Effect of Aging on Single Nephron Renin Content in Rats

Abstract

To investigate the relation between renin content in each juxtaglomerular apparatus and reduction of plasma renin activity (PRA) with aging, the PRA and microdissected superficial or juxtamedullary single nephron renin content (SNRC) were determined in 5 young (3–6 months) and 5 aged (13–18 months) rats fed on a normal salt diet. The mean value of the PRA in the aged group was significantly lower than that of the young group. A highly significant correlation was found between the RPA and mean values of the superficial SNRC. The mean values of both the superficial and deep SNRC in the aged rats were significantly lower than those of the corresponding zones in the young rats. It is suggested that decreased synthesis of renin in each juxtaglomerular apparatus is an important factor in the decreased PRA observed with aging.

Age-Related Change in Plasma Aldosterone Response to Exogenous Angiotensin II in the Rat

“…Whatever the reason for the reduced aldosterone re sponse of the adrenal cortex to angiotensin II, the present study is the first to strongly suggest that the lower plasma concentration of aldosterone, previously reported in the old rat [ 15] is, at least partly, due to a decrease with age of the aldosterone biosynthesis capacity of the adrenal glo merular cells in response to angiotensin II; a primary con tributing factor being the decrease in plasma renin activi ty with increasing age [16,17],…”

“…Furthermore, the results of Hayashi et al [16] and Corman and Michel [17] indicated that the activity of the renin-angiotensin system was progressively reduced as the animals became older. Among the reasons for the diminished aldosterone secretion with age might be an impaired sensitivity of the adrenal cortex to the main factors involved in the control of aldosterone production and particularly to the most important of them, angiotensin II.…”

Age-Related Changes in Plasma Corticosterone and Aldosterone Responses to Exogenous ACTH in the Rat

“…Although some controversy subsists, a number of in vivo studies have documented an age-related decline in the adrenal secretion of corticosterone [1][2][3] and aldoste rone [4][5][6][7][8], These impairments might be, at least in part, due to a reduced secretion of corticotropin, as reported by some authors [9][10][11], although not by others [12,13] and/ or to a diminished activity of the renin-angiotensin sys tem [5,8,[14][15][16] during aging. A contributing reason may be an altered sensitivity of the adrenal cortex to the main Therefore, in the present study we measured concomi tantly in the same animals both the corticosterone and the aldosterone responses of the adrenal cortex of different age groups of female and male Long-Evans rats to exoge nously administered ACTH (1-24).…”

Age and the Renal Blood Supply: Renal Vascular Responses to Angiotensin Converting Enzyme Inhibition in Healthy Humans

“…Rats resemble humans in displaying an age‐related fall in RBF, glomerular filtration rate, and reduced activity of the renin‐angiotensin system (RAS) 23–27 . This is associated with suppression of the intrarenal RAS, and — unlike the findings in this study — a blunted renal vasodilator response to ACE inhibition 26 .…”