High sensitivity of hypertensive aortic myocytes to norepinephrine and angiotensin.

Single-mass primary cultures were used for as long as 5 wk as the source of subcultured vascular smooth muscle cells for the study of their change of shape on the addition of agonists. We have compared the responses to angiotensin II, vasopressin, norepinephrine, and serotonin of myocytes derived from three different areas or the thoracic aorta (aortic arch and midthoracic and diaphragm areas) of adult Wistar-Kyoto normotensive rats (WKY) and spontaneously hypertensive rats (SHR). Once in secondary culture, vascular myocytes displayed different mean sizes according to their origin along the organ, as previously described in freshly dispersed aortic myocyte suspensions. Responses of the cells from the area of the aortic arch of both strains had the maximal amplitude to all agonists. Angiotensin and norepinephrine were more potent on myocytes derived from the three areas in SHR than in WKY. As this hypersensitivity persisted even after 5 wk in culture, it is believed to be pressure independent and thus might have a genetic rather than an adaptive origin.