Direct in vitro effects of meconium on airway reactivity in adult rabbits.

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).