First Cryophotometric Measurements of the HbO₂-Saturation in the Cat Carotid Body

Abstract

The cryophotometric method developed by Grunewald and Lübbers (1976) to define oxygen saturation of haemoglobin in blood vessels is suitable for determination of oxygen distribution within tissues. We therefore applied this method to the Glomus caroticum of the cat in order to verify the PO₂ distribution found by Acker et al (1971) in the carotid body tissue. Experiments were done on spontaneously breathing cats, anaesthetized with sodium pentobarbital (40–60 mg/kg). After preparation of the right carotid body and with controlled blood pressure, expiratory CO₂, tidal volume and arterial blood gases, the glomus caroticum was quickly frozen by Freon gas cooled in liquid nitrogen. The first figure shows such an experiment. Before the carotid body was removed the animal was ventilated with 5% O₂ in N₂. The tidal volume increased and consequently the expiratory CO₂ decreased. Blood pressure also decreased slightly. After examination of the blood gases the right carotid body region was quick-frozen as described above and excised. The whole procedure is quick and local and the animal does not show any reaction in blood pressure or respiration. This suggests that we are able to fix an actual physiologic state of the carotid body without disturbing the whole animal.