Distribution of Progesterone Receptors and the Membrane Component of the Progesterone Receptor in Various Organs and Tissues of Male and Female Rats

Progesterone regulates reproductive processes and affects many functions of various non-reproductive organs. Its effects in mammals and humans are mediated by nuclear (nPRs) and membrane progesterone receptors (mPRs). The action of progesterone through different types of receptors differs significantly and also has tissue-specific features. The expression of known types and subtypes of progesterone receptors in tissues of male and female rats has not been sufficiently studied. The aim of this work was to investigate the expression of five mPRs genes and nPRs gene, as well as membrane component of progesterone receptor PGRMC1 in reproductive organs and in 17 non-reproductive tissues of male and female rats by reverse transcription followed by real-time PCR. A high level of nPRs gene expression has been found not only in reproductive organs of female rats (uterus, ovary, mammary glands), but also in seminal vesicles of male rats, in the brain and trachea of both sexes, in blood vessels and in the pancreas of females. The highest level of expression of mPRs genes of all subtypes was in the testes, while expression of the gene encoding nPRs was practically undetectable in them. Expression of genes encoding mPRs was also detected in the liver and spleen of male and female rats, while expression of the gene encoding nPRs was at the background level. No expression of nPRs, mPRs and membrane component of progesterone receptor (PGRMC1) genes was detected in muscle, and its level was very low in heart in animals of both sexes. Nuclear and membrane receptor mRNA expression in non-reproductive tissues in rats has been shown to be sex-dependent. Transcription of nPRs and three subtypes of mPRs (α, β, δ) was predominant in females, and two subtypes of mPRs (γ, ε) were predominant in males. Evidence for the presence of progesterone receptors in tissues not involved in reproduction supports the action of progesterone on these organs. The high mRNA levels of various progesterone receptors in male rat tissues such as pancreas, lung, kidney, and trachea suggest an important physiological role of progestins not only in females but also in males, which is still poorly understood. The paper also discusses the known functions of progesterone receptors in the tissues studied.