ABSTRACT
In this chapter, the authors review the molecular characteristics of the AT1B receptor, the tissue distribution of its mRNA, the hormonal regulation of its mRNA expression, the predicted functional differences between AT1B and AT1A receptor proteins, and the evidence that the AT1 receptor subtypes are encoded by separate genes. Angiotensin II receptor radioassays performed on Cos-7 cells transiently transfected with the AT1B cDNA revealed a pattern of ligand displacement similar to that observed in a variety of AngII target tissues including the anterior pituitary gland. The pattern of nucleotide and amino acid sequence differences between AT1 and AT1A receptors is not characteristic of alternatively spliced RNA, suggesting that they are encoded by different genes. The adrenal and anterior pituitary glands and the two circumventricular organs of the brain, subfornical organ, and organum vasculosum of the lamina terminalis, all express primarily AT1B receptor mRNA, whereas vascular smooth muscle cells express primarily AT1A mRNA.
