Morphology of thyroid vascular casts of hypertensive rats

Thyroid vascular casts were made by injecting a resin, Mercox, into 3 types of hypertensive rats (spontaneously hypertensive rats, SHR, stroke-prone SHR, SHRSP, malignant SHRSP, M-SHRSP), and the vascular casts were observed by scanning electron microscopy (SEM). There was no difference in the general morphology of the vascular casts between SHR and the control (Wistar Kyoto rats, WKY). However, the density and the diameter of blood vessels in SHRSP and M-SHRSP were significantly different from those in WKY, and abnormal vasculatures that formed protrusions with free endings were observed in M-SHRSP. It was concluded that thyroid vascular networks in hypertensive rats were transformed into abnormal formations with decreased capillary diameter in parallel with the progress of hypertension.