Uterine uptake of alpha 2-macroglobulin and alpha 1-proteinase inhibitor from the blood during early implantation in the mouse.

The objective of this study was to investigate the uterine uptake of plasma alpha 1-proteinase inhibitor (53,000 Da) and alpha 2-macroglobulin (725,000 Da) from the blood during implantation in the mouse using isotopic methods. The uterine uptake of albumin (67,000 Da) and immunoglobulin G (150,000 Da) were also measured for comparison. Rates of uptake were assessed from permeability-surface area products estimated from the rate at which the tissue volume of distribution approaches its steady-state value. The permeability-surface area product estimates at implantation sites were 13.3 and 54.8 ml/100 g.h for alpha 2-macroglobulin and alpha 1-proteinase inhibitor, respectively. Given the circulating levels of these proteins in mice, these results demonstrate that considerable amounts of plasma proteinase inhibitors are extravasated into the interstitium in the vicinity of the implanting blastocyst. The permeability-surface area products of all the proteins studied, except immunoglobulin G, were greater at implantation compared to non-implantation sites, confirming greater vascular permeability to plasma proteins at implantation sites compared to non-implantation sites. Estimates of the permeability-surface area products of the studied proteins showed that the uterine vasculature was generally more permeable to proteins with a small than with a large molecular size. Nevertheless, the ratio of the permeability-surface area product between implantation and non-implantation sites for the proteins ranged from 1.1 to 2.9 with no obvious relationship to molecular size.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biochemical and structural insights into mesotrypsin: an unusual human trypsin

Thirty five years ago mesotrypsin was first isolated from the human pancreas. It was described as a minor trypsin isoform with the remarkable property of near total resistance to biological trypsin inhibitors. Another unusual feature of mesotrypsin was discovered later, when it was found that mesotrypsin has defective affinity toward many protein substrates of other trypsins. As the younger sibling of the two major trypsins secreted by the pancreas, cationic and the anionic trypsin, it has been speculated to represent an evolutionary waste with no apparent function. We know now that mesotrypsin is functionally very different from the other trypsins, with novel substrate specificity that hints at distinct physiological functions. Recently, evidence has begun to emerge implicating mesotrypsin in direct involvement in cancer progression. This review will explore the biochemical characteristics of mesotrypsin and structural insights into its specificity, function, and inhibition.     

A specific subset of transient receptor potential vanilloid-type channel subunits in Caenorhabditis elegans endocrine cells function as mixed heteromers to promote neurotransmitter release

Transient receptor potential (TRP) channel subunits form homotetramers that function in sensory transduction. Heteromeric channels also form, but their physiological subunit compositions and functions are largely unknown. We found a dominant-negative mutant of the C. elegans TRPV (vanilloid-type) subunit OCR-2 that apparently incorporates into and inactivates OCR-2 homomers as well as heteromers with the TRPV subunits OCR-1 and -4, resulting in a premature egg-laying defect. This defect is reproduced by knocking out all three OCR genes, but not by any single knockout. Thus a mixture of redundant heteromeric channels prevents premature egg laying. These channels, as well as the G-protein G alpha(o), function in neuroendocrine cells to promote release of neurotransmitters that block egg laying until eggs filling the uterus deform the neuroendocrine cells. The TRPV channel OSM-9, previously suggested to be an obligate heteromeric partner of OCR-2 in sensory neurons, is expressed in the neuroendocrine cells but has no detectable role in egg laying. Our results identify a specific set of heteromeric TRPV channels that redundantly regulate neuroendocrine function and show that a subunit combination that functions in sensory neurons is also present in neuroendocrine cells but has no detectable function in these cells.     

Regulation of cytosolic phospholipase A2 in rat endometrial stromal cells: the role of epidermal growth factor

The effect of epidermal growth factor on the levels of cytosolic phospholipase A2 mRNA and protein in cultured rat endometrial stromal cells isolated from uteri sensitized for the decidual cell reaction was examined. Treatment with epidermal growth factor increased the steady-state cytosolic phospholipase A2 mRNA and protein levels as demonstrated by Northern and Western blot analyses, respectively. Immunocytochemical analysis demonstrated an increase of cytosolic phospholipase A2 protein in most cells, as opposed to a small subpopulation of cells in culture. These results show that epidermal growth factor causes an increase in steady-state cytosolic phospholipase A2 mRNA and protein levels in rat endometrial stromal cells from uteri sensitized for the decidual cell reaction. Epidermal growth factor receptor ligands may regulate cytosolic phospholipase A2 and thus prostaglandin production in the endometrial stromal cells during implantation.     

Validation of a total testosterone assay using high-turbulence liquid chromatography tandem mass spectrometry: Total and free testosterone reference ranges

Accurate measurement of testosterone concentration is of critical importance when diagnosing and treating male hypogonadism, congenital adrenal hyperplasia, premature or delayed puberty, and androgen excess in polycystic ovary syndrome or other virilizing conditions. However, some assays have inherent limitations and biases that affect measurement of low-testosterone values. Therefore, we developed a highly specific online mass spectrometry method. Sera were extracted online using high-turbulence flow liquid chromatography coupled to analytical HPLC and atmospheric pressure chemical ionization tandem mass spectrometry (HTLC-APCI-MS/MS). Analyte ions were monitored by multiple reaction monitoring (MRM). Total analysis time was 1.15 min per sample when using the multiplexing system. Testosterone concentrations were measured directly from 150 μL of serum or plasma without derivatization or liquid-liquid extraction. The lower limit of quantification was 0.3 ng/dL, and the assay was linear up to 2000 ng/dL. The method compared very well with an established RIA: y = 1.02x + 1.5, r² = 0.994. Comparison with a platform immunoassay confirmed the previously reported ICMA positive bias at low concentrations. Male and female adult and pediatric reference ranges were developed for this very sensitive and accurate high-throughput LC-MS/MS method. This method is suitable for measuring the expected low-testosterone concentrations seen in women, children, and hypogonadal males and for monitoring testosterone suppressive therapy in prostate cancer patients.     

Pharmacological modulation and differential regulation of the cardiac gap junction proteins connexin 43 and connexin 40

Gap junction channels provide the basis for the electrical syncytial properties of the heart as a communicating electrical network. Cardiac gap junction channels are predominantly composed of connexin 40 or connexin 43. The conductance of these channels (g(j)) can be regulated pharmacologically: substances which activate protein kinase C, protein kinase A or protein kinase G may alter Cx43 gap junction conductance. However, for PKC, this seems to be subtype specific. Thus, antiarrhythmic peptides can enhance g(j) via activation of PKCepsilon, while FGF-2 reduces g(j) via PKCepsilon. Lipophilic drugs can uncouple the channels. Besides an acute regulation of g(j), the expression of the cardiac connexins can also be regulated. A decrease in Cx43 with a concomitant increase in Cx40 has been found in end-stage failing hearts, while in renovascular hypertension, an increase in Cx43 has been described. Mediators like endothelin-1, angiotensin-II, TGF-beta, VEGF, and cAMP have been shown to increase Cx43. Interestingly, endothelin-1 and angiotensin-II increased Cx43 but did not affect Cx40 expression. In contrast, in humans suffering from atrial fibrillation (AF), the content in Cx40 can be enhanced while Cx43 was unaltered, although in several other studies, other changes of the cardiac connexins were found, which might be related to the type of AF. Regarding the role of calcium, the content in both Cx40 and Cx43 was decreased in cultured neonatal rat cardiomyocytes after 24 h administration of 100 nM verapamil. Thus, gap junctional channels can be affected pharmacologically either acutely by modulating gap junction conductance or chronically by altering gap junction protein expression. Interestingly, it appears that the expression of Cx43 and Cx40 can be differentially regulated.     

Vascular endothelial growth factor receptor-3 activity is modulated by its association with caveolin-1 on endothelial membrane

Vascular endothelial growth factor receptor-3 (VEGFR-3) is constitutively expressed in lymphatic vessels and transiently in endothelial cells of blood vessels during angiogenesis. Here we report that VEGFR-3 localizes in the caveolae membrane of endothelial cells and co-immunoprecipitates with caveolin-1. Caveolin-1 silencing or its depletion from the cell membrane by cholesterol increases VEGFR-3 autophosphorylation, suggesting that caveolin acts as a negative regulator of VEGFR-3 activity. Receptor activation induces caveolin-1 phosphorylation on tyrosine residues including tyrosine 14. Cell treatment with Src or Abl inhibitors PP2 or STI571, prior to receptor stimulation, affects caveolin-1 phosphorylation without affecting receptor autophosphorylation, suggesting that both Src and Abl are involved in VEGFR-3-dependent caveolin-1 phosphorylation. Caveolin-1 phosphorylation in Src/Fyn/Yes knockout cells demonstrated that Abl phosphorylates caveolin-1 independently from Src family members. These results suggest a functional interaction between VEGFR-3 and caveolin-1 to modulate endothelial cell activation during angiogenesis.