Mechanical control of initial lymphatic contractile behavior in bat's wing.

The initial lymphatics of the bat's wing demonstrate spontaneous rhythmical contractions that contribute to the active formation of lymph. In the present study, modulation of lymphatic activity by mechanical factors was examined. Oil was injected to block the outflow tract of individual initial lymphatic bulbs to create a state of near isovolumetric contraction. Pulse pressure, base-line pressure, and contractile frequency were measured with the servo-null technique, while base-line pressure within the bulb was controlled by the infusion or withdrawal of fluid. Increasing the base-line luminal pressure from its resting level (near atmospheric pressure) produced an increase in pulse pressure up to an optimal level and then a subsequent decline in pulsatile strength. The magnitude of the pulsations changed by three to four times over the range of distending pressures. Contractile frequency increased 14% over the same range.