IMMUNOHISTOCHEMICAL LOCALIZATION OF ALPHA(1B)-ADRENERGIC RECEPTORS INTHE RAT IRIS

Expression of the alpha(1B)-adrenergic receptor was investigated immun ohistochemically in the rat iris, cornea and superior cervical ganglio n by using antibodies raised in chickens immunised with a peptide corr esponding to a portion of the 3rd intracellular loop common to the hum an, hamster and rat alpha(1B)-adrenergic receptor. Antibodies stained COS and HEK cell membranes of cells transfected with DNA encoding and expressing the hamster alpha(1B)-adrenergic receptor but not membranes from cells transfected with DNA encoding and expressing the rat alpha (1A)-adrenergic receptor or the rat alpha(1D)-adrenergic receptor. Sta ining was abolished by preincubation of the antibodies with the peptid e used for immunisation, The distribution of alpha(1B)-adrenergic rece ptor was examined immunohistochemically with this antibody (1BI3) and a previously characterised antibody (Ab506) raised in rabbits against the carboxyl-terminal decapeptide of the receptor. In the iris, alpha( 1B)-adrenergic receptor was detected in the dilator muscle, ciliary pr ocesses and posterior epithelium but no staining was observed in the s uperior cervical ganglion with either antibody. By contrast, differenc es in tissue staining between 1BI3 and Ab506 were observed for the sph incter muscle of the iris and for the cornea. 1BI3 stained both tissue s intensely, whereas Ab506 only stained the cornea weakly and the sphi ncter not at all. Reverse transcription/polymerase chain reaction and nucleotide sequencing confirmed the presence of mRNA encoding the epit opes recognised by 1BI3 and Ab506 in cornea and other tissues. We conc lude that (1) there is a good correlation between alpha(1B)-adrenergic receptor mRNA and protein expression in the iris, (2) mRNA, but not p rotein, is detected in the superior cervical ganglion and (3) addition al processes may regulate receptor expression in the cornea.