Endocrine status and LBNP-induced hormone changes during a 438-day spaceflight: a case study

We investigated basal levels and lower body negative pressure (LBNP)-induced changes of volume regulating (PRA, aldosterone, AVP, ANP99-126) and other stress-sensitive hormones (catecholamines, cortisol, ACTH) in venous plasma from one cosmonaut before (-45 d), during (3, 170, 287, 430 d) and after (+4, +90 d) a record-breaking long-term (438 d) spaceflight. Blood was taken at the beginning and immediately after ending LBNP (-15/-30/-35 mm Hg for 15/15/10 min, respectively) preflight supine, inflight, and postflight supine. PRA, aldosterone, and vasopressin levels stayed within normal boundaries during the entire flight and after landing. Catecholamines exceeded reference limits (epinephrine > 140 pg x ml(-1), norepinephrine >1000 pg x ml(-1) 5 and 9 mo inflight, and 4 d postflight. ANP and cGMP were lower inflight (p<0.04) than pre- or postflight. Cortisol and ACTH were not consistently altered. LBNP-induced hormonal changes were not different (p>0.05) in microgravity and 1-G. Based on data from one cosmonaut, we conclude that long-term spaceflight up to 430 d duration appeared to lower plasma ANP and cGMP during flight and occasionally elevate catecholamine levels, without significantly altering LBNP-induced relative hormone changes as compared with those observed on the ground.