Changes in Vascular and Extravascular Volumes of Eel Muscle in Response to Catecholamines: The Function of the Caudal Lymphatic Heart

Abstract

Vascular volume changes in an isolated saline-perfused eel tail preparation in response to catecholamines were small (< 2 %) and are explicable in terms of changes in volume of pre-capillary resistance vessels. Extravascular-extracellular (interstitial) volume increased less than 3 % during infusion of adrenaline (AD) at concentrations of 1 × 10⁻⁶ to 1 × 10⁻³ M. Injection of doses of AD and noradrenaline (NA) between 1 nmol and 100 nmol caused maximum interstitial volume changes of less than 11%. Isoprénaline caused only very small changes in vascular and interstitial volumes. Caudal lymph heart frequency increased when high concentrations (> 1 × 10⁻⁶ M) and doses (> 1 nmol) of AD and NA were administered. Caudal lymph heart frequency increases were significantly correlated with changes in outflow after vascular volume adjustments. One function of the caudal lymph heart is to return interstitial fluid to the vascular system.