Progesterone secretion during pregnancy and pseudopregnancy in the ferret

In the ferret, pregnancy and pseudopregnancy last 6 weeks. Histological study of the CL and endo-metrium indicates a parallel rate of progestin secretion in the two conditions (Deanesly, 1967) and suggests that the products of conception do not affect CL activity in this species. Further evidence has been sought on this point by assay of the progesterone content of plasma samples collected from pregnant and pseudopregnant ferrets. In the present work, pseudopregnancy was induced by mating so that comparison could be made with the progesterone levels in females rendered pseudopregnant by injection of LH (Blatchley & Donovan, 1972). After this work was completed the results of a similar study were published by Heap & Hammond (1974). Ferrets of the albino and polecat varieties were used. They were kept under a lighting regimen of 16 hr light: 8 hr dark and fed a proprietary diet with water freely available. Animals were inspected at weekly intervals for vulval swelling and when fully in oestrus were paired with a fertile or a vasecto-mized male for 24 hr or injected s.c. with 300 pg LH (NIH-LH-B4). The day of mating or gonado¬ trophin injection was designated Day 0. On Days 1-5, Day 7 and at weekly intervals thereafter, 2 ml blood were collected by cardiac puncture into heparinized syringes under pentobarbitone sodium (Nembutal: Abbott Laboratories) anaesthesia, and the plasma stored at —20°C until assay. Som