Plasma progesterone levels before and at the time of implantation in the ferret

Abstract

Two recent reports of plasma progesterone levels during early pregnancy in the ferret show significant differences during and immediately before implantation. Heap & Hammond (1974) found peak progesterone levels on Day 12 while Blatchley & Donovan (1976) recorded a maximal level on Day 14 that was approximately half that reported by Heap & Hammond (1974) for the same day using the same technique (radioimmunoassay). Heap & Hammond also measured progesterone by fluorometric and competitive protein-binding assays and found levels 2–3 times higher than did Blatchley & Donovan. In this paper I report an attempt to resolve this difference.