Bollman, Jesse L.

The total amount of I131-containing compounds excreted in the urine of the dehepatized dog receiving either radioactive thyroxine or triiodothyronine is similar to that of the normal dog receiving similar injections. The important role of the liver in the deiodination of thyroxine and triiodothyronine is indicated by the failure of the liverless animal to convert these compounds to inorganic iodide as completely as does the normal dog. Only a small percentage of the I131 compounds excreted by the liverless dog appears as inorganic iodide. The most abundant iodine compound in the urine of the dehepatized dog is a conjugate of thyroxine when thyroxine is injected, and an unidentified compound, b, when triiodothyronine is injected.

Lymphocytes, obtained from the intestinal lymph of rats and labeled with radiochromium or radiophosphate, were injected intravenously into rats. Both autogenous and homologous lymphocytes which were motile at the time of injection were used. No appreciable radioactivity became evident in the intestinal lymph until 4 hours after injection, but as much as half of the injected material was recovered in the lymph of the subsequent 24 hours. All the radioactivity disappeared from the blood within a half-hour, and began to reappear within 4 hours to reach maximal activity at about 24 hours. Tissue distribution determined at intervals indicated that 73% of the injected material was in the spleen at one-half hour, and that there was a gradual decrease to 7% by 72 hours. The content in bone marrow decreased from 4.5 to 1.3% at the same time. The thymus gland, lymph nodes, liver and small intestine showed increases over this same period. An active migratory process of lymphocytes is clearly indicated.

Urinary-excretion and fecal-recovery methods were employed in the study of intestinal absorption of cobalt60-labeled vitamin B12 in the normal male albino rat. a) The logarithm of the fecal excretion, as well as of the urinary excretion augmented by an intraperitoneal flushing dose of unlabeled vitamin, increased linearly with the logarithm of the oral dose. This same relation of fecal excretion to oral dose is also apparently true in man. b) Increasing the intraperitoneal flushing dose over a wide range brought about a progressive increase in the percentage of the labeled oral dose excreted in the urine, but this increase was of small magnitude. c) The optimal time for administration of the intraperitoneal flushing dose in the rat appeared to be about 2 hours after administration of the labeled oral dose. d) The male albino rat seems to be an excellent experimental animal for use in the study of vitamin B12 absorption.

Dogs excreted the same compounds in the urine after injections of radioactive thyroxine whether they were normal or had a biliary fistula or biliary obstruction. Dogs with biliary fistulas excreted more of the conjugate in the urine than did normal dogs. Dogs with biliary obstruction excreted the largest amounts of the conjugate and also showed increased levels of the conjugate in the blood. All the changes were minor, however, compared to those found after hepatectomy. No evidence was found for conversion of thyroxine to triiodothyronine or tetraiodothyroacetic acid, but the present studies would not exclude the possibility that these substances are rapidly transformed intermediates in the metabolism of thyroxine.

Observation of the hilar lymphatics from 100 canine livers seen at operation disclosed two drainage pathways: 1) a main hilar system, draining predominantly the right lobes and 2) an accessory hilar system, draining mainly the left lobe. In 94% of the animals all of the hilar lymph seemed to pass into one common efferent trunk which then discharged it into the cisterna chyli. Apparently, 69% of the animals had a lymph vessel large enough to permit cannulation for physiologic studies. From a study of five dogs in which the gallbladder was removed and the common bile duct ligated and in which there were fistulas of both the hilar lymph trunk and the thoracic duct, it was concluded that, normally, about 80% of the lymph leaving the canine liver probably travels by the hilar route and the remaining 20% by the hepatic venous lymph route. The mean flow of hilar lymph from the liver during biliary obstruction in 20 unanesthetized animals was 0.66 ml/kg body weight/hr., the standard error of the mean being ±0.07.

Total fatty-acid output in the intestinal lymph in rats and in the thoracic-duct lymph in dogs was studied during fasting and during a fat-free diet period. Daily total fatty-acid output in the intestinal lymph was found to be fairly constant during fasting or when the rat was fed a fat-free diet. There is an inverse relationship between total fatty-acid concentration and the volume of intestinal lymph. In the absence of pancreatic juice or of both bile and pancreatic juice, the total fatty-acid output in the thoracic-duct lymph in dogs was decreased to one-third or one-fourth that of the normal dog. The endogenous lipid metabolism of the intestine is discussed in relation to steatorrhea.

The content of either D2O or Na24 has been measured in the intestinal lymph, portal venous blood, and femoral arterial blood of unanesthetized hydrated rats after administration of the isotope into the stomach, duodenum, or peripheral or portal vein. Little, if any, water or sodium ion is delivered to the body by a lymphatic pathway after absorption from the small intestine. At least 99% is carried in portal venous blood. The amount of isotope found in intestinal lymph was proportional to lymph volume whatever the route of administration, and derived mainly from the arterial blood. Even during absorption of water or sodium ion from the small intestine the arterial circulation is the principal source of the water and sodium of the lymph.