Influence of age on carotid body size and arterial chemo receptor reflex effects in spontaneously hypertensive and normotensive rats
Pfeiffer, C.; Habeck J O.; Rotter, H.; Behm, R.; Schmidt, M.; Honig, A.
Biomedica Biochimica Acta 43(2): 205-214
1984
ISSN/ISBN: 0232-766X
Accession: 005679992
In normotensive Wistar rats of a random-bred strain, and in spontaneously hypertensive rats (SHR) of the Okamoto-Aoki-strain, the mean systemic arterial blood pressure, the pO2, pCO2, pH-values and the base excess of the arterial blood were measured during ventilating normal air as well as hypoxic (12.6% O2 in N2) and hyperoxic (100% O2) gas mixtures. The animals were anesthetized and breathed spontaneously; they aged 5-6, 15-20, 30-40 and 50-70 wk. The volume of their carotid bodies was determined morphometrically. When compared with the age-matched normotensive controls at an age of 5-6 wk, the SHR already exhibited slightly but significantly elevated blood pressures, but had equal carotid body size and arterial CO2 tension. In contrast, hypertensive animals in the established phase of hypertension (> 15 wk) showed greater carotid bodies and a highly significant respiratory alkalosis when compared with the corresponding age-group of the normotensive rats. The reactions of the mean systemic arterial blood pressure and the arterial pCO2 provoked by hypoxia and hyperoxia proved to be age-dependent in both the normotensive and hypertensive animals, but this influence of age was different in the 2 strains of rats. Alterations of arterial chemoreceptor structures and reflex effects found in the established phase of hypertension evidently are the result of this disease. When interpreting arterial chemoreceptor reflex effects in hypertensive humans and animals, the stage of hypertension apparently must be taken into account.