Local Chemical and Nervous Control of Consecutive Vascular Sections in the Mesenteric Lymph Nodes of the Cat

Abstract

A method which made it possible to follow continuously and simultaneously the reactions within the consecutive vascular sections has been used to study blood flow through the lymph nodes around the mesenteric root of the cat. The acutely sympathectomized resistance vessels showed a considerable basal tone at "rest" as judged by the fact that blood flow could be increased from a "resting" value of 20-60 up to 180 ml/(min X 100 g). When the blood flow increased, capillary filtration coefficient (CFC) also increased from a "resting" value of 0.01-0.05 up to 0.12 ml/(min X mm Hg X 100 g). Regional blood volume of the mesenteric lymph nodes was estimeated as 7-10 ml/100 g tissue at "rest" and could be increased some 20% at most by dilating agents. Graded stimulation of the regional sympathetic fibres caused a constriction of both the resistance and the capacitance vessels. The constrictor response of the resistance section consisted characteristically of 2 phases. First, there was a peak response maintained for about 1 min. After this, the constrictor response declined in spite of maintained nerve stimulation and with 2-3 min reached a steady state level during which blood flow resistance was increased at most 50-100% above control level. In spite of increasing blood flow, CFC stayed low during prolonged stimulation periods. Maximal constriction of the capacitance section could expel about 40% of the regional blood content.