Alterations in the volume stimulus-renal response relationship during exposure to simulated microgravity.
J Gravit Physiol
; 6(2): 1-9, 1999 Oct.
Article
en En
| MEDLINE
| ID: mdl-11543080
We measured central venous pressure (CVP), plasma volume (PV), urine volume rate (UVR), and circulating hormones (renin activity (PRA), vasopressin (AVP), atrial natriuretic peptide (ANP), and cortisol) before and after acute volume infusion (Dextran-40) to test the hypotheses that head-down tilt bedrest (HDT) caused (1) a resetting of the CVP operating point and (2) attenuated urine excretion. Six rhesus monkeys underwent two experimental conditions (HDT and control, each of 48 hour duration) with each condition separated by nine days of ambulatory activities to produce a cross-over counterbalance design. One test condition was continuous exposure to 10 degrees HDT and the second test condition was a control, defined as approximately 12-14 hours per day of 80 degrees head-up tilt and 10-12 hours prone. Following 48 hours of exposure to either test condition, 20-minute continuous infusion of Dextran-40 was administered. CVP in HDT was lower than the control condition. Similar elevations in CVP occurred 30 min post-infusion in both test conditions, and returned to pre-infusion baseline levels between 22 and 46 h post-infusion in both treatments. The UVR response during infusion was attenuated by HDT despite similar elevation in CVP. Elevation in ANP and reduction in PRA at the end of infusion were greater in Control compared to HDT. No differences between control and HDT were detected for AVP and cortisol responses to infusion. Since CVP returned to its pre-infusion levels following volume loading in HDT and control conditions, it appeared that the lower CVP may reflect a new operating point about which vascular volume is regulated. Further, attenuated ANP and PRA responses during vascular volume loading may contribute to depressed UVR in low gravity exposure.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Volumen Plasmático
/
Presión Venosa Central
/
Dextranos
/
Sustitutos del Plasma
/
Simulación de Ingravidez
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
J Gravit Physiol
Asunto de la revista:
FISIOLOGIA
Año:
1999
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos