Additional evidence that the sympathetic nervous system regulates the vessel wall release of tissue plasminogen...

It is established that sympathetic neurons can synthesize, transport and store tissue plasminogen activator (t-PA) within axon terminals in the smooth muscle of vessel walls. Moreover, sympathetic excitations (e.g. physical and mental stress) are known to induce an acute release of t-PA into the circulation. However, relatively little is known about the nature and extent of sympathetic nervous system involvement in the release process. We inquired whether a chemical sympathectomy will alter the release of t-PA into the blood, and the intrinsic release of stored t-PA from isolated whole vessel explants. A long-term sympathectomy was induced in adult Sprague-Dawley rats by injection of guanethidine during a 5-week course. The destruction of ganglion neurons and vessel wall axons was verified immunohistochemically. t-PA release was assayed as the free activity in hind limb plasma and explant culture medium. Following sympathectomy: (i) the basal t-PA activity in plasma was 70% less than controls (2.92 +/- 1.96 versus 9.33 +/- 1.72 IU/ml;