The release of a bradykinin‐like pulmonary vasodilator substance in foetal and new‐born lambs

Abstract

SUMMARY1. Exposure to glass of whole blood from anaesthetized foetal lambs (at 0-6-0-95 of term) causes the rapid development of a potent pulmonary vasodilator agent.2. The formation of the vasodilator agent on exposure to glass, its disappearance with time, and the inhibition of its production by soya bean trypsin inhibitor, suggest that it is bradykinin.3. Small doses of bradykinin (, 1 ng/kg) cause pulmonary vasodilatation on close arterial injection. Neither this, nor the vasodilatation caused by glass-exposed whole blood, are affected by agents which block the vasodilator actions of acetylcholine, isoprenaline or histamine.4. Exposure of foetal plasma and/or red cells to glass rarely caused the development of a pulmonary vasodilator agent. Maternal plasma was always active. Injection of the buffy coat from foetal blood caused pulmonary vasodilatation.5. The capacity of plasma from sheep at different ages to produce kinin(s) was examined by assay on the isolated rat's uterus. In the foetus activity was very low; it increased with age.6. In adolescent lambs 5-14 weeks after birth injection of 10 ng/kg bradykinin into the pulmonary artery caused only a trifling vasodilata-* Present address:

The release and fate of vaso‐active hormones in the circulation

“…The release and fate of vaso-active hormones in the circulation sensitive to bradykinin (Campbell, Dawes, Fisherman, Heyman & Perks, 1968). These authors also conclude that some vasodilator effects obtained in perfusion experiments using glass connections are due to glass-activated formation of a plasma kinin.…”

Physiologic characterization of endothelin A and B receptor activity in the ovine fetal pulmonary circulation.

“…Although mechanisms maintaining high pulmonary vascular resistance in the fetus are uncertain, possible explanation for this high resistance include lack of an air liquid interface or ventilation, low oxygen tension (2-7), decreased vasodilators, such as prostacyclin, bradykinin or endothelium-derived nitric oxide or increased vasoconstrictors such as platelet activating factor or leukotrienes (28)(29)(30)(31)(32)(33)(34)(35)(36)(37). Endothelin has potent vasoconstrictor properties (9), but its role in the fetal lung is poorly understood.…”

Accelerating and Retarding Effects of Dexamethasone on the Development of the Avian Lung

“…As suggested by Campbell et al [1968] and Melmon et al [1978], induction of pul monary circulation is mediated through bradykinin (ornithokinin) by reducing the pul monary vascular resistence, so that blood flows preferentially to the lungs. As demon strated in table II the increase of ornithokallikrein activity proceeded in parallel with the enhancement of the pulmonary hemoglobin content.…”