PERINATAL LUNG INJURY EXTENDS IN ADULTS THE SITE OF HYPOXIC PULMONARYVASOCONSTRICTION UPSTREAM

Adult rats born in hypoxia but raised in air are more reactive to acut e hypoxic challenges. The relation between perfusion pressure and perf usion flow (P/Q plot) was analyzed in the preparation of ventilated pe rfused Lungs isolated from 3 groups of adult rats. Control animals of the first group were born and lived in air, the second group was born in hypoxic chamber and then the rats were raised in air. Rats of the t hird group were born in air and exposed to hypoxia in adulthood. The P /Q plot in rats torn in hypoxia had lower slope than that in controls. Acute hypoxia in control group resulted in parallel shift of P/Q line to higher pressures. In rats born in hypoxia, however, both intercept with pressure axis and slope were increased. This may be exlained by the participation of both collapsible and non-collapsible parts of pul monary vascular bed in hypoxic pulmonary vasoconstriction. Analysis of distribution of pulmonary vascular resistances by the double occlusio n technique confirmed :his possibility. In rats born in hypoxia both a rterial and middle vascular segment resistances increased during acute hypoxic challenge. in control rats, however, the increase in resistan ce was restricted to the middle segment only.