The liver plays a central role in the digestion, metabolism, and storage of nutrients. A deficiency of nutrients is often associated with liver disease and may be caused by decreased intake, decreased absorption, decreased storage, abnormalities in metabolism, or the increased requirements for nutrients. Alcoholism is a frequent cause of both malnutrition and liver disease, but nutritional deficiencies are also common in liver diseases not associated with alcoholism.

This is a review of current information concerning the role of hormones and the autonomic nervous system in the control of exocrine secretions of the pancreas. A greater emphasis has been placed on the role of hormones because of information accumulated during the last several years. With the development of radioimmunoassay techniques, it is now possible to correlate circulating hormone concentrations with biological function. The role of hormones has been discussed with the framework of the secretin-glucagon family, the cholecystokinin-gastrin family, and other proposed gastrointestinal hormones and related peptides. Gastrin, secretin and cholecystokinin-pancreozymin are three prime gut hormones that regulate pancreatic secretion. Other hormones that may have a role in pancreatic secretion include glucagon, vasoactive intestinal polypeptide, chymodenin, somatostatin, pancreatic polypeptide, motilin, and bombesin. Neural mechanisms play an important although not so succinct a role in the over-all control of exocrine secretion. A complex relationship exists between the parasympathetic nervous system and the release of the hormones and their effect on pancreatic acinar and duct cells.

The hepatic circulation is reviewed with emphasis on the role of hepatic blood vessels in hepatic and homeostatic functions. Contrasts are made with resistance, capacitance, and fluid exchange functions in other better known vascular beds. Hemodynamic changes that produce shifts in fluid exchange in other tissues are without effect in the liver. Elevations of hepatic venous pressure are transferred quantitatively to the sinusoids and result in prolonged, massive fluid filtration into the abdominal cavity. Other factors that are involved with control of fluid exchange are discussed. The liver contains a large volume of blood which can be rapidly mobilized during hemorrhage. The hepatic circulation is highly sensitive to changes in circulating blood volume and serves as a major buffer for expanded or contracted blood volume. Control of hepatic blood flow and the reciprocal relationship between portal and hepatic arterial flow is discussed. Changes in hepatic blood flow produce marked changes in hepatic clearance rates of a wide variety of compounds. It is concluded that the hepatic artery is not controlled by local tissue metabolism but rather is controlled by an, as yet unknown, mechanism that tends to maintain hepatic blood flow (and therefore clearance rates) constant.

In the search for gastric ATPases that might be related to the mechanism of HCl secretion, an interesting and rather unique K+-stimulated ATPase has been discovered. This enzyme is isolated from oxyntic cells and has been associated with the apical plasma membrane and/or tubulovesicular system. Membrane vesicles containing the K+-stimulated ATPase transport H+ into the vesicular lumen under the appropriate conditions of ATP, Mg2+, and KCl. This process can be measured by pH electrode, binding of certain metachromatic dyes to "energized" sites, or accumulation ratios of substances with appropriate pK values. Vesicular interior can be acidified to pH 3.5 or below. At the present time, it is difficult to distinguish between an electrogenic H+ pump and an electroneutral H+/K+ exchange mechanism. A hypothetical scheme for the gastric H+ secretory mechanism is proposed which fits much of the data from studies on the K+-ATPase, vesicular transport, and intact gastric mucosa.

Based on the current experimental evidence, a model is proposed for mutual interactions of histamine, prostaglandins, and cyclic AMP in regulation of gastric secretion and pathogenesis of peptic ulcer. Histamine acting on H2-receptor-associated adenylate cyclase stimulates cyclic AMP formation and consequently secretion of hydrochloric acid in oxyntic cells. Prostaglandins (mainly E type) in another cell population stimulate cyclic AMP formation which may lead to formation of glycosaminoglycans and glycoproteins. Glycosaminoglycans and glycoproteins may have antisecretory and cytoprotective properties. In addition to this effect, prostaglandin endoperoxides may inhibit histamine-stimulated cyclic AMP formation in oxyntic cells.

The familial aggregation of peptic ulcer disease has been well established, as has its association with such clear-cut genetic factors as blood group O and nonsecretor status. However, the genetics of this disorder, or group of disorders, is still in question. Polygenic inheritance is the prevailing hypothesis that has been proposed for peptic ulcer. This hypothesis was based primarily on the exclusion of a simple mode of inheritance for all ulcer disease. Genetic heterogeneity is an alternative hypothesis that can explain both the familial aggregation of peptic ulcer disease and the lack of a simple Mendelian pattern of inheritance. The evidence for genetic heterogeneity in peptic ulcer disease is reviewed, and studies are proposed to test this hypothesis.

Pigment gallstones are defined as any dark brown-to-black stone, consisting of calcium salts of bilirubin, phosphate, carbonate and other anions, and can be separated into carbonate- and noncarbonate-containing groups. Pigment stones predominate in the rural Orient, in cirrhosis, and in elderly United States patients undergoing cholecystectomy. Clinical associations include bile duct obstruction, stasis, and possibly hemolysis. Of pigment stones, 50% are radioopaque and account for two-thirds of all opaque stones. The concentrations of bile salts, phospholipids,, cholesterol, and total bilirubin in bile are similar to normal levels, but the concentration of unconjugated bilirubin is increased in the bile of some patients. Increased unconjugated bilirubin in bile may be caused by increased hydrolysis of excreted conjugated bilirubin. Unconjugated bilirubin is solubilized by bile salts, but the interaction is primarily nonmicellar. Ionized calcium and pH are important determinants of solubility. Sulfated glycoproteins, excreted in increased amounts in patients with cholelithiasis, may be the site of pigment stone precipitation because these compounds bind calcium salts tightly. E coli is frequently cultured from pigment stones in Japan but not in the United States; thus, bacterial beta-glucuronidase may be important in stone formation in Japan but probably not in the West. Stasis leads to increased calcium secretion and to increases in the concentration of sparingly soluble compounds that may then precipitate. Incomplete emptying of the gallbladder may result in the same concentration process. Unsaturated fats and chronic vagal stimulation cause pigment stone formation in animals. At present, surgery is the only treatment for pigment lithiasis.