Maternal and postnatal vitamin D ingestion influences rat aortic structure, function and elastin content.

Abstract

OBJECTIVES: Subtle impairment of fetal nutrition appears to predict hypertension and atherosclerosis in adults. It has been hypothesised that impaired aortic elastogenesis is the initiating step in adult hypertension and aortic aneurysms. Vitamin D has been shown to inhibit elastin synthesis by cultured smooth muscle cells. Here we have investigated, in rats, the hypothesis that increased exposure to vitamin D during gestation and in the postnatal period alters aortic elastin content and aortic function. METHODS: Nine breeding pairs of Sprague-Dawley rats were allocated to one of three diets containing 3000 (control group), 6000 (low dose) or 12,000 (high dose) IU/kg vitamin D during pregnancy and lactation. Male pups were continued on the same diet until 6 weeks of age. Aortic elastin content was assessed by measuring desmosine+isodesmosine content using capillary zone electrophoresis. Transverse aortic sections were used for quantification of elastic lamellae and morphometric analysis. The contractility of aortic rings was assessed in an organ bath preparation. RESULTS: The desmosine+isodesmosine content of the abdominal aorta of 6-week-old male pups, was 14.1, 10.0 and 10.1 nmol/mg dry weight in the control (n=20), low- (n=23) and high-dose (n=15) groups, respectively (P=0.007). The median number of elastic lamellae of the distal thoracic aorta was 8.25, 7.13 and 6.88 in the control, low-dose and high-dose groups, respectively (P<0.001). There were no significant differences in aortic cross-sectional areas or media:adventitia ratios. The mean peak tension of aortic rings, in response to phenylephrine, was 1.3 g, 1.12 g and 0.87 g in the control, low- and high-dose groups respectively (P=0.002). CONCLUSION: In rats, exposure to increased amounts of vitamin D during gestation and early life results in a reduction of aortic elastin content, number of elastic lamellae in the aorta and force generation in aortic rings.