No abstract

Puerarin (daidzein-8-C-glucoside) is the major bioactive isoflavone of kudzu root (the root of Pueraria lobata). Its metabolic fate, however, is not well-known. In this study, a sensitive and specific LC-ESI-MS/MS method for the determination of puerarin and its metabolites daidzein, dihydrodaidzein, and equol was developed for their analysis in biological samples. Two new metabolites of puerarin, mono- and dihydroxylated derivatives, were detected in the urine and feces of rats after oral administration. The persistence of puerarin in blood and urine as the principal metabolic form for the period of 4-72 h after oral administration suggested that puerarin is rapidly absorbed from the intestine without metabolism. Its presence in organs such as the brain suggests that this glucoside may enter tissues by specific transport pathways. Study of these metabolites may provide further understanding of the health beneficial effects of puerarin in kudzu dietary supplements.

Permeabilized intestinal absorptive cell brush borders contain a perijunctional ring of actin and myosin (PAMR) that can be induced to contract. Recently, morphological changes suggestive of PAMR contraction were shown to occur in absorptive cells of ileal epithelium after exposure to cytochalasin D (CD) (J. Cell Biol. 102: 2125-2136, 1986). With this response, altered tight junction structure and enhanced tight junction permeability also occur. To further assess the relationship between PAMR contraction and enhanced tight junction permeability, we examined the effect of the uncoupler 2,4-dinitrophenol (DNP) on this CD response. Progressive depletion of functionally defined intraepithelial energy stores occurred with DNP concentrations of 0.1-1 mM. Such DNP concentrations did not independently impair tight junction barrier function. Depletion of energy stores before CD exposure ablated the ability of CD to induce abnormalities of tight junction permeability. Similarly, PAMR condensation and alterations in tight junction structure could be dissociated from CD exposure by prior depletion of functional energy reserves. These data tie CD elicited alterations in tight junction structure and permeability to an energy dependent event that appears to be PAMR contraction. We speculate that tensile forces within the PAMR regulate tight junction structure and function.

A highly reproducible in vitro model of intestinal epithelial injury in guinea pig ileum was used to study the structural and functional events that accompany rapid epithelial repair. This model is characterized by denudation of the villus tip followed by rapid restitution of the epithelial barrier. Using standard electrophysiological and quantitative morphometric techniques, we found that immediately after injury the number of cells lost exceeded the number of empty cell positions on the denuded basement membrane by 100%. Concurrently, cytoplasmic processes of subepithelial myofibroblasts contained condensations of microfilaments that were not apparent in controls. Additionally, villus height was diminished immediately after injury, and progressively decreased during the restitution period. In tissues that were depleted of ATP using the uncoupler dinitrophenol and in tissues functionally denervated by tetrodotoxin, villus shortening after injury was significantly reduced. Denervation also retarded functionally and structurally defined reestablishment of epithelial barrier function. These data suggest that intestinal epithelial repair is aided by energy-dependent, neurally mediated villus contraction. We speculate that the subepithelial network of myofibroblasts is responsible for this process, which effectively minimizes the denuded surface area to be reepithelialized.