Effect of Antidiuretic Hormone Upon Urinary Concentrating Ability and Medullary c-AMP Formation in Neonatal Piglets

Abstract

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...

Renal Tubular Development

“…There is some discrepancy about the extent of cAMP production during postnatal maturation in comparison to adults. The balance of data supports that conclusion; although vasopressin stimulates cAMP production in the neonate, the amount of cAMP generated is less than that of the adult [307,[309][310][311].…”

Effect of Haemorrhage on Plasma Lysine Vasopressin and the Cardiovascular Responses to Vasopressin in the Pig Fetus

“…When administered to piglets during the perinatal period it too 10-2 appears to have a relatively restricted antidiuretic activity (Stanier, 1972;Joppich, Kiemann, Mayer & Haberle, 1979;Alt, Colenbrander, Forsling & Macdonald, 1982). Nevertheless, the fetal pituitary contains measurable amounts of vasopressor activity during the second half of gestation (Perks & Vizsolyi, 1973), and interruption of the placental circulation by cord clamping increases plasma concentrations of the hormone in near term fetuses .…”