Angiotensins actions

Renal action. Angiotensin acts on renal function modifying pressure in renal artery and tubular reabsorption of sodium (26,41). Effect on diuresis is variable in different animals. In the rabbit or rat, diuresis and increased excretion of electrolytes are the rule (34, 35). In normal man, intravenous infusion produces an antidiuresis and a reduction in excretion of electrolytes (6, 9). On the contrary, in man with hypertension, angiotensin causes diuresis with natriuresis (8), This difference suggests that in normal man, angiotensin exerts a powerful effect on renal vessels so that the direct tubular action would be masked. 

ACE not only activates angiotensin but is also involved in the metabolism of other peptides, e.g., it is a major kinin-degrading enzyme. Therefore, ACE inhibitors also increase kinin concentrations. Furthermore, it has recently been shown that these drugs potentiate kinin effects by modulating a direct interaction between the ACE protein and the kinin B2 receptor, which is independent from the enzymatic activity of ACE. Kinin potentiation may be involved in the beneficial action of ACE inhibition since kinins are known to exert cardio- and renoprotective actions. 

As is the case with tryptase, chymase is also stored in mast cell granules. This mediator can activate the angiotensin system converting angiotensin I to angiotensin II. With this action it compensates the intravascular loss of volume and the permeability... 

Angiotensin II binds to specific adrenal cortex glomerulosa cell receptors. The hormone-receptor interaction does not activate adenylyl cyclase, and cAMP does not appear to mediate the action of this hormone. The actions of angiotensin II, which are to stimulate the conversion of cholesterol to pregnenolone and of corticosterone to 18-hydroxycorticosterone and aldosterone, may involve changes in the concentration of intracellular calcium and of phospholipid metabolites by mechanisms similar to those described in Chapter 43. 

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