AGE-RELATED-CHANGES IN ANGIOTENSIN II-STIMULATED VASCULAR CONTRACTIONAND INOSITOL PHOSPHATE ACCUMULATION IN FISCHER-344 RATS

This study examined the influence of age on angiotensin II (AII)-stimu lated vascular contractile responses and inositol phosphate (IP) accum ulation in Fischer 344 rats. In the aorta, AII-stimulated contraction and IP accumulation were markedly reduced in 6- and 24-month-old rats compared to 1-month-old rats. There was not a significant difference i n the contractile response to AII between 6- and 24-month-old rats, al though IP hydrolysis showed a further decrease between 6 and 24 months . In tail artery, there were no differences in contraction and phospho inositol metabolism in response to AII in the different ages. Losartan blocked AII-stimulated vascular contraction and IP hydrolysis in both aorta and tail artery while PD123319 did not inhibit either response. These data indicate that during maturation, there is a decline in AII -stimulated aortic contraction and IP accumulation in aorta but not in tail artery and these changes are due to altered ATI receptor functio n.