CIRCULATING ANGIOTENSIN-CONVERTING ENZYME, VON-WILLEBRAND-FACTOR ANTIGEN AND THROMBOMODULIN IN EXERTIONAL HEAT-STROKE

1. Military recruits frequently succumb to exertional heat stroke duri ng intensive training. Since widespread endothelial injury is often as sociated with exertional heat stroke, the relationship between changes in three circulating endothelial cell markers (angiotensin-converting enzyme, von Willebrand factor antigen and thrombomodulin) and exertio nal heat stroke was studied. 2. Twelve recruits who had succumbed to e xertional heat stroke during basic physical training (5000 m running) were included in the study. Another 10 age-matched healthy subjects wh o had gone through the same physical training regimen were selected as controls. 3. Blood was withdrawn on admission and on discharge for an alyses of angiotensin-converting enzyme, von Willebrand factor antigen and thrombomodulin. Other physiological parameters and biochemical an alyses reflecting renal and liver functions were also recorded. 4. Our results indicated that these subjects with exertional heat stroke exh ibited impaired liver function as revealed by the significant elevatio n of both serum glutamic oxaloacetic transaminase (P<0.05) and serum g lutamic pyruvic transaminase (P<0.05) as compared with normal healthy control subjects. Unfortunately, these values remained mostly somewhat elevated on discharge, although serum glutamic oxaloacetic transamina se was reduced dramatically. Indices of kidney functions, including cr eatinine clearance and uric acid and phosphorus secretion, were not si gnificantly different from those observed in healthy controls. 5. Circ ulating angiotensin-converting enzyme activities in exertional heat st roke patients on admission were significantly lower than in normal sub jects (10.68 +/- 2.15 versus 21.21 +/- 3.18 nmol hippuric acid min(-1) ml(-1), P<0.05). In contrast, von Willebrand factor antigen, thrombomo dulin and plasma renin activity were significantly elevated compared w ith corresponding values in healthy subjects (P<0.001, 0.05 and 0.01 r espectively). The values of these endothelial markers returned to norm al on discharge. 6. These data suggest that the decrease in angiotensi n-converting enzyme and increase in von Willebrand factor antigen and thrombomodulin associated with exertional heat stroke may reflect endo thelial injuries. Since endothelial injuries may trigger haemostatic f ailure and/or disseminated intravascular coagulation, the monitoring o f these values might be useful for the evaluation of endothelial statu s in patients suffering from exertional heat stroke.