Sequences from cDNA molecules encoding α ₂ -adrenoceptor subtype genes were subcloned into prokaryotic vectors and riboprobes generated to hybridise selectively with each of the human α ₂ C2-, α ₂ C4- and α ₂ C10-adrenoceptor subtype mRNA species. The riboprobes were labelled with either ³² P or digoxigenin and used to study the expression of α ₂ -adrenoceptor subtypes in sections of human pancreas, in isolated human islets of Langerhans and in clonal HIT-T15 pancreatic β-cells. Using a ribonuclease protection assay protocol, expression of mRNA species encoding both α ₂ C2 and α ₂ C10 was demonstrated in preparations of isolated human islets of Langerhans. mRNA encoding α ₂ C4 was also detected in human islet RNA, using reverse transcription coupled with the polymerase chain reaction. In situ hybridisation was then employed to examine the distribution of each α ₂ -adrenoceptor subtype in sections of human pancreas. All three subtypes of α ₂ -adrenoceptor mRNA were identified in sections of formalin-fixed, paraffinembedded human pancreas using riboprobes labelled with digoxigenin. Although some labelling of the three α ₂ -adrenoceptor mRNA subtypes was seen in the islets, the labelling was most intense in the exocrine tissue of the pancreas for each receptor subtype. The specificity of the digoxigenin-labelled RNA probes was confirmed in several control tissues and by in situ hybridisation studies using sense probes in the pancreas. The integrity of the pancreas sections was confirmed by in situ hybridisation with an antisense riboprobe derived from human insulin cDNA. The results demonstrate that multiple α ₂ -adrenoceptor subtypes are expressed in human pancreas. Both the exocrine and endocrine cells express more than one receptor subtype, although the islets stain less intensely than the bulk of the tissue suggesting that the islet cells may have lower levels of expression than the acinar tissue. The presence of α ₂ -adrenoceptor subtype mRNA species in pancreatic β-cells was confirmed by Northern blotting of RNA extracted from the clonal β-cell line, HIT-T15. Transcripts encoding each of the three cloned α ₂ -adrenoceptor subtypes were detected in HIT-T15 cells.

Hybridisation of sections of human pancreas with oligodeoxynucleotide probes designed to hybridise with β ₂ -adrenoceptor mRNA revealed expression of this species in islet β-cells but not in the exocrine tissue of the pancreas.

Journal of Endocrinology (1996) 148, 531–543