A quantitative investigation of microvascular changes in the thyroid glandafter infrared (IR) laser radiation

We present an ultrastructural study of thyroid capillaries in which 50-day- old rats Wistar rats, were irradiated with an infrared (IR) laser, (total d ose, 46.80 J/cm(2)), the tissue quantified 1 day after ending treatment and a quantitative capillary analysis carried out by light and electron micros copy. Light microscopy was used to calculate capillary volume density revea ling a significant increase in the irradiated rats. The quantitative measur ement of parameters by electron microscopy required a two stage analysis: L evel I, Electron Microscopy (Magnification x5,000); and Level II, Electron Microscopy (Magnification x26,000). At Level I, the following parameters we re measured in each capillary: capillary area, capillary diameter, luminal area, luminal diameter, endothelial area, nuclear area and mean endothelial thickness. At Level II, pinocytotic vesicle diameter and their numerical d ensity in endothelial cells were evaluated. Electron microscopic analysis r evealed an increased luminal area in the capillaries of the irradiated rats . They also presented a decrease in endothelial cell thickness and vesicula r diameter and an increase in vesicle numerical density. This latter increa se is indicative of presumptive changes in capillary permeability, but the possible functional significance of these morphological changes in the endo thelial cells requires further investigation.