The incidence and development of periarteritis nodosa in testicular arterioles and mesenteric arteries of spontaneously hypertensive rats.

We sought to clarify the incidence, vessel-size and age distribution of periarteritis nodosa in rats occurring as a vascular lesion in malignant hypertension. Stroke-prone spontaneously hypertensive and stroke-resistant spontaneously hypertensive rat strains were studied, as well as Wistar-Kyoto control rats. Mesenteric arteries and testicular arteries were examined histologically. Additionally, electron microscopy investigation was carried out on one stroke-prone hypertensive rat and one control. Periarteritis nodosa lesions were present in testicular arterioles in 57.1%, and mesenteric arteries in 28.6%, of stroke-prone hypertensive rats aged 9.5 mo. Lesion incidence at these sites was 100% and 60% respectively in 10 stroke-prone rats aged 15.5 mo, and 42.9% and 28.6% in stroke-resistant hypertensive rats aged 22.5 mo. In contrast, the incidence rate was 0% at both sites in stroke-resistant hypertensive rats aged 8 or 14.5 mo, and in control rats aged 9.5 or 25 mo. In stroke-prone rats, arteritis lesion counts (mean+/-SD) in testicular sections were 11.6+/-17 at age 9.5 mo and 96.3+/-60.9 at age 15.5 mo. In individual lesion scoring, arteritis was more severe in mesenteric arteries than in testicular arterioles. For arteriolar lesion distribution patterns in testicular sections, partial peripheral, partial peripheral plus central, and circumferential patterns were all noted. In conclusion, periarteritis nodosa in hypertensive stroke-prone rats occurs earlier in testicular arterioles, but attains greater severity in the mesenteric artery.