APStracts 2:0122A, 1995.

Effect of microgravity on forearm subcutaneous vascular resistance in humans. Gabrielsen, Anders, Peter Norsk, Regitze Videbaek, and Ole Henriksen. Danish Aerospace Medical Centre of Research and Clinic of Aviation Medicine, Rigshospitalet 7522, DK-2200 Copenhagen; and Dept. of Magnetic Resonance., Hvidovre Hospital, DK-2650 Hvidovre, Denmark.

APStracts 2:0122A, 1995.

To test the hypothesis that the subcutaneous vascular constrictor response to an orthostatic stress in humans is augmented after exposure to microgravity, the following experiment was performed. Four male astronauts underwent a standardized, stepwise lower body negative pressure (LBNP) profile 5 months before and between 24 and 40 hrs after completion of the 10-day Spacelab D2-mission (STS-55). Forearm subcutaneous blood flow (FSBF) was continuously measured during LBNP by the 133Xenon washout technique and forearm subcutaneous vascular resistance (FSVR) was estimated by dividing mean arterial pressure by FSBF. Relative to the pre-LBNP level, FSVR increased to 169+/-42% (p<0.05), 176+/-12% (p<0.05), and 158+/ -27% during postflight LBNP of 11 (20 min), 23 (5 min) and 30 (7.5 min) mmHg, respectively. During the same LBNP-levels of same durations preflight, FSVR increased to 121+/-11% (NS), 139+/-12% (p<0.05), and 135+/-13% (p<0.05). Thus, FSVR increased more promptly and in 3 of the 4 subjects more pronounced during postflight than during preflight LBNP. In conclusion, the FSVR-response was more prompt and tended to be accentuated after 1-2 days following exposure to 10 days of microgravity and could act as a defense mechanism to alleviate decreased orthostatic tolerance.

Received 12 August 1994; accepted in final form 16 March 1995.
APS Manuscript Number A847-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 March 1995.