Introduction: Meconium aspiration syndrome (MAS) is a serious neonatal disease with multifactor pathogenesis and long-term sequelae on the developing respiratory system. Since the altered airway reactivity may play a role in MAS, this study investigated whether 1 hour-lasting in vitro incubation of rabbit tracheal and lung tissue strips with meconium would also increase the airway reactivity.
Methods: Trachea and lungs of adult healthy rabbits were excised. Smooth muscle reactivity was estimated by an in vitro method using organ chambers. After the adaptation of tissue strips, 1 ml of suspended meconium (Meconium) was added into two chambers with one tracheal and one lung strip for another 1 hour. The two other chambers were incubated only with Krebs-Henseleit's buffer (Control). Cumulative doses of histamine (10(-8)-10(-3) mol/l) were added after finishing the incubation period and a continuous recording of contractions was made.
Results: The contractile response of the lung tissue smooth muscle to histamine was recorded to decrease non-significantly in Meconium group when compared to Control group. The tracheal tissue reactivity to histamine at concentrations of 10(-8)- 10(-4) mol/l was lower in Meconium group than in Control group. Significant differences appeared only at concentrations of 10(-8), 10(-7), and 10(-6) mol/l (p=0.041, p=0.033, and p=0.019, respectively).
Conclusions: One-hour-lasting in vitro incubation of tracheal and lung tissue strips with meconium significantly decreased the tracheal reactivity to histamine and slightly, but non-significantly decreased the lung tissue reactivity to histamine (Fig. 1, Ref. 6).