Age-dependent increase in arterial smooth muscle calcium in spontaneously hypertensive rats

Alterations in cellular calcium metabolism in essential hypertensive and in the SHR have been described. In the present study, particle-induced X-ray emission (PIXE) was used to get some 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. It was found that the Ca2+ content was not elevated in the aortic smooth muscle of SHR aged 1 week (n = 9) as compared to normotensive controls (n = 8) (186.8 +/- 89.9 micrograms Ca2+/g tissue vs 254.0 +/- 73.7 micrograms Ca2+/g tissue. The Ca2+ content was significantly raised in the aortic smooth muscle of SHR aged 4 weeks (n = 9) as compared to 4-weeks-old WKY rats (n = 12) (726.0 +/- 130.4 Ca2+/g tissue vs 440.3 +/- 214.4 Ca2+ micrograms/g tissue and in SHR aged 3 months (n = 15) as compared to WKY rats (n = 12), respectively (3317.0 +/- 734.0 micrograms Ca2+/g tissue vs. 1632.0 +/- 569.6 micrograms Ca2+/g tissue). 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.