Transfected D2 dopamine receptors mediate the potentiation of arachidonic acid release in Chinese hamster ovary cells.

A rat D2L dopamine receptor, a splice variant of the D2 receptor, has recently been cloned. When transfected into and stably expressed in Chinese hamster ovary cells, these receptors mediate the inhibition of both basal and forskolin-stimulated cAMP production, as previously described. We examined what role this receptor might play in the production of the second messenger arachidonic acid. The calcium ionophore A23187 stimulated the release of arachidonic acid, and this release of arachidonic acid was potentiated by dopamine in a concentration-dependent manner. Dopamine alone, however, had no effect on arachidonic acid release. Quinpirole, a D2-selective agonist, augmented A23187-stimulated arachidonic acid release, and sulpiride, a D2-selective antagonist, blocked this augmentation. cAMP analogs and agents that activate adenylyl cyclase were utilized in an attempt to overcome this dopamine effect. Forskolin, prostaglandin E2, dibutyryl-cAMP, 8-(4-chlorophenylthio)-cAMP, and pertussis toxin all had no appreciable effect on either A23187-stimulated arachidonic acid release or the dopamine enhancement. Inhibition of protein kinase C using long term phorbol ester desensitization and pharmacological inhibitors diminished the dopamine potentiation of arachidonic acid release. These results suggest that the D2 receptor may be increasing the release of arachidonic acid by a mechanism involving protein kinase C but independent of the D2 receptor's inhibition of adenylyl cyclase.     

Pediatric barium enema examination: Optimizing patient selection with univariate and multivariate analyses

We prospectively evaluated a total of nineteen symptoms, signs, and laboratory findings in 471 of 557 consecutive pediatric patients (from newborn to age 17) referred for barium enema examinations, to determine predictors of an abnormal study. A univariate analysis was performed, and a logistic regression model was developed. The most frequent indicators for the barium enema examinations were abdominal pain (48%), constipation (27%) and tenderness (25%). Twenty-two percent of the examination were abnormal, and the most common diagnoses were intussusception (n=22), appendicitis (n=17), infectious colitis (n=15), and Hirschsprung disease (n=14). The indicators that were most helpful to predict a barium enema abnormality were abdominal mass, leukocytosis, guaiac-positive stools, diarrhea, anemia, tenderness, and age less than 1 year. If barium enema examinations were performed only when at least one of the predictive indicators was present, 29% of examinations would be eliminated, and 4.8% of patients with detectable disease would be missed. The data indicate that identification of certain clinical variables can provide an effective initial strategy for selecting patients to undergo barium enema examinations.