X-ray microanalysis of rotavirus-infected mouse intestine: a new concept of diarrhoeal secretion
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A J Spencer1, M P Osborne, S J Haddon
1Department of Physiology, University of Birmingham, England.
Abstract:
Neonatal mice were infected at 7 days of age with rotavirus [epizootic diarrhea of infant mice (EDIM) virus] and killed at 24-h intervals postinfection (PI). Cytoplasmic concentrations of Na, Mg, P, S, Cl, K, and Ca intestinal epithelial cells from infected and age-matched control animals were measured by x-ray microanalysis. In villus tip cells, Ca concentration increased at 24-96 h PI; Na concentration increased at 24-72 h PI; Ca and Na concentrations were near normal by 168 h PI. K concentration decreased 24-72 h PI, and Cl concentration decreased 48-96 h PI. In crypt cells, changes were observed without a discernible pattern: at 96 h PI, Na, Mg, S, and Cl concentrations increased and K concentration decreased; at 120 h PI, the concentrations of all elements except Na and Ca increased. In villus base cells, the mean concentrations of all elements except Ca peaked at 48-72 h PI and at 120 h PI. Na and Cl concentrations increased dramatically in some cells from 48 h PI onward. All the above concentration values were obtained from freeze-dried specimens and expressed in millimoles per kilogram of dry weight. Conversion of a limited number of data, pertaining to villus base cells, from dry weight to wet weight was possible. This conversion revealed that villus base cells in infected animals were more hydrated than corresponding cells from control animals. Also, the Na and Cl concentrations in mmol/kg H2O were significantly higher in villus base cells from infected animals than in those from corresponding controls: 137 +/- 7 versus 38 +/- 4 (Na) and 121 +/- 5 versus 89 +/- 6 (Cl). Wet weight concentrations of other elements were either the same (Mg) or lower (P, S, and K) after infection with virus. From these studies, a new concept of the pathophysiology of rotavirus-induced diarrhoeal secretion is proposed: stimulation of villus base cells to rapid cell division is accompanied by transient accumulation of Na and Cl; excess NaCl is secreted into the lumen, which is the driving force for fluid loss.
Insights
Rotavirus infection in neonatal mice causes significant changes in intestinal epithelial cell ion concentrations, leading to increased hydration and ion secretion, driving diarrheal fluid loss.
Area of Science:
- Gastroenterology
- Virology
- Cell Biology
Background:
- Rotavirus, specifically the epizootic diarrhea of infant mice (EDIM) virus, is a common cause of diarrhea in neonates.
- Understanding the cellular mechanisms of rotavirus-induced diarrhea is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the changes in intracellular ion concentrations in intestinal epithelial cells of neonatal mice infected with rotavirus.
- To elucidate the role of ion transport in the pathophysiology of rotavirus-induced diarrhea.
Main Methods:
- Neonatal mice were infected with EDIM virus and samples were collected at 24-hour intervals post-infection.
- X-ray microanalysis was used to measure cytoplasmic concentrations of Na, Mg, P, S, Cl, K, and Ca in intestinal epithelial cells.
- Ion concentrations were measured in villus tip, crypt, and villus base cells.
Main Results:
- Rotavirus infection altered ion concentrations in all measured cell types, with notable increases in Na and Ca in villus tip cells and significant increases in Na and Cl in villus base cells.
- Villus base cells in infected mice showed increased hydration and significantly higher wet weight concentrations of Na and Cl compared to controls.
- A new concept proposes that stimulated villus base cell division leads to Na and Cl accumulation and subsequent secretion, driving fluid loss.
Conclusions:
- Rotavirus infection disrupts normal ion homeostasis in intestinal epithelial cells.
- Increased Na and Cl accumulation and secretion by villus base cells play a key role in rotavirus-induced diarrheal fluid loss.
- These findings offer a new perspective on the pathophysiology of rotavirus diarrhea.