Glomic cells and blood vessels in the hyperplastic carotid bodies of spontaneously hypertensive rats.

Carotid bodies from 21 normotensive Wistar albino rats were compared with those from 20 spontaneously hypertensive rats of the Okamoto strain. From serial histological sections the volume of the carotid bodies was estimated by Simpson's rule. Differential and absolute cell counts were also performed on the chief and elongated cells which surround them. The glomic vasculature was examined by light and electron microscopy. Although the carotid bodies of Okamoto rats were nearly three times as large as those of Wistar rats of comparable body weight, there was no difference in the proportion of the two types of cell. The organisation of glomic cells was also similar in the two strains. The main carotid body artery consists of a muscular tube with a valve-like cushion at its orifice. In the Okamoto rats branches of this artery were occluded by intimal proliferations of myofibroblasts embedded within a copious, loose matrix of acid mucopolysaccharide ground substance. These proliferations appeared to originate from intimal pads situated at the origins of many glomic arteries and arterioles. These findings are in sharp contrast to those in the hyperplastic human carotid body.