Mast Cells and Antigen Response of Airway Smooth Muscle

We have recently observed that resensitization of sensitized guinea pigs caused a significant increase in the resting membrane potential of airway smooth muscle cells (ASM). To establish whether mast cells were involved in these changes, we investigated the effect of disodium cromoglycate (DSCG) and substance 48/80 on isolated airway smooth muscle preparations. We determined the contractile response of ASM, and resting membrane potential both before and after the administration of DSCG, substance 48/80 and a specific antigen (1% ovalbumin). We measured resting membrane potential with 3 M KC1-filled glass micro-electrodes with an impedance between 80-90 M omega. It was found that: (1) DSCG did not have any measurable effect on ASM of control animals. Before the administration of DSCG the membrane potential of the control ASM was -61.8 +/- 0.6 mV. After DSCG the membrane potential was -61.5 +/- 0.5 V. (2) DSCG caused a slight relaxation (p less than 0.05) of ASM from resensitized animals with no detectable change in membrane potential. ASM cells of resensitized animals remained hyperpolarized (i.e., resting membrane potential = -78.2 +/- 0.1 mV). (3) In the presence of DSCG contractile and electrical responses after the administration of 1% ovalbumin were biphasic (4) Substance 48/80 caused a small contractile response in ASM from controls, and a significant contractile response (p less than 0.001) with a corresponding change (p less than 0.001) in the membrane potential in ASM of the resensitized animals. (5) After the administration of 1% ovalbumin, the response of preparations pretreated with substance 48/80 was decreased by 24% (p less than 0.001) as measured by isometric force and 13% (p less than 0.001) as measured by membrane potential. It is concluded that pharmacological manipulation of mast cells in sensitized airway smooth muscles failed to influence the membrane potential of these cells and only partially influenced the physiological response of the tissue to a specific antigen.