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Patterns in the Puzzle

Pierre is perplexed by the results he has been getting. He has been studying the effects of prostaglandins on the transport properties of the canine proximal colon.

The intestinal lining devoid of the muscle layers is set up in Ussing chambers. This procedure allows the vectorial properties to be preserved. The tissue is set up between two halves of Lucite chambers so that the serosal and luminal solutions can be independently altered. The solutions on either side have the same composition (regular PSS) and are continuously bubbled with 95% O2 / 5% CO2 to maintain a pH of 7.4. The short-circuit currents (Isc) have been used to monitor tissue responsiveness. Earlier studies had shown that in this tissue increases in Isc reflected Cl secretion (i.e net movement of Cl from the serosal to luminal solutions).

The addition of one particular prostaglandin (PGD2) to the serosal solutions produces changes in Isc. Three different patterns are seen . These reflect between animal rather than within animal variations, since the patterns are quite consistent between multiple pieces set up from the same animal. The frequencies were as follows: Pattern 1 (8 out of 18 animals); Pattern 2 (7 out of 18); Pattern 3 (3 out of 18).

PGE2, the isomer of PGD2, produces only increases in Isc, no decreases being noted.


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