To: All students in PMCOL 3A06

From: P.K. Rangachari

Re: Comments on the End of Term TRIPSE

The problem dealt with the antagonistic effects of component(s) in Red Huron Wine (RHW) against phenylephrine induced contractions of rat aortic smooth muscle.

The essential points that needed to be explained were the following:

(1) The antagonism is seen when RHW is added either after or before PE.

(2) The antagonism is unsurmountable at the concentration shown. There is a clear decrease in the maximal response.

(3) The response elicited is clearly dependent on the presence of the endothelium.

(4) The effect is seen with red wines but not white wines.

There are many possible explanations; however it was important that at least the first three points should be covered. IF anyone included a possible explanation for the 4th item, they received bonus marks.

As a general comment, it appeared that several of you focused on the presence of an antagonist in RHW. This was acceptable, though the suggestion that a Schild analysis would help dissect out the mechanism was clearly wrong, since the data presented suggested that the competition was unsurmountable. Again, several of you missed the significance of the endothelium-dependence.