Evaluation of the Ca2+ distribution in aortic tissue of spontaneously hypertensive and normotensive rats.

In the present study, particle-induced X-ray emission (PIXE) was used to get information on the spatial distribution of Ca2+ in aortas of spontaneously hypertensive rats (SHR) and normotensive controls aged 1 week, 4 weeks, and 12 weeks. To differentiate changes in Ca2+ metabolism in hypertensive arteries from secondary phenomena due to the arteriosclerosis, the animals were examined in the earliest stage of hypertension. It was found that the Ca2+ content was not elevated in the aortic smooth muscle of SHR aged 1 week (n = 11), as compared to normotensive controls (n = 10) (186.8 +/- 89.9 micrograms Ca2+/g tissue v 254.0 +/- 173.3 micrograms Ca2+/g). The Ca2+ content was raised (P less than .05) in the aortic smooth muscle of SHR aged 4 weeks (n = 13), as compared to 12 WKY rats (4 weeks) (726.0 +/- 130.4 micrograms Ca2+/g tissue v 440.3 +/- 214.4 micrograms Ca2+/g) and in 17 SHR (3 months), as compared to 13 WKY rats, respectively (3390.1 +/- 729.9 micrograms Ca2+/g tissue v 1632.1 +/- 569.5 micrograms Ca2+/g). The results confirm the age-related increase in the arterial Ca2+ content in normotensive rats and demonstrate additionally that this age-related rise in arterial Ca2+ content is accelerated in SHR.