PREGNANCY CHANGES IN THE RABBIT'S UTERUS AND THEIR RELATION TO ENDOCRINE ACTIVITY.-II. THE ACTION OF GONADOTROPIC PREPARATIONS OF THE PITUITARY AND OF PREGNANCY URINE

¹ Macaulay Laboratory, Institute of Animal Genetics, University of Edinburgh

Minced bovine anterior pituitary lobe substance, alkaline extracts of the same, and gonadotropic extracts of the urine of pregnant women have been injected into rabbits and the duration of activity of the luteal tissue formed has been determined; progestational proliferation of the endometrium and inhibition of the in vitroreaction to a posterior pituitary lobe extract of the uterine musculature were used as criteria of luteal secretion. A single injection (intramuscular or intravenous) of the above preparations was, as a rule, followed by a period of luteal activity more or less equivalent to the duration of normal pseudopregnancy. Certain exceptions to this type of effect are described.

Repeated injections have prolonged the period of luteal activity; towards the end of this period it has been possible, in a limited number of experiments, to obtain inhibition of the reaction of the uterus to the posterior pituitary lobe extract in the absence of progestational proliferation of the endometrium. The significance of these phenomena is discussed, and it is suggested that they may be explained on the assumption that the corpus luteum secretes two hormones responsible for the progestational and the inhibitory effects respectively.

I wish to express my acknowledgments to Dr B. P. Wiesner for help and advice; and to thank him and Mr R. E. Illingworth for the pituitary and pregnancy urine extracts used.