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.
Orfanos
S E
SE
Second Department of Critical Care, University of Athens Medical School and Pulmonary Hypertension Clinic, Attikon Hospital, Athens-Haidari, Greece.
Hirsch
A M
AM
Giovinazzo
M
M
Armaganidis
A
A
Catravas
J D
JD
Langleben
D
D
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