Effects of Prostaglandins on the Pulmonary Vascular Bed of Newborn Rats with Chronic Hypoxia

Abstract

We investigated the effects of prostaglandins (PG) E₁, I₂ and D₂ on the pulmonary vascular bed of newborn rats subjected to chronic hypoxia. Forty seven newborn rats were exposed to chronic hypoxia (10% oxygen) for 23 days and divided into five groups which received PGE₁ (N=10), PGI₂ (N=9), PGD₂ (N = 11), placebo (N=9) or served as controls (N=8). The PG's were administered by implanting slow release subcutaneous pellets delivering an average daily dose of 1 μg. Thirteen newborn rats in room air received either placebo or served as controls. All rats were killed after 23 days and heart-lung preparations were perfusion fixed with glutaraldehyde. Appropriate blocks were processed for quantitative morphometry of the pulmonary parenchyma, arteries and arterioles. For analysis the pulmonary vessels were grouped by external diameter, i.e. 30-50μ and 50-100μ. External diameter/lumen diameter, an index of medial smooth muscle mass, was 1.39 ± 0.02 in room air controls, this index of medial muscle mass was significantly increased (p < 0.01) to 1.53 ± 0.03 in hypoxic controls and the PGD₂ and PGI₂ groups. However, the PGE₁ group did not have medial hypertrophy evidenced by a medial muscle mass index of 1.34 ± 0.04, similar to room air controls. These findings suggest that PGE₁ may prevent the development of medial hypertrophy that occurs in chronic hypoxia.