[Measurement of water, DNA and collagen in different parts of the aorta in rats. Effect of hypertension].

Renovascular hypertension was induced in two-week rats (group HR, n = 6) and their aortas were studied 8 weeks later and compared with those from normotensive rats (group NR, n = 6). Total water content, DNA (fluorometric method) and collagen (calculated from hydroxyproline concentrations) concentrations were measured in the media of the arch, the descending thoracic aorta and the abdominal aorta. Water content and DNA content did not significantly change in the different parts of the aorta. The collagen content significantly decreased from the arch to the abdominal aorta, in NR as well as in HR group (p less than 0.01). Hypertension did not affect water content, DNA neither collagen content in the abdominal aorta. In the arch and in the descending thoracic aorta, hypertension was associated with an increase in collagen content (p less than 0.001), whereas the water and DNA contents did not significantly change. These results suggest that hypertension induced an increased collagen synthesis only in the thoracic aorta, this being more important in the arch than in the descending thoracic aorta. Responses to hypertension are different in thoracic and in abdominal part of rat aorta.