Gender differences in tail-skin flushing induced by nitrates and phosphodiesterase type 5 inhibitors in a climacteric mouse model.

Flushing is one of the most common vasodilation-related adverse effects associated with both nitrates and phosphodiesterase type 5 (PDE5) inhibitors. The present study aimed to investigate the effects of orchidectomy and ovariectomy on isosorbide dinitrate-, sildenafil-, vardenafil- and tadalafil-induced flushing of tail-skin in mice. Both orchidectomy and ovariectomy markedly increased the tail-skin temperature, a good parameter of flushing, induced by isosorbide dinitrate (500 microg/kg, i.p.). These observations suggest that both testosterone withdrawal and estrogen withdrawal are risk factors for isosorbide dinitrate-induced flushing. In contrast, sildenafil (100 mg/kg, p.o.)-, vardenafil (10 mg/kg, p.o.)- and tadalafil (40 mg/kg, p.o.)-induced flushing of tail-skin in mice was aggravated by ovariectomy but not by orchidectomy. Orchidectomized male mice, but not ovariectomized female mice, showed significantly lower levels of PDE5 mRNA expression in tail artery compared with those of sham-operated mice. The present findings suggest that estrogen withdrawal, but not testosterone withdrawal, is a risk factor for PDE5 inhibitor-induced flushing. These gender differences in the vascular adverse reactions of PDE5 inhibitors may be interpreted as occurring due to differences in the levels of PDE5 mRNA expression in peripheral arteries.

Late deposition of elastin to vertical microfibrillar fibers in the presumptive dermis of the chick embryonic tarsometatarsus.

Fibrillin microfibrils are integral components of elastic fibers and serve as a scaffold for elastin deposition. However, microfibrillar fibers (MFs) are not necessarily committed to develop into so-called elastic fibers. In dermis, elastin-free oxytalan MFs originating from the dermoepidermal junction are continuous to elaunin-type MFs (with a small amount of elastin) in the deeper papillary dermis, whereas the reticular dermis contains elastic fibers, or MFs embedded largely in elastin. In this study, we have investigated temporospatial patterns of elastin deposition on the MFs in tarsometatarsal presumptive dermis. While the earliest expression of elastin was demonstrated immunohistochemically as early as embryonic day 4 (ED4) in the wall of cardiac outflow and pharyngeal arch arteries, its deposition in the tarsometatarsus was first detected at ED6 in the deeper mesenchyme and at ED13 in the subectodermal mesenchyme. In the latter tissue, MFs had been organized perpendicularly to the covering ectoderm by ED4, well before an overt accumulation of collagenous matrix. Elastin deposition was observed initially in a punctate manner at ED13 and afterward became continuous along MFs. However, a characteristic spaced array of subectodermal vertical MFs was disorganized by ED17. These findings suggest that elastin deposition in the subectodermal MFs is not deployed by continuous, orderly propagation from elastic fibers in the deeper mesenchyme but occurs de novo in multiple foci along vertical MFs. Moreover, the present chronology of elastin deposition indicates that subectodermal, elastin-free MFs function as a transient, but primary fibrous structure in the presumptive dermis before the accumulation of collagenous matrix.

Cellular origin of microfibrils explored by monensin-induced perturbation of secretory activity in embryonic primary cultures.

Fibrillin is a primary component of elastin-associated microfibrils. Since microfibrils are distributed rather ubiquitously in embryonic tissues, attention has focused on the types of cells responsible for producing fibrillin. To clarify this issue, we employed monensin-induced perturbation of secretory activity in embryonic primary cultures, as this would allow examination of both the secreted protein and the formation of extracellular fibrils in the same culture. Micromasses of avian limb bud mesoderm, its ectodermal covering and several explants from other sources were cultured in the presence and absence of monensin, and evaluated immunohistochemically using antibodies against fibrillin and cell lineage markers. The results indicated that monensin perturbation induced intracellular accumulation of fibrillin and prevented the formation of microfibrils. It was shown specifically that not only mesodermally derived fibrogenic cells and myogenic cells of skeletal and smooth muscle cell lineage, but also epithelial-type cells such as endothelial and ectodermal cells, are producers of fibrillin. This dual cellular origin of fibrillin at the ectomesenchymal interface is considered significant for understanding the formation and remodeling of microfibrils originating from the basal lamina.

Subectodermal microfibrillar bundles are organized into a distinct parallel array in the developing chick limb bud.

In this study, a unique fiber system in the subectodermal mesenchyme of the chick limb bud was visualized immunohistochemically with the use of a novel monoclonal antibody termed "FB1." This antibody stained a subset of extracellular fibers in the embryonic mesenchyme. Among the fibers visualized, those running perpendicularly to the limb bud ectoderm became progressively prominent in their thickness and length, and organized into a parallel array in the subectodermal region. This fiber system was distinct from that of major collagens, fibronectin, or tenascin. A molecule immunoprecipitated with FB1 comigrated with JB3 antigen, or chicken fibrillin-2. The fibers visualized immunohistochemically by FB1 and JB3 were indistinguishable from each other, and ultrastructurally appeared to be bundles composed of tubular-like microfibrils that originated directly from the ectodermal basal lamina. They lacked the amorphous deposits that are characteristic of elastin. A similar array of subectodermal fibers was also found in the developing axilla and some truncal regions, again well before the development of a definitive dermis. These findings suggest that a parallel array of subectodermal FB1-positive fibers constitutes a precocious fiber system in the presumptive dermis prior to the substantial formation of collagenous fibers. These fibers could be developmentally linked to oxytalan fibers, which are known to be present in the papillary dermis in mature cutaneous tissue.