Identification of alpha 1-adrenergic receptor subtypes in human corpus cavernosum tissue and in cultured trabecular smooth muscle cells.

Abstract

Recent pharmacological and functional studies have suggested the presence of more than one alpha-1 adrenergic receptor subtype in human corpus cavernosum (HCC). In this study, we sought to identify the alpha-1 adrenergic receptor (alpha 1-AR) subtypes expressed in HCC whole tissue and in trabecular smooth muscle subcultured from this tissue. We have utilized RNase protection assays and in situ hybridization (ISH) techniques to identify and localize these receptor subtypes. RNase protection assays of mRNA isolated from whole tissue demonstrated the presence of mRNA transcripts for three alpha 1-AR receptor subtypes (alpha 1d, alpha 1b, and alpha 1a). alpha 1d-AR and alpha 1a-AR appear to be more abundant than alpha 1b-AR. The identification and localization of mRNA for alpha 1-AR subtypes in whole tissue was demonstrated by RNA protection assays and ISH analysis. Immunocytochemical analysis of alpha 1-AR by an antipeptide antibody developed against a specific amino acid sequence derived from alpha 1d-AR subtype demonstrated specific staining of the smooth muscle cells, suggesting the expression of alpha 1d-AR subtype. In cultured HCC smooth muscle cells (HCC SMC), phenylephrine,alpha 1-AR agonist stimulated Na+/K+ ATPase activity, suggesting the presence of functional alpha 1-AR. RNase protection assay of mRNA isolated from HCC SMC grown in culture further demonstrated the presence of mRNA transcripts for alpha 1d-AR and alpha 1a-AR subtypes. ISH analysis and confocal microscopy also indicate that the SMC express the alpha 1d-AR and alpha 1a-AR subtypes. The data presented suggests that HCC and SMC derived from this tissue express at least three alpha 1-AR subtypes. Identification of these receptor subtypes should allow characterization of the functional role of these receptor subtypes in regulation of trabecular smooth muscle tone and penile detumescence.