Carotid and aortic bodies in chronically anemic normotensive and spontaneously hypertensive rats

Abstract

Overactivity of the carotid body chemoreceptors along with the enlargement of chemoreceptor tissue were found in spontaneously hypertensive rats of Okamoto-Aoki strain (SHR). The purpose of the present study was to answer the question whether the aortic bodies were also enlarged in SHR. However, because aortic bodies, unlike carotid ones, are sensitive to oxygen content another question arose: do aortic bodies undergo hypertrophy in chronic anemia? Twenty-three spontaneously hypertensive rats of Okamoto-Aoki strain (SHR) and 24 normotensive Wistar rats (NCR) were maintained on low-iron food from the age of 3 weeks. In seven 10-week-old anemic SHR regular diet was substituted (transiently anemic SHR). Blood pressure measurements and hemoglobin were measured every second week. The animals were killed at the age of 18 weeks. Light microscopic studies of the carotid and aortic bodies were performed and volumes of chemoreceptor tissues were determined from serial sections. The eight SHR on low-iron diet exhibited lower hemoglobin concentration than their normotensive counterparts. In the anemic SHR blood pressure was lower than in control SHR, whereas blood pressure did not differ between the anemic and control NCR. Restoration of normal values of hemoglobin in the anemic SHR was followed by only a slight increase in blood pressure. The carotid bodies volumes were 2.5–3 times larger in the SHR than in NCR. The volumes of carotid bodies both of the SHR and NCR were influenced neither by blood pressure nor by hemoglobin concentration. The aortic bodies were more numerous in SHR than in NCR. Enlargement of aortic bodies found in the anemic SHR was not visible in the transiently anemic SHR. The aortic bodies of NCR were not affected by decreased hemoglobin concentration. Less severe anemia not followed by any changes in blood pressure in the NCR is a plausible explanation of the lack of enlargement of aortic bodies in these rats.