Age-related changes in renal cyclic nucleotides and eicosanoids in response to sodium intake

The signaling molecules cGMP, cAMP, prostaglandin E-2 (PGE(2)), and prostag landin F-2 alpha (PGF(2 alpha)) play important roles in mediating the respo nse of the kidney to changes in dietary sodium intake. We used a renal micr odialysis technique in conscious rats to address the hypothesis that the re nal ability to produce these mediators in response to dietary sodium intake is altered during maturation. Young (4-week-old) or adult (6-month-old) ra ts were studied after the consumption for 5 days of diets containing low (0 .04% NaCl), normal (0.28% NaCl), or high (4.0% NaCl) levels of sodium. Plas ma renin activity was significantly increased by low-sodium diet and signif icantly decreased by high-sodium diet, with no significant difference betwe en the responses of the 2 age groups. Renal interstitial fluid (RIF) levels of cGMP, cAMP, PGE(2), and PGF(2 alpha) on normal-sodium diet were similar in the 2 age groups. Low-sodium diet caused a significant increase in RIF levels of all 4 mediators, with no significant differences between the resp onses of the 2 age groups. High-sodium diet also caused a significant incre ase in RIF levels of all 4 mediators. However, RIF production of cGMP, cAMP , and PGE(2) was significantly greater, and RIF PGF(2 alpha) production was significantly lower, in young rats compared with adult rats. These data de monstrate that the kidneys of young and adult rats respond to dietary sodiu m restriction in a similar manner but that there are age-related changes in the renal response to sodium loading.