IDENTIFICATION OF ALPHA(1)-ADRENERGIC RECEPTOR SUBTYPES IN HUMAN CORPUS CAVERNOSUM TISSUE AND IN CULTURED TRABECULAR SMOOTH-MUSCLE CELLS

Recent pharmacological and functional studies have suggested the prese nce of more than one alpha-1 adrenergic receptor subtype in human corp us cavernosum (HCC). In this study, we sought to identify the alpha-1 adrenergic receptor (alpha(1)-AR) subtypes expressed in HCC whole tiss ue and in trabecular smooth muscle subcultured from this tissue. We ha ve utilized RNase protection assays and in situ hybridization (ISH) te chniques to identify and localize these receptor subtypes. RNase prote ction assays of mRNA isolated from whole tissue demonstrated the prese nce 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 localiza tion of mRNA for alpha(1)-AR subtypes in whole tissue was demonstrated by RNA protection assays and ISH analysis. Immunocytochemical analysi s of alpha(1)-AR by an antipeptide antibody developed against a specif ic amino acid sequence derived from alpha(1d)-AR subtype demonstrated specific staining of the smooth muscle cells, suggesting the expressio n of alpha(1d)-AR subtype. In cultured HCC smooth muscle cells (HCC SM C), phenylephrine, alpha(1)-AR agonist stimulated Na+/K+ ATPase activi ty, suggesting the presence of functional alpha(1)-AR. RNase protectio n assay of mRNA isolated from HCC SMC grown in culture further demonst rated the presence of mRNA transcripts for alpha(1d)-AR and alpha(1a)- AR sub types. ISH analysis and confocal microscopy also indicate that the SMC express the alpha(1d)-AR and alpha(1a)-AR subtypes. The data p resented suggests that HCC and SMC derived from this tissue express at least three alpha(1)-AR subtypes. Identification of these receptor su btypes should allow characterization of the functional role of these r eceptor subtypes in regulation of trabecular smooth muscle tone and pe nile detumescence.