To localize the stores of catecholamines present, normal rat lungs were examined with a histochemical fluorescence technique. Comparison was made with sections from animals infused with methylene blue to demonstrate the autonomic innervation usually observed. A n extensive network of fine fluorescent fibers was seen in the mucosa of the entire bronchial tree. Coarse interstitial fibers adjacent to bronchi represented the largest monoamine stores observed, and communicated by delicate fibers with both the musculature and mucosa. Arterial fluorescence was less prominent, and a continuous subendothelial layer of coarse fluorescent material communicated with finer fibers in the muscular walls. The extensive fluorescent fibrous network visualized with the present method, demonstrating fine details of innervation, suggested a n intimate relation between the bronchi and pulmonary arteries.Catecholamines in a dry protein layer exposed to formaldehyde gas are transformed into products with an intense green to yellow-green fluorescence (Falck et al., '62). This reaction has been studied with the use of model systems, and its chemical specificity reported (Corrodi and Hillarp, '63, '64). This method has been utilized for the cellular localization of monoamines in the adrenal medulla (Falck and Torp, '61), brain (Dahlstrom and Fuxe, '64) and adrenergic fibers in various organs and tissues (Angelakos et al., '63). Because of the relatively high concentration of norepinephrine in sympathetic nerve terminals the adrenergic innervation can be readily visualized. In kidney the specific fluorescence is seen only in relation to blood vessels (Nilsson, '65) similar to the vasomotor nerve localization observed in other tissues.Knowledge of the catecholamines stored in the lung may help explain alterations involving the blood vessels and bronchi that often are interpreted as disturbances of the autonomic nervous system. The pulmonary vascular alterations associated with cardiovascular disease are well known morphologically (Hinke, '65) although the arteries of the lung are thought to play a passive role in their development. Increased catecholamine metabolism in congestive heart failure associated with valvular heart lesions where pulmonary ANAT. REC., 156: 19-30.arteriosclerosis is a prominent feature is felt to demonstrate augmented activity of the sympathetic nervous system (Chidsey et al., '65).Experiments with isolated perfused lungs and isolated pulmonary vessels have played a large part in the examination of these reactions (Daly, '61 ). The perfusion technique, of necessity, is abnormal and the lung vessels are consequently less reactive than they are in the intact animal. The present report describes histochemical findings in rapidly processed normal rat lungs. Basic pulmonary pathologic alterations may be interpreted differently with understanding of the finer details of pulmonary innervation and appreciation of monoamine metabolites present.
MATERIALS AND METHODSFemale albino rats weighing 100-150 gm were kept...