DEPRESSION OF ENDOTHELIAL NITRIC-OXIDE SYNTHASE BUT INCREASED EXPRESSION OF ENDOTHELIN-1 IMMUNOREACTIVITY IN RAT THORACIC AORTIC ENDOTHELIUM ASSOCIATED WITH LONG-TERM, BUT NOT SHORT-TERM, SYMPATHECTOMY

Recent pharmacological studies have shown that perivascular nerves can influence the development and function of vascular endothelial cells (ECs). However, morphological studies have not yet been carried out to investigate whether these functional changes are associated with chan ges in vasoactive substances in ECs. We used postembedding electron mi croscopy (EM) triple gold-labeling immunocytochemistry to study the ef fects of short-term sympathectomy (3 days after 6-hydroxydopamine [6-O HDA] treatment) and long-term sympathectomy (guanethidine and 8 days a fter 6-OHDA) on the distribution of vasoactive substances in ECs of th e rat thoracic aorta. The postembedding immunocytochemistry, which can detect levels of label in individual cells, showed that there was a s ignificant decrease in endothelial NO synthase (NOS3)-labeled, seroton in (5-HT)-labeled, and substance P (SP)-labeled, but a significant inc rease in endothelin-1 (ET-1)-labeled, gold particles in ECs after long -term, but not after short-term (3-day), sympathectomy. In conclusion, our results show that long-term sympathectomy causes an increase in E T-1 and decrease in NOS3, 5-HT, and SP immunoreactivity in ECs of the thoracic aorta. Our data also indicate that postembedding EM triple go ld-labeling immunocytochemistry is a valuable technique for quantitati ve studies of the content of vasoactive substances in ECs.