Corticosteroid administration modifies ozone-induced increases in sheep airway blood flow

R. A. Gunther, M. A A Yousef, Edward S Schelegle, Carroll E Cross

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Abstract

Recently, we have shown that exposure of intubated conscious sheep to 3 to 4 ppm ozone (O3) for 3 h increases bronchial blood flow (Q̇br). The purpose of the present study was to assess the potential role of corticosteroids in modulating this increase. Six nasally intubated sheep were exposed to filtered room air, 3.5 ppm O3 on two separate occasions, and 3.5 ppm O3 plus methylprednisone, for 3 h. Q̇br was measured using a chronically implanted 20 MHz pulsed Doppler flow probe. Q̇br, mean aortic pressure, cardiac output, pulmonary artery pressure, arterial blood gases, and core temperature were monitored. After 3 h of 3.5 ppm O3, Q̇br increased from 3.2 ± 0.5 (mean ± SEM) to 8.5 ± 1.6 KHz, whereas bronchial vascular resistance (BVR) decreased from the baseline value of 43.6 ± 8.0 to 15.0 ± 3 mm Hg/KHz. With corticosteroids, baseline Q̇br was 3.2 ± 0.6 and BVR was 44.2 ± 9.7; after 3 h of 3.5 ppm O3, Q̇br was 3.3 ± 0.5 KHz and BVR was 39.0 ± 8.0 mm Hg/KHz. The two 3.5-ppm O3 exposures without corticosteroids were impressively reproducible. Except for Q̇br and BVR, no other measured cardiovascular parameters were affected by O3. The results indicate that corticosteroids are capable of interfering with mediator, neurohumoral, or inflammatory cell mechanisms responsible for vasodilation of the airway microcirculation after O3 exposure, but do not specifically address the specific processes whereby this attenuation occurs.

Original languageEnglish (US)
Pages (from-to)660-664
Number of pages5
JournalAmerican Review of Respiratory Disease
Volume146
Issue number3
StatePublished - 1992

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ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

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