SMALL HEAT-SHOCK PROTEINS AND VASOSPASM IN HUMAN UMBILICAL ARTERY SMOOTH-MUSCLE

Human umbilical artery smooth muscle is uniquely refractory to cyclic nucleotide-dependent vasorelaxation. Small heat shock proteins (HSPs) have been implicated as contractile regulatory proteins. Thus, we hypo thesized that alterations in the phosphorylation of small HSPs may con tribute to human umbilical artery smooth muscle vasospasm. Physiologic contractile responses were determined in a muscle bath and compared w ith phosphorylation events determined with whole-cell phosphorylation and 2-dimensional gel electrophoresis. Precontraction of bovine caroti d artery smooth muscle with serotonin followed by relaxation with fors kolin was associated with increases in the phosphorylation of HSP27 an d HSP20. Precontraction of umbilical artery with serotonin followed by forskolin treatment led to increases in the phosphorylation of HSP27. However, the umbilical artery smooth muscle did not relax, nor was th ere an increase in the phosphorylation of MSP20 with forskolin treatme nt. These data suggest that impaired cyclic nucleotide-dependent relax ation of umbilical artery smooth muscle is associated with a lack of p hosphorylation of HSP20.