VILLUS AND CRYPT CELL COMPOSITION IN THE SECRETING MOUSE JEJUNUM MEASURED WITH X-RAY-MICROANALYSIS

The response of the villus and crypt cells of the mouse jejunum to sec retagogues has been assessed through measurements of cellular composit ion with x-ray microanalysis. In nonstimulated tissues the Na concentr ation ([Na]c) of the crypt cells was significantly less, and the K ([K ]c) and Cl ([Cl]c) concentrations were significantly greater, than tha t of the villus cells. There was also a decreasing gradient of [Na]c a nd increasing gradient of [K]c from the villus tip to crypt base due t o a greater number of cells with a high [Na]c and low [K]c in the uppe r regions of the villi. Theophylline (10 mmol L-1) stimulated a sustai ned increase in bumetanide sensitive short circuit current (Isc) and s ignificantly decreased the [Na]c of the villus cells. Similar, but sma ller changes were seen in the crypt cells. Changes in villus cell [Na] c reflected a reduction in the number of cells with a high [Na]c. Inhi bition of the apical Na/H exchanger (1 mmol L-1 amiloride) had little effect on basal Isc and the subsequent addition of theophylline increa sed Isc to a comparable extent as seen without amiloride. However, aft er amiloride treatment the only change in cellular composition was a r eduction in the [Cl]c of both crypt and villus cells, suggesting that both regions are involved in the secretory response. These data sugges t that the dominant response of the jejunum to secretagogues is an inh ibition of Na absorption via Na/H exchange in the villi and the secret ory response is distributed throughout the crypt/villus axis.