Periarteritis nodosa in spontaneously hypertensive rats--immunohistological study and permeability test.

Spontaneously hypertensive rats develop periarteritis nodosa spontaneously with high incidence. Immunohistology of periarteritis nodosa reveals that fibrinogen constantly deposits in the wall of the diseased artery in exceptional combination with IgG but never with complement (C3). This fact suggests that periarteritis nodosa in spontaneously hypertensive rats may not be arteritis of immune complex type. Permeability test using mainly peroxidase as a tracer demonstrates that increased arterial permeability in spontaneously hypertensive rats is recognizable since 4 to 6 months of age without sexual difference in its intensity. In male spontaneously hypertensive rats periarteritis nodosa is observed in 6 of 11 and the arterial permeability increases more pronouncedly in the positive group, whereas 5 female spontaneously hypertensive rats of various ages are free from periarteritis nodosa irrespective of high arterial permeability. Therefore, high arterial permeability does not always lead to regular development of periarteritis nodosa especially in female spontaneously hypertensive rats.