Atrial natriuretic peptide--the influence of various physiological and sampling conditions.

A study of various physiological conditions, possibly influencing levels of atrial natriuretic peptide (ANP), is described. Atrial natriuretic peptide was determined by a radioimmunoassay, suitable for routine measurements, using 1 mL of human plasma. Atrial naturetic peptide was adsorbed onto Sep-pak C-18 cartridges, eluted with acidified ethanol and subsequently radioimmunoassayed. The detection limit was slightly less than 2 pg/tube (approximately 5 pg/mL plasma). Intra- and interassay coefficients of variation were 7 and 10%, respectively. Study of various sampling conditions revealed that blood sampling in EDTA-tubes kept on ice, and centrifuged within 1 h, gives the most reliable results. Reference values in 74 individuals ranged between 10 to 69 pg/mL (mean +/- SD = 30 +/- 11 pg/mL). We observed no difference in reference values when the blood sampling procedure was in the sitting (29 +/- 11 pg/mL, n = 43) or supine (31 +/- 12 pg/mL, n = 31) position. Venepuncture stress did not consistently change ANP-levels. No difference was observed in ANP between the follicular and the luteal phase of the menstrual cycle. ANP levels of 7 ambulant female subjects declined significantly during the study period from 7 a.m. to 3 p.m.

The syndrome of hypertension and hyperkalaemia with normal glomerular function (Gordon's syndrome). A pathophysiological study.

A 14-year-old boy with the syndrome of hypertension and hyperkalaemia with normal glomerular filtration rate (Gordon's syndrome) is described. The patient's clinical symptoms consisted of periodic paralysis, slight metabolic acidosis of the proximal type and hypercalciuria. Prostaglandin excretion was normal. Infusion of atrial natriuretic peptide had no effect on electrolyte excretion or glomerular function although a normal increase in cyclic guanosine monophosphate was demonstrated in plasma and urine. This lack of sensitivity to atrial natriuretic peptide offers a new pathophysiological concept in this syndrome. Treatment with hydrochlorothiazide was successful in this case.