A COMPARISON OF THE INFANTILE AND ADULT RAT METHODS FOR THE ASSAY OF THE OESTRUS-INDUCING GONADOTROPHIC SUBSTANCE

¹ From the Connaught Laboratories, University of Toronto

1. Dose-effect curves have been constructed relating the induction of vaginal oestrus in the 21 day old rat and the dose of gonadotrophic substance administered (a) in a single injection and (b) over a period of 3 days.

2. Subdivision of the dose is necessary with this test object in order to obtain uniform responses.

3. The slope of the regression line for the infantile animal (divided dose) is significantly flatter than that pertaining to the dietary anoestrous adult rat of the same strain. Hence the accuracy of the latter test is greater. When twenty animals receive the standard preparation and twenty receive the preparation being tested, and the response in each case is 50 per cent, the limits of error at P = 0.99 are 65 and 154 per cent for the infantile rat test and 76 and 131 per cent for the adult rat test.

4. The advantages of the adult rat method are discussed.