Figure 1. Effect of osmotic changes on [Ca²⁺]c in cultured chemoreceptor cells obtained from rat carotid bodies.

Decreasing osmolality from the control level of 300 mosmol kg⁻¹ to 250 mosmol kg⁻¹ induced a sustained (A, n = 8) or transient rise (B, n = 11) in [Ca²⁺]_c, while elevating osmolality to 350 mosmol kg⁻¹ (C, n = 11) had no effect. The osmotic concentration was adjusted by changing the sucrose concentration. [Ca²⁺]_c was estimated by fluorimetry in cells preloaded with Indo-1. [Ca²⁺]_c is indicated by the ratio (R) of emitted light at 400 and 500 nm, respectively. Hypercapnic acidosis (20 % CO₂, pH 6.8) was applied as a test stimulus.