In babies ranging in age from 1 to 25 weeks and in children between 1 and 14 years, plasma renin activity and urinary aldosterone activity were determined in relation to urinary sodium excretion. A reciprocal correlation was found demonstrating that the hyperactivity of the renin-angiotensin-aldosterone system is stimulated in infants by a low sodium intake. A second stimulus was observed in the influence of the hypothalamo-neurohypophyseal system, when the plasma renin activity was suppressed by administration of antidiuretic hormone and sodium excretion increased due to a decreased aldosterone activity. Our study suggests that there exists a feedback between the renin-angiotensin-aldosterone system and ADH release and that this feedback plays an important role in the regulation of water and electrolyte balance in the young infant.
SummaryIn 16 anesthetized piglets, the effects of I-deamino-8-D-arginine-vasopressin (DDAVP) upon urinary flow rate, relative urinary osrilolarity (U/P,,,,,,I), fractional water excretion (U/Pl,), fractional urca excretion (U/P,,,.,,/U/PI,), renal adenosine 3',5'-cyclic nlonophosphate (c-AMP) formation rate, and medullary c-AMP content were studied during the first 6 days of life. Glomerular filtration rate (GFR) was 0.19 + 0.09 ml/min/g kidney wt (means + SD) on day 1 and increased to 0.51 + 0.11 ml/min/g kidney wt on day 6. It was not affected by the application of 20 pg DDAVP/ kg body wt. On day 1, U/P,,,,,1(1.81 + 0.29), urinary flow rate (5.36 + 1.49 pl/n~in/g kidney wt), U/PI, (31.67 + 6.10) and U/ P,,,.,,/U/PI, (0.84 + 0.12) were not affected by DDAVP application. Fro111 day 2 onward, the reponse of these variables to application of DDAVP increased progressively. On day 6, the following responses were observed: Urinary flow rate decreased from 13.85 f. 7.02 pl/nlin/g kidney wt before DDAVP to 5.07 ? 2.19 pl/min/ g kidney wt after DDAVP. U/P,,,,I raised from 1.24 + 0.27 before DDAVP to 2.64 ? 0.17 after DDAVP. U/PI, increased fro111 36.85 + 13.11 before DDAVP to 109.39 + 22.00 after DDAVP. U/P,,,,,/U/P,, decreased from 0.75 ? 0.05 before DDAVP to 0.55 + 0.04 after DDAVP. These data indicate that the snlall solute permeability of the medullary collecting ducts becon~es increasingly sensitive to antidiuretic hormone (ADII) during this period. The increase in responsiveness of the urinary concentrating system with age was paralleled by the effect of DDAVP on renal c-AMP fornlation rate. In the diuretic control state, no correlation between renal c-AMP fornlation rate and the number of days was observed. llowever, after the application of DDAVP, the nephrogenic fraction of renal c-AMP excretion rate increased from 10.58 + 4.49 pnlole/min/g kidney wt on day 1 to 21.61 + 8.10 pmole/ n~in/g kidney wt on day 6. Similar results were observed with the nledullary c-AMP content. In diuretic control animals which had riot received DDAVP, the medullary c-AMP content ranged between 636 ? 257 pnlole/g wet wt on day 1 and 622 + 75 pmole/g wet wt on day 6. IIowever, in animals which had been infused with DDAVP, niedullary c-AMP content increased from 684 + 274 pnrole/g wet wt on day 1 to 1536 ? 316 pmole/g wet wt on day 6. SpeculationThe unresponsiveness of the medullary adenylatecyclase to AD11 in the newborn kidney might restrict, in addition to other parameters, the renal concentrating ability during the neonatal period.It is generally acknowledged that the concentrating ability of the newborn kidney is reduced in comparison to that of the mature kidney. In the past, this phenomenon was predominately attributed to the structural immaturity of the renal medulla (2, 22), to the reduced G F R and to the anabolic state of the neonatal metabolism, which together result in low filtration-, reabsorption-, and excretion rate of urea (5, 6). It was argued that in spite of the effects of ADH on the permeability of the collecting d...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.