Response of the Regional Lymphatic System of the Sheep to Acute Stress and Adrenaline

Abstract

An acute pain stimulus resulted in elevated lymph flow and output of cells from the popliteal lymph node of the sheep in the first 15 min after the stress. Efferent lymph flow increased by an average of 93 % above the mean resting flow and cell output rose by an average of 170% during this period, but by 30 min after the stress, values for both lymph flow and cell output had returned to normal. The cell content of the efferent lymph was significantly higher in the first 15 min after the acute stress and it is suggested that there is a sizeable pool of lymphocytes within the resting popliteal node which can be mobilized into the lymph by an acute stress. A single intravenous injection of 1 mg adrenaline increased the efferent lymph flow in all the sheep examined but gave rise to an increased cell output in only 50 % of the sheep. This indicated that there may be other factors, possibly hormonal, involved in the movement of the pool oflymphocytes out of the regional lymph node following acute stress.Both acute pain stress and adrenaline resulted in an increased afferent popliteal lymph flow and output of cells from the regional tissues in the first 15 min after administration. The results are suggestive of a small pool of lymphocytes in the regional tissues which may be readily mobilized by either acute stress or adrenaline.Part of the increases in efferent and afferent lymph flow observed following acute stress and adrenaline appeared to be due to an increased lymph formation, presumably as a result of an increased capillary pressure. Nevertheless, it is considered that the greater part of the increased flow of lymph from both regions resulted from an accelerated movement of performed lymph.The lymphatic system acts as an important transport system in man and animals, for fluid and protein and also for recirculating lymphocytes. Physiological factors affecting the lymphatic system are thus likely to alter the recirculation of lymphocytes and this in turn could influence processes involved in the immune response. While the process of lymphocyte recirculation [cf.. Gowans, 1966] and its presumed importance in initiating responses to antigen [Gowans, McGregor, Cowan and Ford, 1962; Hall and Morris, 1963;Gowans. and McGregor, 1965;Sprent, Miller and Mitchell, 1971] have been known for some time, little attention has focussed on physiological factors that might alter the cellular traffic in lymph. Previous work in this area has shown the effect of corticotrophic and corticosteroid hormones on the recirculation of lymphocytes [Spry, 1972;Shannon and Jones, 1974] and indicates the need for further work on physiological interactions in the lymphatic system. Moreover, the importance of factors influencing the recirculation of lymphocytes can be inferred from recent work by Zatz and Gershon [1975] which suggests that the regulation of lymphocyte traffic may provide a mechanism for the control of immune responses in vivo.

Lymphatic Innervation

“…This response was undoubtedly a complex one involving many factors other than reflex sympathetic activation since attempts to mimic it by inducing cerebral ischaemia re sulted in a much smaller increase in pump ing activity [29], Emotional Stress. Shannon et al [30] and McHale and Roddie [31] observed that sheep hind limb lymph flow increased when the animals were startled. They suggested that this might be due to a nervous reflex but the results were difficult to interpret since the animal sometimes moved when it was frightened and this in itself is known to increase hind limb lymph flow.…”

Epinephrine causes a reduction in lymph node cell output in sheep

“…Depending on the catecholamine infused, subject, and dosage, biphasic leukocytosis is observed that is comprised of a marked neutrophilia and lymphocytosis, and is followed by a delayed lymphopenia (Burns et al 1997). However, the results examining the effects of Epi on the lymphatic system have been contradictory (Iveson et al 1994;Shannon et al 1976;Steel et al 1971). Therefore, we designed experiments to examine the effects of Epi on lymph volume, cell output, and lymphocyte subsets.…”

Sympathetic stimulation causes increased output of lymphocytes from the popliteal node in anaesthetized sheep

“…McHale & Thornbury (1986) demonstrated a threefold increase in volume of fluid pumped when the sheep's head was held for a period of 1 min. Similarly Shannon, Quin & Jones (1976) showed that lymphocyte output in efferent lymph, as well as lymph flow, was increased in response to painful stimuli. Thus it may be that the role of lymphatic innervation is concemed more with the immunological functions of the lymphatic system than with fluid homeostasis.…”

“…Thus it may be that the role of lymphatic innervation is concemed more with the immunological functions of the lymphatic system than with fluid homeostasis. The present study seeks to establish whether the sympathetic nervous system can mimic the lymphocytosis in response to an acute pain stimulus reported by Shannon et al (1976).…”