The influence of volume depletion and central hypovolemia on the plasma concentration of parathyroid hormone in dialysis patients.
Because changes in extracellular volume during dialysis cause reflex neurohonnonal changes that may influence parathyroid hormone (PTH) release independently of calcium, the influence of isotonic volume depletion (by isolated ultrafiltration) and central hypovolemia (70 degrees tilt) on serum PTH1-84 was studied in 16 hemodialysis patients. Tilting was performed in volume depleted state, i.e., immediately after hemodialysis. In the control study, patients underwent sham ultrafiltration (UF = 0) and after dialysis maintained the supine position for the same length of time they remained in the tilt position in the active experiment. Isolated ultrafiltration (-2.3 +/- SEM 0.3 L) caused a 21% fall in mean arterial pressure (from 101 +/- 6 to 80 +/- 6 mmHg, P < 0.01), a fall that was accompanied by a marked increase in plasma catecholamine levels (norepinephrine P < 0.001, epinephrine P < 0.025), in plasma renin activity (P < 0.001) and in plasma arginine vasopressin (P < O.001). Atrial natriuretic factor showed a slight reduction, whereas the plasma endothelin-1 level did not change. Serum Ca showed the expected, hemoconcentration-dependent rise (from 4.1 +/- 0.1 to 4.4 +/- 0.1 meq/L, P < 0.01). Interestingly, UF caused a marked rise in plasma PTH1-84 concentration (from 252 +/- 62 to 335 +/- 72 pg/ml, P < 0.01). UF-induced changes in serum PTH1-84 were related to norepinephrine changes (r = 0.57) as well as to plasma renin activity (r = 0.50). After hemodialysis, tilting induced a pronounced rise in serum PTH1-84 (from 102 +/- 29 to 200 +/- 55 pg/ml), and these changes were slightly related to plasma epinephrine (r = 0.49) but independent of other parameters. In the control experiment, neither sham UF nor recumbency modified serum PTH. In hemodialysis patients, serum PTH is sensitive to changes in extracellular and central blood volume of magnitude sufficient to decrease arterial pressure. Avoiding marked volume stimuli might help to refine the interpretation of the Ca/PTH curves during hemodialysis in these patients.
Mallamaci
F
F
Centro Fisiologia Clinica CNR and Divisione di Nefrologia, Ospedali Riuniti, Reggio Cal, Italy.
Zoccali
C
C
Messineo
L
L
Parlongo
S
S
Postorino
M
M
D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood; D002118:Calcium / Q000097:blood; D004837:Epinephrine / Q000097:blood; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018377:Neurotransmitter Agents / Q000502:physiology; D009638:Norepinephrine / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood*; D011187:Posture / Q000502:physiology; D012018:Reflex / Q000502:physiology; D006435:Renal Dialysis / Q000009:adverse effects; D012083:Renin / Q000097:blood; D014462:Ultrafiltration
D018377:Neurotransmitter Agents; D010281:Parathyroid Hormone; D001127:Arginine Vasopressin; D012083:Renin; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine