The secretion of radioactive iodide by the stomach of the anaesthetized dog in relation to total gastric blood flow and to acid secretion

Lipschitz (1929) was probably the first to draw attention to the fact that the concentration of inorganic iodide in gastric juice was very much greater than that in plasma. The active transport of iodide by the gastric mucosa at physiological plasma-iodide levels has been studied since by many workers using radioactive iodide (see Brown-Grant, 1961, for references). In the majority of these studies no attempt has been made to express the rate of secretion of iodide in terms of the plasma content of iodide. One exception is the work of Howell & van Middlesworth (1956) who obtained values for the clearance of iodide by the stomach of anaesthetized dogs as high as 10-12 ml. of plasma/min after the injection of histamine. This value is of the same order as the rate of total gastric blood flow in anaesthetized dogs reported in an earlier studyfrom this laboratory (Cumming, Haigh, Harries & Nutt, 1963) and it appeared possible that measurement of the gastric iodide-clearance rate might provide an indirect index of the blood flow. Iodide clearance by the stomach and total gastric blood flow have been determined in anaesthetized dogs, both unstimulated and during the infusion of histamine. In addition the effects of adrenaline and noradrenaline on histamine-induced iodide secretion have been investigated and also the action of 5-hydroxytryptamine, both alone and together with histamine. A preliminary account of some of our findings has already been published (Brown-Grant, Cumming, Haigh & Harries, 1963).