[Contractions of the lymphangion under low filling conditions and the absence of stretching stimuli. The possibility of the sucking effect].

Regulation of the function of the lymphatic pump is tightly connected to the degree of filling of the lymphangion. This mechanism is one of the principle ways that the lymphatics self-regulate lymph transport. But interpretation of the causes and consequences of this regulation is still far from perfect. The issue of whether automatism of electrical activity of the lymphatic smooth muscle cells or the distension of the cell membranes first causes depolarization, is a principal question which needs answering in order to understand the control of lymph transport. In our experiments with perfused isolated bovine mesenteric lymphangions, different values of lymph pressure were simulated. For this purpose, lowfrequency sinusoidal fluctuations of the input pressure were applied to lymphangions under conditions of regulated filling. A poor correlation was seen between lymph pressure fluctuations and lymphangion contractions, as well as between the rate of lymphangion filling and contractions. We observed stable spontaneous contractions of both bovine and rat mesenteric lymphangions at 0 cm of water intralymphatic pressure, and in the absence of distension stimuli (both radial and axial stretch). Under conditions of low filling, contractions of bovine lymphangions produced negative intralymphatic pressure and a suction effect. The automatism is an inherent feature of the lymphatic smooth muscle cells. Distension of the lymphangion modulates the electrical characteristics of the membranes and thus the contractile mechanisms in lymphangions.