Neuropeptide Y and blood pressure in haemodialysis patients

To investigate the relationship between plasma neuropeptide Y (NPY) concentrations and blood pressure in haemodialysis (HD), we measured plasma immunoreactive neuropeptide Y (IR-NPY) concentrations and blood pressure before and after HD in 71 patients undergoing maintenance HD. Plasma IR-NPY concentrations were measured by radioimmunoassay after extraction with Sep-Pak C18 cartridges. We corrected the plasma IR-NPY values after HD by reference to the ratio of the plasma total protein levels before HD to the levels after HD, in order to exclude the influence of the haemoconcentration caused by HD. Plasma IR-NPY concentrations before and after HD in 71 patients undergoing maintenance HD were 413 +/- 94 pg/ml and 340 +/- 90 pg/ml (mean +/- SD), respectively. Plasma IR-NPY concentrations before HD in 28 hypertensive patients with HD (398 +/- 91 pg/ml) were not significantly different from those in 40 normotensive (427 +/- 98 pg/ml) and 3 hypotensive (372 +/- 21 pg/ml) patients with HD (P greater than 0.1). Plasma IR-NPY concentrations after HD in 9 patients whose systolic blood pressure fell more than 30 mmHg during HD (409 +/- 52 pg/ml) were significantly higher than those in the other patients (P less than 0.025). These findings suggest that the release of NPY is increased when the blood pressure falls during HD in patients undergoing maintenance HD.