ABSTRACT
Angiotensin II (AngII) was originally characterized as an octapeptide hormone with potent pressor activity in the cardiovascular system. In addition to its marked vasoconstrictor actions, AngII is now recognized as a multifunctional regulatory peptide with actions in numerous target tissues, including adrenal, kidney, brain, liver, and gonads. AngII receptors mediate the expression of phenotypic cellular responses to AngII by coupling via guanyl nucleotide regulatory (G)-proteins to plasma membrane effector enzymes and ion channels. Specific binding sites for AngII are present in the adrenal cortex and represent the cell surface receptors through which the peptide stimulates steroidogenesis. In early studies, guanine nucleotides were found to decrease the affinity of AngII for its binding sites, an effect which suggested that AngII receptors are coupled to guanine nucleotide binding proteins. AngII also causes a receptor-mediated increase in protein synthesis in heart cells, as shown by studies in embryonic chick myocytes.
