Somatostatin receptor subtype 2 and 5 in human GH-secreting pituitary adenomas: analysis of gene sequence and mRNA expression

The role of somatostatin receptor subtypes 2 and 5 (SSTR2 and SSTR5) in determining the secretory and proliferative phenotype as well as the sensitivity to somatostatin analogue treatment is not clearly established. We quantified the expression of SSTR2 and SSTR5 mRNA using a semiquantitative reverse transcription‐polymerase chain reaction (RT‐PCR) in 19 human growth hormone (GH) ‐secreting adenomas. Tumour characteristics and in vivo sensitivity to somatostatin analogues were assessed; tumours were screened for Gsα gene mutations. PCR products of SSTR2 and SSTR5 DNA from tumours resistant to somatostatin analogues were directly sequenced. All tumours expressed both SSTR2 and SSTR5 mRNA at variable levels. No significant correlation between SSTR2 and SSTR5 expression and the presence of Gsα mutation, GH levels, or tumour size and invasiveness was observed. A negative correlation between SSTR2 and SSTR5 mRNA levels was observed (r = 0·5; P