Citations

Transforming growth factor α (TGF-α) is produced by and required for the growth of epithelial cells and is angiogenic in vivo. Since epidermal hyperplasia and angiogenesis are hallmarks of psoriasis, TGF-α gene expression was analyzed in epidermal biopsies of normal and psoriatic skin. TGF-α messenger RNA and protein are much more abundant in lesional psoriatic epidermis than in normal-appearing skin of psoriatic patients or in normal epidermis. In contrast, messenger RNA levels of transforming growth factor β1 (TGF-β1), which inhibits epithelial cell growth, are not significantly different in normal, uninvolved, and lesional psoriatic epidermis. Thus, psoriatic epidermal hyperplasia may involve increased expression of a keratinocyte mitogen (TGF-α) rather than deficient expression of a growth inhibitor (TGF-β1).

Aggregating autologous platelets caused contraction of isolated rings of canine left circumflex arteries. The contractions were augmented after removal of the endothelium and were attenuated by serotonergic antagonists. During contraction caused by prostaglandin F 2α , aggregating platelets caused a transient increase in tension followed by a profound relaxation of arteries with endothelium, but caused only further contraction of arteries without endothelium. These observations demonstrate the importance of the vascular endothelium in opposing the constriction of coronary vessels caused by 5-hydroxytryptamine and other substances released from aggregating platelets.