[Acute hypocapnia attenuates phosphaturic effect of atrial natriuretic peptide in rats].

This study evaluated phosphate excretion in response to atrial natriuretic peptide during acute hypocapnia in the presence or absence of the renal nerves in rats. To achieve a hypocapnic state, rats were mechanically hyperventilated with room air. As mechanical ventilation per se has been reported to affect renal excretory functions depending on the ventilatory conditions, this study was designed to examine renal functions during acute hypocapnia as compared with those during normocapnia produced by normal and/or hyperventilation. Rats were divided into three experimental groups: 1) a normally ventilated normocapnic (control) group (n = 8), 2) a hyperventilated normocapnic group (n = 8), and 3) a hyperventilated hypocapnic group (n = 8). The innervated right kidney served as a control for the contralateral denervated kidney. Acute renal denervation produced a greater phosphaturia compared to the innervated kidney during the control period in the two normocanic groups but not in the hypocapnic group. Infusion of ANP 12 micrograms/kg/h produced a remarkable increase in phosphate excretion in either kidney in the normocapnic groups. The degree of the phosphaturia (delta FEPi%) during infusion of ANP was similar between the normally ventilated and hyperventilated normocapnic groups both in innervated (10.6 +/- 2.4% and 7.4 +/- 1.2%) and denervated (14.0 +/- 3.0% and 13.5 +/- 2.2%) kidneys. In contrast to both normocapnic groups, the hypocapnic group had a greater hypophosphaturia during the control and ANP infusion periods in either kidney. The increase in fractional excretion of phosphate was smaller both in innervated (0.34 +/- 0.34% delta FEPi) and denervated (0.72 +/- 0.69% delta FEPi) kidneys than that in the other two normocapnic groups.(ABSTRACT TRUNCATED AT 250 WORDS)