresponding to a transcript from a distinct gene. In situ hybridization studies showed the highly contrasted cerebral expression of H-1-receptor gene transcripts, which was compared with autoradiographic receptor localization. This allowed the identification of some major cell populations expressing the H-1 receptor, e.g., Purkinje cells in cerebellum or pyramidal cells in the hippocampal complex.