Evaluation of ultra-early and dose-dependent edema and ultrastructural changes in the myocyte during anti-hypertensive drug delivery in the spontaneously hypertensive rat model.

BACKGROUND

Quantifying dose-dependent ultra-early edema and ultrastructural changes in the myocyte after drug delivery is important for the development of new mixed calcium channel blockers (CCBs).

MATERIALS AND METHODS

Arterial cannulation was used to measure mean arterial pressure in real time; simultaneously, magnetic resonance imaging proton density mapping was used to quantify edema 5-55 min after the delivery of L-type CCBs, T- and L-type CCBs, and solvent to a spontaneously hypertensive rat model. Transmission electron microscopy was used to show ultrastructural changes in the myocyte.

RESULTS

Analysis of variance showed significant differences among the three groups in mean arterial pressure reduction (F = 246.36, P = 5.75E-25), ultra-early level of edema (ULE) (F = 175.49, P = 5.62E-22), and dose-dependent level of edema (DLE) (F = 199.48, P = 4.28E-23). Compared with the solvent's mean arterial pressure reduction (2.65±6.56±1.64), ULE (1.16±0.09±0.02), and DLE (0.0010±0.0001±0.0000), post hoc tests showed that T- and L-type CCBs had better mean arterial pressure reduction (90.67±11.58±2.90, P = 1.06E-24 vs. 68.34±15.19±3.80, P = 1.76E-12), lower ULE (1.53±0.14±0.04, P = 4.74E-9 vs. 2.08±0.18±0.04, P = 2.68E-22), and lower DLE (0.0025±0.0004±0.0001, P = 1.14E-11 vs. 0.0047±0.0008±0.0002, P = 2.10E-11) than L- type CCBs. Transmission electron microscopy showed that T- and L-type CCBs caused fewer ultrastructural changes in the myocytes after drug delivery than L-type CCBs.

CONCLUSION

T- and L-type CCBs produced less ultra-early and dose-dependent edema, fewer ultrastructural changes in the myocyte, and a greater antihypertensive effect. Proton density mapping combined with arterial cannulation and transmission electron microscopy allowed for quantification of ultra-early and dose-dependent edema, antihypertensive efficacy, and ultrastructural changes in the myocyte. This is important for the evaluation of induced vasodilatory edema.