Lymphatic Flow Alterations Secondary to Changes in Total Serum Calcium Levels

Abstract

In spite of the numerous investigations directed to stcdy lymph propulsion, wide discrepancy exists about the mechanisms of action of drugs altering thoracic duct lymph flow (1-3). During our previous studies on the transport of calcium by the lymph we observed that between the onset of a hypocalcemic challenge produced by ethylenediaminotetracetate infusion and the return of serum calcium to normal levels, thoracic duct lymph flow (TDLF) was markedly increased (4). Further experiments determined that the rise in serum calcium that followed hypocalcemia was responsible for the increase in TDLF. The purpose of this investigation was that of analyzing and quantifying such a response.Methods and Materials. Experiments were performed in adult mongrel dogs of both sexes divided in groups of five animals each. They were fed achow containing all essential nutrients in their adequate proportions and tap water ad lib. One group of these animals was parathyroidectomized three days prior to the experiment. The success of the ablation was assessed by the fall in total serum calcium. Whole milk was administered ad lib postoteratively to the parathyroidectomized animals to prevent tetany. The amount of milk consumed varied from animal-to-animal but it was helpful in slowing down the general deterioration observed in parathyroidectomized dogs.On the morning of the experiments, dogs were anesthetized with intravenous pentobarbital in successive doses to the point of apnea. This level of anesthesia was maintained throughout the experiment by additional pentobarbital doses in order to avoid changes in respiratory rate, depth ' This work was supported by a grant from The John A.Hartford Foundation, Inc. and rhythm, which can alter TDLF. Animals were intubated with a cuffed endotracheal tube connected to a positive pressure ventilator (Bird). Respiratory rate was regulated to produce a panting-type of respiration (45/min at 15 cm of water of maximum inspiratory pressure). The right femoral artery and vein were dissected at the groin and catheterized with a polyethylene catheter advanced to the abdominal aorta and the inferior vena cava levels, respectively. Pressures were recorded using transducers and a multichannel apparatus.The thoracic duct was exposed over the left side of the neck, ligated at its entrance into the jugular vein and catheterized with a 'polyethylene catheter. Lymph was allowed to flow by gravity into a fraction collector. Lymph flow was expressed as ml of lymph/kg body wdmin. After a period of stabilization during which blood pressure and lymph flow were found to be constant, a bolus dose of a 10% solution of calcium gluconate in water was injected and calculated to provide 0.5 mg of ionic calcium/kg body wt. The same amount of calcium was reinjected when lymphatic flow and aortic blood pressure (A3P) returned to a new steady baseline. In two additional groups of intact and parathyroidectomized animals, a solution of 0.9% sodium chloride in water was injected in volumes equal to those calculated for calcium gluc...