EXPRESSION OF MESSENGER-RNA FOR SOMATOSTATIN RECEPTOR (SSTR) TYPE-2 AND TYPE-5 IN INDIVIDUAL, RAT PITUITARY-CELLS - A DOUBLE-LABELING IN-SITU HYBRIDIZATION ANALYSIS

To characterize cell specific expression of sstr subtypes in the pitui tary we have analyzed mRNA for sstr1-5 in rat pituitary somatotrophs b y reverse transcriptase polymerase chain reaction and determined the p attern and level of expression of mRNA for sstr subtypes 2 and 5 in in dividual pituitary cell subpopulations by double label in situ hybridi zation. Purified somatotrophs expressed mRNA for all 5 sstrs. In situ hybridization analysis revealed sstr5 mRNA in 70% of somatotrophs, 57% of thyrotrophs, 38% of corticotrophs, 33% of lactotrophs, and 21% of gonadotrophs. mRNA for sstr2 occurred in 40% of somatotrophs, 36% of t hyrotrophs, 26% of lactotrophs, 3% of corticotrophs, and 8% of gonadot rophs. Not only were more cells positive for sstr5 mRNA but the averag e number of autoradiographic grains/cell was also higher for sstr5 tha n sstr2. These results show expression of multiple sstr genes in indiv idual pituitary cells. mRNA for sstr2 and 5 occur in each of the 5 maj or pituitary cell subsets, sstr5 mRNA being more widely and more abund antly expressed than sstr2.