Differential gene expression and regulation of type-1 angiotensin II receptor subtypes in the rat

Abstract

A simplified and sensitive method for measuring expression levels of type-1 angiotensin II (AT 1) receptor subtypes, AT 1A and AT 1B, was established. The two receptor cDNAs were co-amplified and measured by polymerase chain reaction using primers based on the corresponding receptor subtype genes. Both AT 1A and AT 1B mRNAs were widely expressed in the rat tissues including adrenal gland, kidney, heart, aorta, lung, liver, testis, pituitary gland, cerebrum and cerebellum. AT 1A mRNA was predominantly expressed in the rat tissues examined except adrenal gland and pituitary gland where AT 1B mRNA was predominantly expressed. Sodium depletion did not change mRNA levels of AT 1A and AT 1B in the all tissues. However, both AT 1A and AT 1B mRNA levels in the heart and aorta were down-regulated by treatment with AT 1 specific antagonist, TCV 116. In contrast, AT 1B mRNA in the adrenal gland was mainly reduced by the treatment. These results suggest that the expression level of AT 1B mRNA in the adrenal gland depends on the activity of the renin-angiotensin-aldosteron system (RAAS) and both receptor subtypes mediate contraction and hypertrophy of the smooth and cardiac muscles via the RAAS.