Background:
Heat pretreatment of swine carotid artery has been shown to increase ser16-heat shock protein 20 (hsp20) phosphorylation and suppress force, i.e., reduce force with only minimal reduction in ser19-myosin regulatory light chain (mrlc) phosphorylation.
Results:
We further investigated this response in intact histamine stimulated swine carotid artery rings. there was a heat threshold such that increased ser16-hsp20 phosphorylation and force suppression were observed between 43 degrees c and 46 degrees c. the increased ser16-hsp20 phosphorylation persisted up to 16 hours after 44.5 degrees c heat treatment. pretreatment of swine carotid media at 44.5 degrees c increased ser16-hsp20 phosphorylation without increases in [camp] or [cgmp], suggesting an alternate mechanism, perhaps phosphatase inhibition, for the increase in ser16-hsp20 phosphorylation. heat pretreatment at 47.5 degrees c reduced force by decreasing mrlc phosphorylation rather than by large increases in ser16-hsp20 phosphorylation. hsp20 phosphorylation at the putative pkc site did not change with any treatment.
Conclusion:
These results demonstrate that multiple mechanisms can induce force suppression that is correlated with ser16-hsp20 phosphorylation: 1) nitrovasodilators via cgmp, 2) forskolin via camp, and 2) thermal stress in a cyclic nucleotide independent manner.