EFFECT OF ACUTE ADMINISTRATION OF BLEOMYCIN ON LUNG FLUID BALANCE IN SHEEP

This study examined the effects of acute administration of bleomycin ( BLM) on lung liquid and protein exchange in anesthetized sheep prepare d with caudal mediastinal lung lymph fistulas. Six sheep received BLM (15 U IV) after a baseline period, while seven others were given BLM a fter a steady state was obtained following elevation of left atrial pr essure (P-LA) a procedure intended to minimize changes in pulmonary mi crovascular surface area and produce high lung lymph flow (Q(L)). Plas ma and lung lymph angiotensin converting enzyme (ACE) activities were measured in order to independently assess the effects of BLM on pulmon ary endothelial integrity. Q(L) rose significantly in all animals foll owing BLM. The ratio of lymph to plasma protein concentration (C-L/C-P ) did not change in the group given BLM alone, and fell continuously d uring the period of P-LA elevation after BLM in that group. Plasma and lung lymph ACE activities were unchanged following BLM administration in either group. The ultrastructure of the gas-exchanging region of l ungs from animals in each group was examined by transmission electron microscopy. The data suggest that acute administration of a low dose o f BLM does not increase pulmonary microvascular permeability, but may induce an increase in perfused pulmonary microvascular surface area re sponsible for increased Q(L).