Effect of Trypsin on Development of Rana pipiens.

Abstract

Proteases secreted by the embryos of numerous species of fish and amphibia are believed to be important factors in bringing about hatching by digestion of the egg membranes. It has been asserted that in teleosts this protease is much like trypsin and so powerful that it attacks the embryo itself. 1 This statement conflicts with the dictum that living organisms are resistant to digestive enzymes. A striking confirmation of the latter view is Northrup's demonstration of the immunity of a wide variety of organisms to concentrated trypsin. 2

These conflicting statements suggested the desirability of investigating the action of trypsin on the embryologically useful amphibian Rana pipiens. Since this anuran appears to possess a hatching enzyme the effect of trypsin on both membranes and embryonic viability was studied. The eggs were stripped of excess jelly on paper toweling and immersed in a 10% solution of dialyzed trypsin made up in 10% Ringer solution. Each experiment involved 25-50 eggs. Table I gives some typical results.

These results are in agreement with Northrup's work in their clear distinction between the susceptibility of the membrane proteins and the resistance of the living organism to trypsin. The possibility, suggested by work on teleosts, of a general embryonic sensitivity to digestive enzymes is not substantiated. While this may still be the case in teleosts, it seems more likely that the injurious action of the egg contents on the embryos was due to digestion products.

The parallelism between the effects of trypsin and normal hatching in Rana pipicns is in agreement with the theory that normal hatching is due to a digestive enzyme. It should be pointed out in this connection that the power of trypsin to mimic normal hatching makes it useful in large scale chemical work with early stages of anurans where the presence of the difficultly removable membranes may prove a hindrance to analysis or penetration.