Localization of messenger ribonucleic acids for somatostatin receptor subtypes (sstr1-5) in the rat adrenal gland

Somatostatin (somatotropin-release inhibitory factor, SRIF) exerts multiple inhibitory actions throughout the central nervous system and the periphery by binding to specific membrane-bound SRIF receptors (sstrs) of which five subtypes (sstr1-5) have now been identified. Individual sstr subtypes have been suggested to mediate selective biological actions of SRIF. Although the adrenal gland is a known target of SRIF action, the sstr subtypes involved in its actions are unclear. This study examined the expression of sstr1-5 in rat adrenal gland by RT-PCR analysis and in situ hybridization (ISH) histochemistry. Using RT-PCR expression combined with Southern blotting, sstr1, -2, -4, and -5 mRNAs were shown in the adrenal gland. ISH histochemistry revealed strong expression of sstr2 mRNA alone localized to the zona glomerulosa of the adrenal cortex and moderate labeling in scattered cells of the adrenal medulla, indicating a possible role for sstr2 in mediating SRIF physiology in this tissue by altering adrenal aldosterone and catecholamine secretion. These data also point to potential roles for sstr subtypes sstr1, -4, and -5 in the adrenal gland.