Gastric function in Caiman crocodilus (Crocodylia: Reptilia). II. Effects of temperature on pH and proteolysis.

-1. In Caiman crocodilus, the pH of the gastric secretions during digestion may reach 1.2 in specimens kept between 20 and 30°C. C. crocodilus feeds and digests at 15°C, but the pH of gastric secretions did not drop below 1-8. 2. The gastric secretion increased in rate and hydrochloric acid concentration after injections of histamine (400 t~g/kg body weight, given in four hourly doses). The rate increased from 0.05 ml/kg, hr (resting rate, at 20°C) up to an average of 0.66 ml/kg, hr, at 30°C. 3. There is a latent period of 4-8 hr before the effects of histamine can be detected in tests carded out at 20, 25 and 30°C. 4. Peptic proteolysis of gastric secretions has pH optima in the range 2.0-2.6, when carded out at 25°C, using the hemoglobin method of Anson & Mirsky. 5. There were instances of more than one pH optimum for proteolysis, suggesting the occurence of isozymes. 6. Inside the range in which C. crocodilus feeds and digests, peptic proteolysis has an average Qlo of 1.62 (between 15 and 25°C) and of 1.50 (between 25 and 35°C). 7. In animals maintained at 25°C peptic proteolysis was highest at 24--48 hr after feeding.