The PBR is a mitochondrial protein composed of at least two subunits, an approximately 30-kDa subunit that contains the site for BZs and an approximately 18-kDa subunit that binds isoquinoline carboxamide derivatives. Porphyrins and diazepam binding inhibitor are putative endogenous ligands for these receptors, which are under neural and hormonal control. Alterations in the density of PBR seem to be a sensitive indicator of stress: up-regulation after acute stress and down-regulation induced by repeated stress. PBR-specific ligands are involved in the control of cell proliferation and differentiation, and their binding is increased in some cancer tumors. Numerous studies in various endocrine organs have revealed that PBR are located in specific regions or tissues in the organs. Furthermore, PBR densities in various organs subject to hormonal control are regulated by organotropic hormones. At least in some cases, BZ ligands do not exert a specific effect in an organ, but rather modulate the well-documented effects of that particular hormone. To the best of our knowledge, BZ ligand action in peripheral tissues is dependent on recognition of PBR, which may suggest a receptor-mediated action.

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The administration of hCG to women undergoing in vitro fertilization and embryo transfer (IVF/ET) results in the meiotic maturation of cumulus-oocyte complexes (COC). Sometimes oocytes being aspirated for IVF/ET fail to resume meiosis in vivo and even after a subsequent 20-h incubation in vitro and are thus defined as meiotic competence failure (MCF) oocytes. The relationship between the proportion of MCF oocytes and other IVF/ET outcomes was studied over 3 years in 703 tested cycles of 487 women. Women yielding one or more MCF oocytes in at least one menstrual cycle represented 8.6% of this population and were defined as MCF women. Cumulus state in the MCF oocyte population was characterized as mature in 57.4 +/- 6.7%, intermediate in 13.9 +/- 4.0%, immature in 24.1 +/- 8.7%, and atretic in 4.6 +/- 2.7%. These values differed significantly, by 0.6-, 2.9-, 7.1-, and 4.6-fold, respectively, as compared to the corresponding COC aspirated from women yielding only meiotically competent (MC) oocytes. In a menstrual cycle yielding both MC and MCF oocytes, the IVF/ET variables were evaluated in the MC oocytes. Thus, in such cases the incidence of fertilization or cleavage and the number of blastomeres per embryo were significantly reduced concomitant with the increase in percentage of MCF oocytes. When the percentage of MCF oocytes was 25% or more, no pregnancy was achieved. Various follicular parameters and serum 17 beta-estradiol (E2) and progesterone (P4) levels were compared in MC and MCF women over the four days preceding day of aspiration.(ABSTRACT TRUNCATED AT 250 WORDS)