Distribution of sulfate in blood and between cerebrospinal fluid and plasma in vivo

¹ Department of Biological Chemistry, Harvard Medical School, Boston, Massachusetts

The distribution of carrier-free radiosulfate in body fluids was studied after intravenous and intrathecal administration of Na₂S³⁵O₄ to dogs and rabbits. Plasma radiosulfate exchanged with red blood cell sulfate in 30–60 minutes to give ratios of distribution of approximately 0.40 in the circulating blood of rabbits and dogs. Exchange of plasma radiosulfate with cerebrospinal fluid sulfate was complete in 2–3 hours. Intrathecally administered radiosulfate exchanged with plasma and body sulfate in 5–8 hours. The ratio of the concentration of radiosulfate in cerebrospinal fluid to its concentration in plasma was found to reach a steady-state value of approximately 0.12–0.18 in anesthetized dogs. The rate constants of the penetration of radiosulfate from plasma water into red blood cell and cerebrospinal fluid water was found to be K = 0.03 and K = 0.01/ min., respectively, after intravenous injections of Na₂S³⁵O₄ into dogs. The route of administration of the tracer did not alter the final distribution ratios appreciably.