Abstract-High doses of warfarin cause focal calcification of the elastic lamellae in the media of major arteries and in aortic heart valves in the rat. Aortic calcification was first seen after 2 weeks of warfarin treatment and progressively increased in density at 3, 4, and 5 weeks of treatment. By 5 weeks, the highly focal calcification of major arteries could be seen on radiographs and by visual inspection of the artery. The calcification of arteries induced by warfarin is similar to that seen in the matrix Gla protein (MGP)-deficient mouse, which suggests that warfarin induces artery calcification by inhibiting ␥-carboxylation of MGP and thereby inactivating the putative calcification-inhibitory activity of the protein. Warfarin treatment markedly increased the levels of MGP mRNA and protein in calcifying arteries and decreased the level of MGP in serum. Warfarin treatment did not affect bone growth, overall weight gain, or serum calcium and phosphorus levels, and, because of the concurrent administration of vitamin K, prothrombin times and hematocrits were normal. The results indicate that the improved warfarin plus vitamin K treatment protocol developed in this study should provide a useful model to investigate the role of MGP in preventing calcification of arteries and heart valves.

Abstract-The present studies demonstrate that growth and vitamin D treatment enhance the extent of artery calcification in rats given sufficient doses of Warfarin to inhibit ␥-carboxylation of matrix Gla protein, a calcification inhibitor known to be expressed by smooth muscle cells and macrophages in the artery wall. The first series of experiments examined the influence of age and growth status on artery calcification in Warfarin-treated rats. Treatment for 2 weeks with Warfarin caused massive focal calcification of the artery media in 20-day-old rats and less extensive focal calcification in 42-day-old rats. In contrast, no artery calcification could be detected in 10-month-old adult rats even after 4 weeks of Warfarin treatment. To directly examine the importance of growth to Warfarin-induced artery calcification in animals of the same age, 20-day-old rats were fed for 2 weeks either an ad libitum diet or a 6-g/d restricted diet that maintains weight but prevents growth. Concurrent treatment of both dietary groups with Warfarin produced massive focal calcification of the artery media in the ad libitum-fed rats but no detectable artery calcification in the restricted-diet, growth-inhibited group. Although the explanation for the association between artery calcification and growth status cannot be determined from the present study, there was a relationship between higher serum phosphate and susceptibility to artery calcification, with 30% higher levels of serum phosphate in young, ad libitum-fed rats compared with either of the groups that was resistant to Warfarin-induced artery calcification, ie, the 10-month-old rats and the restricted-diet, growth-inhibited young rats. This observation suggests that increased susceptibility to Warfarin-induced artery calcification could be related to higher serum phosphate levels. The second set of experiments examined the possible synergy between vitamin D and Warfarin in artery calcification. High doses of vitamin D are known to cause calcification of the artery media in as little as 3 to 4 days. High doses of the vitamin K antagonist Warfarin are also known to cause calcification of the artery media, but at treatment times of 2 weeks or longer yet not at 1 week. In the current study, we investigated the synergy between these 2 treatments and found that concurrent Warfarin administration dramatically increased the extent of calcification in the media of vitamin D-treated rats at 3 and 4 days. There was a close parallel between the effect of vitamin D dose on artery calcification and the effect of vitamin D dose on the elevation of serum calcium, which suggests that vitamin D may induce artery calcification through its effect on serum calcium. Because Warfarin treatment had no effect on the elevation in serum calcium produced by vitamin D, the synergy between Warfarin and vitamin D is probably best explained by the hypothesis that Warfarin inhibits the activity of matrix Gla protein as a calcification inhibitor. High levels of matrix Gla protein are found at sites of arte...

Abstract-The present experiments were carried out to test the hypothesis that artery calcification is linked to bone resorption by determining whether the selective inhibition of bone resorption with the bisphosphonates alendronate and ibandronate will inhibit artery calcification. Artery calcification was first induced by treatment of 42-day-old male rats with warfarin, a procedure that inhibits the ␥-carboxylation of matrix Gla protein and has been shown to cause extensive calcification of the artery media within 2 weeks. These experiments revealed that ibandronate (0.05 mg ⅐ kg) completely inhibited calcification of all arteries and heart valves examined after 2 and 4 weeks of warfarin treatment. A 10-fold lower dose of alendronate reduced artery calcification by 50% (PϽ0.005). These bisphosphonate doses are comparable to those that inhibit bone resorption in rats of this age. More rapid artery calcification was induced by treatment with warfarin together with high doses of vitamin D, a procedure that causes extensive artery calcification by 84 hours. Alendronate and ibandronate again completely inhibited calcification of all arteries and heart valves examined. The subcutaneous doses of alendronate and ibandronate necessary to inhibit artery calcification are comparable to the daily subcutaneous doses of these drugs that have previously been shown to inhibit bone resorption in rats of the same age, with 50% inhibition of artery calcification at 20 g alendronate ⅐ kgBisphosphonate treatment did not affect serum calcium and phosphate, and so the inhibition of artery calcification cannot be due to a simple lowering of the serum calcium phosphate ion product. We conclude that bisphosphonates inhibit the calcification of arteries and heart valves at doses comparable to the doses that inhibit bone resorption. These results support the hypothesis that artery calcification is linked to bone resorption. The mechanism of this linkage remains to be established, however, and an alternative explanation for the present results is also considered. Key Words: artery calcification Ⅲ bisphosphonates Ⅲ bone resorption Ⅲ alendronate Ⅲ ibandronate T he present experiments were carried out to test the hypothesis that artery calcification is linked to bone resorption. This hypothesis originated in experiments we carried out to understand the factors that enhance artery calcification in rats treated with high doses of warfarin, a vitamin K antagonist that inhibits the ␥-carboxylation of matrix Gla protein (MGP) and thereby causes extensive calcification of the elastic lamella in the artery media and in heart valves, 1 a pattern of calcification also seen in the MGP gene knockout mouse. 2 In the course of these studies, we observed that warfarin treatment induces artery calcification to the greatest extent in young, rapidly growing rats and that adult rats are completely resistant to warfarininduced artery calcification. 3 The susceptibility of young rats to warfarin-induced artery calcification is related to growth and not age per s...

A b s t r a c t Electronic laboratory interfaces can significantly increase the value of ambulatory electronic health record (EHR) systems by providing laboratory result data automatically and in a computable form. However, many ambulatory EHRs cannot implement electronic laboratory interfaces despite the existence of messaging standards, such as Health Level 7, version 2 (HL7). Among several barriers to implementing laboratory interfaces is the extensive optionality within the HL7 message standard. This paper describes the rationale for and development of an HL7 implementation guide that seeks to eliminate most of the optionality inherent in HL7, but retain the information content required for reporting outpatient laboratory results. A work group of heterogeneous stakeholders developed the implementation guide based on a set of design principles that emphasized parsimony, practical requirements, and near-term adoption. The resulting implementation guide contains 93% fewer optional data elements than HL7. This guide was successfully implemented by 15 organizations during an initial testing phase and has been approved by the HL7 standards body as an implementation guide for outpatient laboratory reporting. Further testing is required to determine whether widespread adoption of the implementation guide by laboratories and EHR systems can facilitate the implementation of electronic laboratory interfaces.