| Popis: |
Before birth, the ability of the organism to conserve salt and water is not critical as the placenta controls fluid balance in the fetus. The event of birth prompts abrupt changes in the infant's environment, rendering the newborn responsible for maintaining fluid and electrolyte homeostasis. Although nephrogenesis in full-term human infants is completed before birth, tubular development continues during the first few years of life, limiting the kidney's ability to regulate sodium and water excretion. The renal response to arginine vasopressin (AVP) and atrial natriuretic peptide (ANP), two hormones with a major role in sodium and excretion, is developmentally regulated. Although infants have the ability to secrete AVP in response to various stimuli, the response of the immature collecting duct is significantly attenuated. Conversely, circulating ANP levels are decreased in immature mammals due to enhanced clearance. We discuss the developmental regulation of these hormones and potential clinical consequences during the neonatal period. |
