J.Jpn. Surg. Soc.. 86(5): 527-533, 1985

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Original article

CIRCULATING NEGATIVE INOTROPIC SUBSTANCE PRODUCED FROM THE LUNG, AFFECTED WITH PROSTAGLANDIN AND THROMBOXANE

The Lung is capable of the synthesis and the release of prostaglandins responded to a number of pathophysiological stimuli, which may impair myocardial performance. Present study was undertaken to determine the release of circulating negative inotropic substance(s) from the lung and whether or not blockage of prostanoid synthesis, or infusion of prostaglandin are related to the production of this substance(s).
Sixteen isolated left lower lobes were divided into 3 groups : (1) untreated, isolated blood-perfused lungs (n=5), (2) prostaglandin I₂, 1μg/min, continuously added to the perfusate (n=6), and (3) five lobes preteated with ibuprofen (12.5mg/kg) in addition to 1μg/min prostaglandin I₂. Perfusion of an isolated lobe with heparinized whole blood caused thrombocytopenia. The plasma 4 hours after perfusion led to the generation of a humoral agent(s) that reduced developed tendion (Tpd) of a papillary muscle (p＜0.05), and Ca⁺⁺-and Mg⁺⁺-ATPase of sarcoplasmic reticulum (SR) (p＜0.01).
With prostaglandin I₂, thromboxane B₂ rose from 0.076 to 0.362ng/ml at a Ievel higher than control (p＜0.05). The plasma significantly lowered SR-ATPase and myofibril-Mg⁺⁺-ATPase activities and further reduced papillary muscle Tpd. By pretreatment with ibuprofen, adverse prostaglandin II₂ effects were eliminated.
The observation suggests that the lung produces prostaglandin related negative inotropic substance(s) that may reduced contractility, affected by energy availability.

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