Pulmonary capillary endothelial metabolic function in chronic thromboembolic pulmonary hypertension.
BACKGROUND
Chronic thromboembolic pulmonary hypertension (CTEPH) causes physical plugging of large pulmonary arteries as well as a distal micro-vasculopathy. Pulmonary endothelium is an active metabolic tissue in normal humans. The effects of CTEPH on pulmonary endothelial metabolism are unknown.


OBJECTIVE
We studied pulmonary capillary endothelium-bound angiotensin converting enzyme (ACE) activity as an index of endothelial metabolism in patients with CTEPH.


METHODS
We measured single-pass transpulmonary per cent metabolism (%M) and hydrolysis of an ACE synthetic substrate and calculated functional capillary surface area (FCSA), normalized to body surface area (BSA), in 13 patients with CTEPH and 23 controls.


RESULTS
Mean %M for CTEPH (71.6 +/- 4.0% SE) was similar to controls (74.7 +/- 2.7%). Substrate hydrolysis (v) was similar for CTEPH (1.47 +/- 0.22) and controls (1.51 +/- 0.11). However, FCSA/BSA was reduced (P < 0.01) for CTEPH (1530 +/- 218 mL min(-1)*m(-2)) as compared with controls (2948 +/- 245).


CONCLUSIONS
The metabolically functional pulmonary capillary bed is reduced in CTEPH. However, because %M and hydrolysis are preserved, this points to a reduction in functional capillary surface area rather than reduced ACE activity on the pulmonary capillary endothelial cell. The reduction in functional capillary surface area may just be a result of decreased capillary recruitment because of upstream vascular plugging by chronic organized thrombus.
Second Department of Critical Care, University of Athens Medical School and Pulmonary Hypertension Clinic, Attikon Hospital, Athens-Haidari, Greece.
S E
SE
Orfanos
A M
AM
Hirsch
M
M
Giovinazzo
A
A
Armaganidis
J D
JD
Catravas
D
D
Langleben
D002196:Capillaries / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D002908:Chronic Disease; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D007700:Kinetics; D008168:Lung / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D013923:Thromboembolism / Q000150:complications / Q000378:metabolism* / Q000473:pathology
D007703:Peptidyl-Dipeptidase A