Mechanical, Biochemical, and Structural Effects of Vitamin D Deficiency on the Chick Heart

The effects of vitamin D depriva tion on the chick heart were investi gated from three aspects: cardiac contractility (±dP/dT), intracellular high-energy phosphorus compounds, and structural differences. Four- week-old vitamin D-deficient chicks were divided into four groups: Group A served as the normal group and re ceived subcutaneous injections of cholecalciferol; Groups B and C were vitamin D-deficient hearts but per fused differently; Group D received daily subcutaneous injections of 5 μg of 1,25(OH)₂D₃. When the isolated spontaneously beating hearts (modi fied Langendorff preparation) were perfused with Krebs-Henseleit (KH) solution containing a calcium concen tration of 2.5mM, the myocardial contractility of the vitamin D-defi cient hearts was significantly in creased when compared with group A. After the isolated heart had beaten for one hour, the myocardial contractility in the vitamin D-defi cient hearts was found to decline to significantly lower values. Presacri fice administration of 1,25(OH)₂D₃ improved cardiac performance. Vita min D deficiency resulted in an en hanced rate of decline of the intracellular high-energy phosphorus compounds. No differences were found in the microscopic study. These observations suggest that vitamin D has a role in cardiac function.