Changes of euchromatin/heterochromatin ratios in cell nuclei of the aortic adventitia in diabetic rats.

The main objective of this study was to determine quantitatively euchromatin/heterochromatin (EU/HET) ratios of cell nuclei in the adventitia of 2 weeks streptozotocin induced diabetic rats combined with acridine orange (AO) ultracytochemistry. Specimens of the aorta above and below the orificium of the a. renalis were treated with AO and then prepared for electron microscopy. Images of 295 nuclei randomly selected from 180 ultrathin sections were analysed by a computer assisted image analyser method. The findings that surface areas of euchromatin portions and those of total nuclei are dependent variables (correlation coefficients 0.93-0.99), however, the EU/HET ratios and total surface areas are independent variables are essential prerequisites for an efficient application of this method. Determinations of EU/HET ratios revealed that populations of AO labeled cell nuclei consistently have higher ratios (2.17-3.38) than nuclei not labeled by AO (1.26-2.12). On the basis of 2583 nuclei counted AO positive cell nuclei were found to increase from 12% in control to 23% in diabetic rats. Changing EU/HET ratios are interpreted in terms of differential RNA synthetic activity enhanced in the early diabetic state. For these cells AO serves as a specific nuclear marker.