Effect of Somatostatin on the Flow Rate and Triglyceride Levels of Thoracic Duct Lymph In Normal and Vagotomized Dogs

The role of circulating somatostatin (SRIF) in triglyceride (TG) homeostasis was evaluated in fasting and postprandial lymph of the canine thoracic duct. Cyclic SRIF at a very low, near physiologic (50 ng/min), and pharmacologic (5 μg/min) doses was infused into the portal or the femoral vein, and lymph was collected every 10 min through a cannula inserted into the duct under neuroleptanalgesia. The intraportal (IP) and intrafemoral (IF) SRIF infusion, but not saline infusions, significantly and almost identically reduced the rates of fasting lymph flow to levels of 87% and 91% of the preinfusion values, respectively, at a dose of 50 ng/min, and to 78% and 80%, respectively, at both rates at a dose of 5 μg/min. The attenuating effect of the IP and IF SRIF infusions at both rates upon lymph flow was completely abolished by vagotomy at the diaphragmatic level. The flow rate, TG concentration, and TG content (flow × concentration) of lymph obtained 3 h after a fat- and protein-rich meal ingestion were significantly and almost identically reduced during the IP and IF SRIF infusions at 50 ng/min, but not during saline infusions. Greater attenuation of these parameters was observed with 5 μg/min infusions, regardless of the route of administration. These results indicate that SRIF in near physiologic as well as pharmacologic doses can inhibit lymph flow after traversing the liver in the presence of the vagus nerve. They suggest the the other splanchnic organs may have a physiologic influence upon TG entry from the gut through alterations of dynamics of the splanchnic lymph system.