Document peLROg4gmXYBkQb75B18Bo0oj

EXPERIMENTAL ABBESTOS1B--GROSS A BE TREV1LLE 647 The reaction of the hamster lung to chrys the considerably larger amount of acid-insol olite dust is the antithesis of that observed uble mineral ash demonstrable in the ham in rats. The lesion extends from the proxi ster lung sections than in those of rata Fur mal portion of the recemus to the peripheral ther evidence is seen in the diffuseness of the alveoli, thereby producing extensive consoli dust distribution in the hamster (Fig 9) in dations in the hamster lungs. The consolida contrast to its restriction to the proximal tions are composed of obliterated air spaces, portion of the raoemus as in the rat (Fig 5). the lumens of which are filled with masses of The reactivity of hamster tissue to chryso- alveolar cells, mostly desquamated (Fig*6). tile fibers is significantly different from that Although the inflammation involves the en of rat tissue, the former being much more tire raoemus in this animal, the proximal florid. This is seen not only in the plentiful portion shows more severe involvement production of asbestos bodies in hamster than the peripheral portion. It is this ex lungs but also in the failure of argyrophilic tensiveness of asbestotic involvement with precollagenous fibers to mature into colla consequent pulmonary inadequacy that ac gen as well as in the undiminishing oellulari- counts for the high mortality of the ham ty of the inflammatory tissue even after a sters. lapse of nearly two years. This difference in With the previously given definition of the reactivity of lung tissue in the rats on the progression in mind, it is seen that the one hand and in hamsters on the other is not diffuse involvement of the raoemus in the unique to chryBotile dust inasmuch aa simi hamster would fit the first requirement for lar and quite comparable differences in progressiveness of the disease, if it can be these two species have been noted in their shown that the inflammation originally was reactivity to quartz dust.10 confined to the proximal portion of the ra- It is highly probable that interspecies cemus and then extended into the peripheral differences in the efficiency of the pulmo air spaces. This information, unfortunately, nary clearance mechanism play an impor is not available from the present investiga tant role in the susceptibility of the different tion. However, the finding of a more severe species to certain pulmonary diseases. It is involvement of the proximal portion of the recognized, for example, that horses and raoemus favors the probability that such an mules working during their lifetime in mines extension took place. The second require exposed to quartz dust will have accumulat ment of progression, ie, that the inflamma ed a negligible amount of silica in the lungs tion remain active and nonhealing, is a con and will demonstrate no silicosis;1' whereas spicuous feature of the asbestotic hamster miners in the same workings will have vary lungs. The failure of the argyrophilic fibers ing degrees of silicosis as well as a sig to lose their arborescenoe and to oollagenize nificantly elevated pulmonary silica content. and the persistence of the extreme cellulari- We have recently exposed rats and mioe si ty of the involved tissues nearly two years multaneously to quartz dust in the same in after the intrapulmonary dust deposition is halation chamber for the same length of incontrovertible evidence of nonhealing. time. All animals were killed immediately Two possible explanations come to mind after the end of the dust exposure. Wellfor the difference in the disease produced in defined silicotic nodules were present in the the rat and the hamster by the same chryso rat lungs; whereas, the mouse lungs were ab lite dust. One explanation is that the reactiv solutely normal, and no add-insoluble dust ity of hamster tissue to the dust is greater could be demonstrated in the mouse-lung than that of rat tissue. The other is that the sections after miooindneration (unpub hamster's alveolar clearance mechanism is lished data). not as capable as that of rats in transporting The above observations are relevant to the dust from the peripheral air spaces prox- the present investigation insofar as such in- imally. As will be seen below, both explana torspedes differences tend to make extrapo tions apply. lation from animal data to human disease There is some evidence that the hamster's unreliable. The questions to be resolved are pulmonary clearance mechanism is not as whether the efficiency of the clearance effective as that of the rat. This is seen in mechanism of man approximates that of the Arch Environ Health--Vol IS. Nov 1967 t I 8005 1467 PRODUCED BY FORD