Gallbladder mechanics in newborn piglets

Effect of ursodeoxycholic acid on inflammatory infiltrate in gallbladder muscle of cholesterol gallstone patients

BACKGROUND

Reduced gallbladder (GB) contractility and chronic inflammatory changes in the mucosa have been reported in patients with cholesterol gallstones (GS). Ursodeoxycholic acid (UDCA) restores GB contractility and antagonises liver macrophage activation. In the colon, hydrophobic bile acid, not hydrophilic UDCA, induces mast cell degranulation. We studied the presence of monocyte/macrophage infiltrate, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) expression, the number of total and degranulated mast cells in the GB muscle layer of cholesterol GS patients, and the effect of UDCA administration.

METHODS

Gallbladder tissue was obtained from cholesterol GS patients, either treated or untreated with UDCA (10 mg kg(-1) day(-1)) for 30 days prior to surgery. Gallbladders removed for neoplastic diseases, not involving GB, were evaluated for control purposes. The presence of monocytes/macrophages (CD68 positive), granulocytes, and mast cells, and the COX-2 and iNOS expression, was determined immunohistochemically.

KEY RESULTS

The number of CD68, granulocytes, mast cells, COX-2 and iNOS positive cells was significantly higher in the muscle layer of GS patients than in controls. Compared to untreated patients, those treated with UDCA showed significantly lower levels of CD68, COX-2 positive cells and degranulated mast cells and a lesser number of iNOS positive cells and granulocytes.

CONCLUSIONS & INFERENCES

An inflammatory monocyte/macrophage, mast cell and granulocyte infiltrate is present in the GB muscle layer of GS patients. Ursodeoxycholic acid decreases macrophages, degranulated mast cells and COX-2 expression. These results suggest that monocytes/macrophages and degranulating mast cells contribute to muscle cell dysfunction in cholesterol GS patients and support the anti-inflammatory effect of UDCA.

Molecular basis of neonatal cholestasis

At present, specific evidence regarding the molecular mechanisms of neonatal cholestasis is limited. The recent explosion in the understanding of the molecular physiology of bile formation has been fueled by the discovery of several genes that are involved in familial cholestasis. The ever-growing understanding of the functional immaturity of the neonatal liver is sure to be enhanced by the study of the ontogeny of important hepatobiliary transporters as they are discovered. The understanding of the functional differences between the immature and mature liver is key to the understanding of neonatal cholestasis.

Actions of histamine on muscle and ganglia of the guinea pig gallbladder

Histamine is an inflammatory mediator present in mast cells, which are abundant in the wall of the gallbladder. We examined the electrical properties of gallbladder smooth muscle and nerve associated with histamine-induced changes in gallbladder tone. Recordings were made from gallbladder smooth muscle and neurons, and responses to histamine and receptor subtype-specific compounds were tested. Histamine application to intact smooth muscle produced a concentration-dependent membrane depolarization and increased excitability. In the presence of the H(2) antagonist ranitidine, the response to histamine was potentiated. Activation of H(2) receptors caused membrane hyperpolarization and elimination of spontaneous action potentials. The H(2) response was attenuated by the ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide in intact and isolated smooth muscle. Histamine had no effect on the resting membrane potential or excitability of gallbladder neurons. Furthermore, neither histamine nor the H(3) agonist R-alpha-methylhistamine altered the amplitude of the fast excitatory postsynaptic potential in gallbladder ganglia. The mast cell degranulator compound 48/80 caused a smooth muscle depolarization that was inhibited by the H(1) antagonist mepyramine, indicating that histamine released from mast cells can activate gallbladder smooth muscle. In conclusion, histamine released from mast cells can act on gallbladder smooth muscle, but not in ganglia. The depolarization and associated contraction of gallbladder smooth muscle represent the net effect of activation of both H(1) (excitatory) and H(2) (inhibitory) receptors, with the H(2) receptor-mediated response involving the activation of K(ATP) channels.

Gallbladder distention in premature neonates receiving parenteral nutrition

Contraction of the gallbladder is mediated through the release of cholecystokinin from duodenal cells secondary to enteral feedings. Premature infants are often nourished by parenteral hyperalimentation leading to prolonged inactivation of the gallbladder. Such inactivation probably accounts for the increased incidence of gallbladder distention observed in premature neonates. Two cases of premature infants are described in whom distention of the gallbladder occurred during parenteral hyperalimentation. The distention resolved spontaneously secondary to the introduction of enteral feedings. A trial period of oral or tube feeding is recommended in such cases prior to any attempt to release the distention by a surgical intervention.