Effects of a two-year inhalation exposure of rats to coal dust and/or diesel exhaust on tension responses of isolated airway smooth muscle.
This study was performed to determine whether chronic inhalation exposure of rats to levels of coal dust (CD) and/or diesel exhaust (DE) similar to those experienced by underground miners affects the pharmacologic characteristics of the animal's airway smooth muscle. Animals were exposed for 2 yr to CD alone (2 mg/m3 of respirable particulates), DE alone (2 mg/m3 of respirable particulates), or CD and DE (CD + DE) in combination (1 mg/m3 CD plus 1 mg/m3 DE). Concentration-response relationships for tension changes induced with acetylcholine, 5-hydroxytryptamine, potassium chloride, and isoproterenol were assessed in vitro on isolated preparations of rat airway smooth muscle (trachealis). Compared with control animals, the maximal contractile responses to acetylcholine of tissues from CD-, DE-, and CD + DE-exposed animals were significantly increased; the effects of CD and DE exposure were additive. The CD + DE exposure, but not the individual treatments, resulted in a significant increase in the maximal relaxation response elicited by isoproterenol; this interaction may have resulted from the addition of, or the synergism between, the nonsignificant effects of CD and DE alone. No treatment altered the sensitivity (EC50 values) of the muscles to the agonists used. The results indicate that chronic exposure to CD, DE, and CD + DE produces differential modifications in the behavior of rat airway smooth muscle. These findings may have some bearing on humans exposed to these substances.
D000281:Administration, Intranasal; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D003031:Coal; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005648:Fuel Oils / Q000633:toxicity*; D008906:Mining; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000473:pathology; D010578:Petroleum / Q000633:toxicity*; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors; D014132:Trachea / Q000187:drug effects* / Q000473:pathology
D003031:Coal; D005648:Fuel Oils; D010578:Petroleum