Distribution of beta 2-like adrenergic receptors in the cnidarian Renilla koellikeri as revealed by autoradiography and in situ hybridization.

Autoradiography and in situ hybridization were used to examine the histological distribution of the previously characterized beta 2-like adrenergic receptors involved in the bioluminescent activity of the sea pansy Renilla koellikeri. The use of [3H]-(+/-)CGP12177 as radioligand revealed autoradiographic labelling of the refringent granule-filled endoderm at the base of autozooid tentacles and autozooid columns, and in the corresponding endoderm of siphonozooid polyps, all areas where photocytes are concentrated. The presence of excess (10 microM) unlabelled (+/-)CGP12177 or atenolol in the incubation mixture substantially reduced total [3H]-(+/-)CGP12177 labelling. Under low stringency hybridization washing, human beta 2-adrenoceptor oligonucleotide probe signals were detected in granular cells located in those areas of polyp endoderm that were labelled by [3H]-(+/-)CGP12177. These cells were previously shown to be distinct from, but in close proximity to photocytes. No other cell or tissue type was labelled in polyps or throughout colonial tissues. The results suggest that a conserved form of beta 2-adrenergic receptors is present and synthesized in a unique type of endodermal cell indirectly involved in sea pansy bioluminescence control.