Distribution of G alpha subunit mRNA in rat adrenal cortex and adrenal medulla

Abstract

Mineralocorticoid release from adrenal cortex and catecholamine release from adrenal medulla contribute to the regulation of blood pressure. Release is controlled by actions of several G protein coupled receptors (GPCRs) including angiotensin and melanocortin receptors in the cortex and PACAP and opioid receptors in the medulla. Activation of a GPCR releases the Gá subunit (11 types) that activates downstream signaling components. Stimulatory Gás and inhibitory Gái/o/z subunits act via the cAMP signaling pathway. The aim of this study was to assess distribution of stimulatory and inhibitory Gá subunits in adrenal cortex and medulla to determine the primary signaling pathways utilized. The relative amount of Gá subunit mRNA was calculated in adrenal cortex and adrenal medulla of Wistar Kyoto rats (n=5) using quantitative RT‐PCR. All Gá subunits tested were detected in the cortex and medulla, with a greater abundance of each in the medulla. Abundance was normalized relative to Gz (least abundant subunit) as follows: Gs>Gi2>Gi3>Gi1>Go>Gz in cortex and Gs>>Gi2>Gi3>Go>Gi1>Gz in medulla. Gs and Gi2 were most abundant in both cortex and medulla, suggesting they are the primary stimulatory and inhibitory subunits involved in GPCR‐mediated signaling in adrenal glands. In situ hybrization is currently underway to examine distribution of these subunits in adrenal glands from normotensive and hypertensive animals.