Urinary cyclic AMP and renal concentrating capacity in infants
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Infant kidneys respond to antidiuretic hormone (ADH), with its effects mediated by cyclic AMP (cAMP). This study shows ADH enhances kidney concentrating ability in infants, crucial for development.
Area of Science:
- Pediatric Nephrology
- Endocrinology
- Molecular Biology
Background:
- The renal concentrating capacity in infants is not fully mature.
- Antidiuretic hormone (ADH) plays a key role in regulating water balance and urine concentration.
- The role of ADH and cyclic AMP (cAMP) in infant kidney function requires further elucidation.
Purpose of the Study:
- To investigate the effect of exogenous antidiuretic hormone (ADH) on renal concentrating capacity and urinary cyclic AMP (cAMP) in infants.
- To explore the relationship between age, urinary osmolality, urea, and cAMP excretion in normally hydrated infants.
- To understand the maturation of the infant kidney's concentrating ability and its correlation with the cAMP system's responsiveness to ADH.
Main Methods:
- Administered exogenous antidiuretic hormone (ADH) to 15 infants (1-31 weeks old) and measured urine flow, osmolality, urea, and cyclic AMP (cAMP).
- Analyzed urine samples from 52 normally hydrated infants to assess age-related changes in osmolality, urea, and cAMP excretion.
Main Results:
- Exogenous ADH significantly decreased urine flow and increased urine osmolality, urea, and cAMP in infants, indicating distal nephron responsiveness mediated by cAMP.
- A nonlinear, age-related increase in urinary osmolality and urea was observed in infants, paralleled by a similar pattern in cAMP excretion.
- These findings suggest that the maturation of renal concentrating capacity in infants is linked to enhanced cAMP system responsiveness to ADH.
Conclusions:
- The infant kidney's distal nephron is responsive to ADH, with its action mediated by the cAMP second messenger system.
- The maturation of renal concentrating ability in infants appears to be associated with an increasing responsiveness of the cAMP system to ADH.
- Elevated urea and solute concentrations in the infant kidney medulla/papilla may additionally stimulate cAMP formation, particularly with low endogenous ADH secretion.
Abstract:
In 15 infants between 1 and 31 weeks the effect of antidiuretic hormone (ADH) on the renal concentrating capacity and urinary cyclic AMP (cAMP) was tested. A significant decrease of urine flow and a significant increase of osmolality, urea and cAMP was observed indicating that the distal nephron of the infant kidney is responsive to exogenous ADH and that its effect is mediated by cAMP. The results of a second series with 52 normally hydrated infants demonstrate that the nonlinear age-related increase of osmolality and urea in urine is accompanied by a similar pattern of cAMP excretion, pointing out that the maturation of the concentrating capacity seems to be related to an increasing responsiveness of the cAMP system to ADH. Furthermore the results raise the possibility that increasing concentrations of urea and solutes in the medulla and papilla of the infant kidney may have--in the presence of very low ADH secretion--an additional stimulating effect on cAMP formation.