Moll, Johann C.

The rates of disappearance D2O, Na22/24 and K42 from the arterial blood were determined in 17 dogs following rapid injection of the isotopes into the femoral and portal veins. Differences between systemic and portal venous injections were significant during the early phases of the disappearance of the isotopes (P < 0.05). Systemic insorption was simulated by continuous intravenous injection of D2O, Na22, and K42 at known rates into the femoral vein. The appearance of the isotopes in the arterial blood was determined repeatedly during and after their injection. The rate of injection (simulated insorption) was calculated using the mean systemic arterial disappearance rate. The differences between the calculated and actual rates of injection were insignificant. When portal insorption was simulated by constant injection of the isotope into the portal vein, the calculated rate of injection was not significantly different from the actual rate if the mean portal arterial disappearance curve was used in the calculation. When the systemic arterial disappearance curve was utilized, the calculated rate of injection was slightly faster than the actual rate. Submitted on July 11, 1962

This study was undertaken to determine rates of insorption of radiosodium and radiopotassium from secreting and nonsecreting stomachs of rats. The methods employed have been described previously. Insorption of radiosodium from gastric contents to blood was always faster in nonsecreting than in acid-secreting stomachs. At the end of 15, 30, and 45 min the mean percentages insorbed from stomachs secreting acid were 1.6, 3.1, and 4.5, whereas from stomach not secreting acid the mean percentages were 5.8, 9.3 and 11.7, respectively. In contrast, the rate of insorption of radiopotassium was unaffected by presence or absence of acid. Its rate of insorption was uniformly low and about equal to the rate of insorption of radiosodium from the secreting stomach. The results demonstrate that the rat's stomach, like that of man and dog, offers a barrier to insorption of sodium which is more pronounced when acid is being secreted and that insorption of potassium, though slow, is unaffected by acid and most likely is independent of insorption of sodium.

Rates of insorption of radiosodium and radiopotassium from the unobstructed small bowel of rats were determined and compared with those obtained by others in healthy humans. Insorption of the isotopes under study was estimated by integration of their rates of appearance in the blood after placement in the small bowel and their rates of disappearance from blood after injection into the circulation. The rates of disappearance from arterial blood were determined during separate tests. They followed an exponential pattern similar though not identical with that reported from other species by other investigators. Radiosodium was insorbed more rapidly than radiopotassium. Mean values indicated that 50% of administered radiosodium was insorbed within 6–7 min, whereas 26–27 min were required for insorption of 50% of the radiopotassium. The rate constant during insorption of the first 76% of the Na22 was 10.8% per min and that for insorption of 58% of the K42 was 2.7% per min.