The Effects of Posterior Pituitary Extracts on Water Balance in Bufo Carens and Xenopus Laevis, together with some General Considerations of Anuran Water Economy

Abstract

1. The effects of pitressin and pitocin on water balance in Bufo carens and Xenopus laevis have been investigated. Bufo carens is most sensitive to pitressin, and shows an increased water uptake together with a well-marked anti-diuretic response. Xenopus reacts equally to the two extracts by an increase in water uptake, but there is no anti-diuresis. 2. The effects of pitressin and pitocin in causing lymph accumulation and resorbtion of fluid from the bladder have been studied in Bufo regularis. Pitressin has the greater effect, and there are indications of seasonal variations in the magnitude of the response. 3. The normal rates of water uptake of B. regularis, B. carens and Xenopus laevis have been measured. The two species of Bufo take up water rapidly, but Xenopus does so much more slowly. After desiccation the water uptake of Bufo regularis increases very considerably. This does not occur in Xenopus. 4. There is a large weight increase after injection of posterior pituitary extracts in Bufo regularis and B. carens, but not in Xenopus laevis. The findings of other workers on the magnitude of the weight increase after posterior pituitary injections are summarized. 5. The results are discussed in relation to the identity of the active principles of the anuran posterior pituitary and to the biological significance of the responses.