Expression and Characterization of the Bovine Histamine H₁ Receptor in cDNA-Transfected C6 Astroglioma Cells

Abstract

Rat C6 astroglioma cells (C6-bH₁R cells) expressing cloned bovine histamine H₁ receptors were established by transfection with a vector (pEF-BOS-bH₁R) which carried a 2.7-kbp EcoRI fragment of the bovine H₁ receptor cDNA [Yamashita, M. et al. (1991) Proc. Natl. Acad. Sci. USA 88, 11515-11519]. The cloned bovine H₁ receptor in C6-bH₁R cells was characterized by three established criteria: the [³H]mepyramine binding assay, the accumulation of inositol phosphates induced by histamine, and histamine-induced elevation of intracellular Ca²⁺ concentration, ([Ca²⁺]₁). The accumulation of inositol phosphates induced by histamine was time- and dose-dependent. The accumulation of inositol trisphosphate was biphasic with a prompt increase to the maximal level, followed by a sustained submaximal level. The histamine-induced accumulation of inositol phosphates was suppressed by phorbol ester, but not by pertussis toxin. Results from the [³H]-mepyramine binding assay and histamine-induced elevation of [Ca²⁺]₁ were characteristic of H₁ receptors. Several compounds among tricyclic antidepressants, neuroleptics, and serotonin antagonists showed affinities to the cloned bovine H₁ receptor with K₁ values similar to reported values. Histamine neither induced cAMP accumulation nor attenuated forskolin-induced cAMP accumulation in C6-bH₁R cells. C6-bH₁R cells are particularly useful for studying the H₁ receptor-mediated astroglial cell functions.