Until recently, the corpus luteum (CL) was considered to be the main source of progesterone (P4) during pregnancy in the domestic cat (Felis catus). However, other possible sources of P4 have not been ruled out. Although feline placental homogenates were found to be capable of synthesizing P4, expression of the respective steroidogenic enzymes has not been investigated at the molecular level. Therefore, in the present study, expression of the two major factors involved in the synthesis of P4 - 3beta-hydroxysteroid dehydrogenase (3betaHSD) and steroidogenic acute regulatory protein (StAR) - was investigated in the feline CL and placenta during the course of pseudopregnancy and pregnancy.

The aim of the study was to characterize endometrial mRNA transcription, immunolocalization, and protein expression of interleukin (IL) 1alpha, IL1beta, IL6, and IL1RI, IL1RII, and IL6Ralpha/beta in the course of endometrosis during the estrous cycle. Additionally, the influence of IL1alpha, IL1beta, and IL6 on prostaglandin (PG) secretion and PG synthase mRNA transcription in endometrial tissue during endometrosis was investigated. The endometrial samples were obtained at the early (n = 12), mid- (n = 12), and late (n = 12) luteal phases and at the follicular (n = 12) phase of the estrous cycle. Within each of these phases, there were four samples within each category I, II, and III of endometrium, according to the Kenney classification. In experiment 1, transcription of IL1alpha, IL1beta, IL6, and their receptor's (IL1RI, IL1RII, and IL6Ralpha/beta) mRNAs and their immunolocalization and protein expression were determined using real-time PCR and immunohistochemistry, respectively. In Experiment 2, endometrial samples (n = 5 samples within categories I, II, and III) were obtained for tissue culture in the midluteal phase of the estrous cycle. The endometrial tissues were stimulated with IL1alpha (10 ng/ml), IL1beta (10 ng/ml), IL6 (10 ng/ml), and oxytocin (positive control; 10⁻⁷ M) for 24 h. The PG concentration was determined using ELISA. In addition, transcription of PTGS-2, PGES, and PGFS mRNAs was determined using real-time PCR. ILs were found to regulate PG secretion via modulation of PG synthases in equine endometrium. The alterations in IL and the expression of their receptors, and in endometrial secretory functions, were observed during the course of endometrosis, and suggest serious changes in the endometrial microenvironment. The described disturbances may be closely related to impaired endometrial processes responsible for the subfertility or the infertility in endometrosis.